v2.72.0

This is a major release with several key additions, most notably being
the support for custom, mpv-style "user shaders" (.hook), giving us
access to a large variety of pre-existing user shaders such as RAVU,
FSRCNNX, Anime4K, SSimSuperRes, KrigBilateral, NNEDI3, and more.

In addition to this, major additions include a completely refactored and
fixed AV1 grain generation shader, support for Vulkan versions higher
than 1.0, support for GPU-based timers, and improved interop APIs for
both Vulkan and OpenGL, and new and improved aspect ratio handling.

Finally, this release also brings with it a major change to the way HDR
and SDR content are mapped between each other, including a new
tone-mapping function based on the industry-standard ITU-R BT.2390 EETF.

Additions:
- add `pl_swapchain_hdr_metadata`, to set HDR metadata on supported
  swapchains (currently only vulkan with `VK_EXT_hdr_metadata`)
- add support for vulkan versions higher than 1.0, communicated via the
  new fields `api_version` and `max_api_version`
- add support for GPU-assisted validation and best practices layers, via
  the new field `pl_vk_inst_params.debug_extra`
- add helper functions for working with `pl_rect`s, including new aspect
  ratio handling helpers (`pl_rect2df_aspect_*`)
- add field `pl_vulkan_params.device_uuid` to allow choosing the vulkan
  device by its UUID
- add function `pl_vulkan_hold_raw`, to hold images without actually
  transitioning its layout and access mode
- add function `pl_vulkan_import`, to allow directly re-using an
  existing VkDevice rather than creating a new one; this requires
  communicating metadata about how the device was created
- add field `pl_vulkan_params.features` to allow loading optional extra
  device features at device creation time
- add support for mpv-style custom user shaders (.hook), using the set
  of functions in `<libplacebo/shaders/custom.h>`
- add `pl_render_high_quality_params`, enabling debanding and EWA
  scaling
- add `pl_timer` GPU resource type and associated API functions,
  allowing the GPU execution time of shaders and texture transfer
  operations to be measured directly
- add `PL_SHADER_SIG_SAMPLER`, allowing generated sampling shaders to
  directly accept the sampler to use as function parameters
- add `pl_image_set_chroma_location` to automatically apply the correct
  chroma location to any subsampled planes
- add `PL_TONE_MAPPING_BT_2390`, a tone mapping function based on the
  EETF from ITU-R Report BT.2390 (and make it the default)
- add `pl_peak_detect_params.overshoot_margin` to help combat clipping
  on certain types of rapid scene fade-ins
- add `pl_sampler_type` to allow encoding non-standard sampler types
  such as sampler2DRect, and also generalize samplers to allow e.g.
  usampler2D or isampler3D
- add `pl_opengl_wrap` and `pl_opengl_unwrap`, to allow directly mapping
  between OpenGL textures and the `pl_tex` abstraction

Changes:
- deprecate `pl_image.width/height`, which are now inferred
  automatically from the actual planes
- `pl_vulkan_wrap` now takes a `pl_vulkan_wrap_params` struct instead of
  directly accepting its parameters, including new fields `sample_mode`
  and `address_mode` to configure the created sampler
- change `pl_dispatch_compute` to allow optionally passing in a
  simulated framebuffer width/height, which will be used to translate
  vertex attributes (if any)
- undefine disabled `config.h` features, instead of defining them as 0
- remove debanding from `pl_render_default_params`
- refactor HDR<->SDR mapping; PL_COLOR_REF_WHITE has been removed and
  replaced by PL_COLOR_SDR_WHITE (203 cd/m^2) and PL_COLOR_SDR_WHITE_HLG
  (75% HLG), respectively
- completely refactor pl_shader_av1_grain`, which now samples directly
  from the passed texture rather than requiring the color be pre-sampled
- `pl_render_image` now infers the image primaries based on resolution,
  rather than always hard-coding `PL_COLOR_SPACE_UNKNOWN` as BT.709
- change `pl_render_target.dst_rect` from `pl_rect2d` to `pl_rect2df`,
  allowing more accurate aspect ratio handling, and correctly compensate
  for subpixel scaling ratios
- require `python3-mako` as a dependency of the `vulkan` feature
- `pl_chroma_location_offset` now treats `PL_CHROMA_UNKNOWN` as
  `PL_CHROMA_LEFT`, the de-facto standard chroma location
- the default value of `pl_color_map_params.tone_mapping_algo` is now
  `PL_TONE_MAPPING_BT_2390`

Fixes and performance improvements:
- fix shader generation when the GLSL version is explicitly overridden
- properly mark some shader failures (`pl_shader_is_failed`)
- fix texture invalidation on OpenGL
- correctly respect `pl_swapchain_frame.flipped` in
  `pl_render_target_from_swapchain`
- correctly validate descriptor uniqueness in `pl_pass_create`
- skip redundant matrix multiplication in `pl_shader_encode_color`
  wherever possible
- work around driver bugs w.r.t out-of-order buffer offsets by sorting
  all buffer variables by offset
- fix edge cases in vulkan swapchain usage flag checks
- fix excessive CPU usage in `pl_tex_download`
- reduce the number of unnecessary GPU flushes caused by `pl_buf_poll`
- fix issue where blending did not work on some drivers (e.g. nvidia)
- make the framebuffer discard check more aggressive
- fix computation of anti-aliased resizable orthogonal filters, e.g.
  when downscaling using `pl_filter_lanczos`
- fix external image memory barriers for exclusive mode images
- fix failure path of `pl_swapchain_submit_frame`
- fix various GLSL compatibility issues with av1 grain generation
- reduce maximum vulkan memory allocation slab size to conform to AMD
  recommendations
- fix build error when lcms is not available
- fix double-application of texture scale for e.g. 10-bit content when
  using separable scalers
- fix a multitude of bugs affecting av1 grain generation, especially for
  chroma planes
- fix segfault on vulkan device oom
- fix invalid shader generation on some platforms
- fix a multitude of bugs, edge cases and subtle off-by-ones related to
  chroma scaling and plane alignment
- add fallback code for edge case w.r.t chroma scaling and gpu resource
  exhaustion
- correctly load VK_KHR_swapchain in all circumstances that require
  accessing its functions
- minimize fbo usage inside `pl_renderer`, by re-using unused fbos
- tweak the work group size for polar scaling to perform better on
  modern GPUs (tested on RDNA)
- transparently upgrade fragment shaders to compute shaders on
  environments with async compute
- pick a more reasonable size for the dummy gpu's `max_group_threads`
- forbid 10-bit linear transfer functions from vulkan swapchains
- fix segfault when re-executing previously failed shaders
- fix swapchain creation errors on GLES 2
- explicitly mark all shader resources as non-aliased
- correctly specify shader storage buffers as coherent for shaders that
  require them
- fix various memory barrier synchronization issues for opengl

v2.72.0-rc1

This is a major release with several key additions, most notably being
the support for custom, mpv-style "user shaders" (.hook), giving us
access to a large variety of pre-existing user shaders such as RAVU,
FSRCNNX, Anime4K, SSimSuperRes, KrigBilateral, NNEDI3, and more.

In addition to this, major additions include a completely refactored and
fixed AV1 grain generation shader, support for Vulkan versions higher
than 1.0, support for GPU-based timers, and improved interop APIs for
both Vulkan and OpenGL, and new and improved aspect ratio handling.

Finally, this release also brings with it a major change to the way HDR
and SDR content are mapped between each other, including a new
tone-mapping function based on the industry-standard ITU-R BT.2390 EETF.

Additions:
- add `pl_swapchain_hdr_metadata`, to set HDR metadata on supported
  swapchains (currently only vulkan with `VK_EXT_hdr_metadata`)
- add support for vulkan versions higher than 1.0, communicated via the
  new fields `api_version` and `max_api_version`
- add support for GPU-assisted validation and best practices layers, via
  the new field `pl_vk_inst_params.debug_extra`
- add helper functions for working with `pl_rect`s, including new aspect
  ratio handling helpers (`pl_rect2df_aspect_*`)
- add field `pl_vulkan_params.device_uuid` to allow choosing the vulkan
  device by its UUID
- add function `pl_vulkan_hold_raw`, to hold images without actually
  transitioning its layout and access mode
- add function `pl_vulkan_import`, to allow directly re-using an
  existing VkDevice rather than creating a new one; this requires
  communicating metadata about how the device was created
- add field `pl_vulkan_params.features` to allow loading optional extra
  device features at device creation time
- add support for mpv-style custom user shaders (.hook), using the set
  of functions in `<libplacebo/shaders/custom.h>`
- add `pl_render_high_quality_params`, enabling debanding and EWA
  scaling
- add `pl_timer` GPU resource type and associated API functions,
  allowing the GPU execution time of shaders and texture transfer
  operations to be measured directly
- add `PL_SHADER_SIG_SAMPLER`, allowing generated sampling shaders to
  directly accept the sampler to use as function parameters
- add `pl_image_set_chroma_location` to automatically apply the correct
  chroma location to any subsampled planes
- add `PL_TONE_MAPPING_BT_2390`, a tone mapping function based on the
  EETF from ITU-R Report BT.2390 (and make it the default)
- add `pl_peak_detect_params.overshoot_margin` to help combat clipping
  on certain types of rapid scene fade-ins
- add `pl_sampler_type` to allow encoding non-standard sampler types
  such as sampler2DRect, and also generalize samplers to allow e.g.
  usampler2D or isampler3D
- add `pl_opengl_wrap` and `pl_opengl_unwrap`, to allow directly mapping
  between OpenGL textures and the `pl_tex` abstraction

Changes:
- deprecate `pl_image.width/height`, which are now inferred
  automatically from the actual planes
- `pl_vulkan_wrap` now takes a `pl_vulkan_wrap_params` struct instead of
  directly accepting its parameters, including new fields `sample_mode`
  and `address_mode` to configure the created sampler
- change `pl_dispatch_compute` to allow optionally passing in a
  simulated framebuffer width/height, which will be used to translate
  vertex attributes (if any)
- undefine disabled `config.h` features, instead of defining them as 0
- remove debanding from `pl_render_default_params`
- refactor HDR<->SDR mapping; PL_COLOR_REF_WHITE has been removed and
  replaced by PL_COLOR_SDR_WHITE (203 cd/m^2) and PL_COLOR_SDR_WHITE_HLG
  (75% HLG), respectively
- completely refactor pl_shader_av1_grain`, which now samples directly
  from the passed texture rather than requiring the color be pre-sampled
- `pl_render_image` now infers the image primaries based on resolution,
  rather than always hard-coding `PL_COLOR_SPACE_UNKNOWN` as BT.709
- change `pl_render_target.dst_rect` from `pl_rect2d` to `pl_rect2df`,
  allowing more accurate aspect ratio handling, and correctly compensate
  for subpixel scaling ratios
- require `python3-mako` as a dependency of the `vulkan` feature
- `pl_chroma_location_offset` now treats `PL_CHROMA_UNKNOWN` as
  `PL_CHROMA_LEFT`, the de-facto standard chroma location
- the default value of `pl_color_map_params.tone_mapping_algo` is now
  `PL_TONE_MAPPING_BT_2390`

Fixes and performance improvements:
- fix shader generation when the GLSL version is explicitly overridden
- properly mark some shader failures (`pl_shader_is_failed`)
- fix texture invalidation on OpenGL
- correctly respect `pl_swapchain_frame.flipped` in
  `pl_render_target_from_swapchain`
- correctly validate descriptor uniqueness in `pl_pass_create`
- skip redundant matrix multiplication in `pl_shader_encode_color`
  wherever possible
- work around driver bugs w.r.t out-of-order buffer offsets by sorting
  all buffer variables by offset
- fix edge cases in vulkan swapchain usage flag checks
- fix excessive CPU usage in `pl_tex_download`
- reduce the number of unnecessary GPU flushes caused by `pl_buf_poll`
- fix issue where blending did not work on some drivers (e.g. nvidia)
- make the framebuffer discard check more aggressive
- fix computation of anti-aliased resizable orthogonal filters, e.g.
  when downscaling using `pl_filter_lanczos`
- fix external image memory barriers for exclusive mode images
- fix failure path of `pl_swapchain_submit_frame`
- fix various GLSL compatibility issues with av1 grain generation
- reduce maximum vulkan memory allocation slab size to conform to AMD
  recommendations
- fix build error when lcms is not available
- fix double-application of texture scale for e.g. 10-bit content when
  using separable scalers
- fix a multitude of bugs affecting av1 grain generation, especially for
  chroma planes
- fix segfault on vulkan device oom
- fix invalid shader generation on some platforms
- fix a multitude of bugs, edge cases and subtle off-by-ones related to
  chroma scaling and plane alignment
- add fallback code for edge case w.r.t chroma scaling and gpu resource
  exhaustion
- correctly load VK_KHR_swapchain in all circumstances that require
  accessing its functions
- minimize fbo usage inside `pl_renderer`, by re-using unused fbos
- tweak the work group size for polar scaling to perform better on
  modern GPUs (tested on RDNA)
- transparently upgrade fragment shaders to compute shaders on
  environments with async compute
- pick a more reasonable size for the dummy gpu's `max_group_threads`
- forbid 10-bit linear transfer functions from vulkan swapchains
- fix segfault when re-executing previously failed shaders

v2.72.0-rc2

This is a major release with several key additions, most notably being
the support for custom, mpv-style "user shaders" (.hook), giving us
access to a large variety of pre-existing user shaders such as RAVU,
FSRCNNX, Anime4K, SSimSuperRes, KrigBilateral, NNEDI3, and more.

In addition to this, major additions include a completely refactored and
fixed AV1 grain generation shader, support for Vulkan versions higher
than 1.0, support for GPU-based timers, and improved interop APIs for
both Vulkan and OpenGL, and new and improved aspect ratio handling.

Finally, this release also brings with it a major change to the way HDR
and SDR content are mapped between each other, including a new
tone-mapping function based on the industry-standard ITU-R BT.2390 EETF.

Additions:
- add `pl_swapchain_hdr_metadata`, to set HDR metadata on supported
  swapchains (currently only vulkan with `VK_EXT_hdr_metadata`)
- add support for vulkan versions higher than 1.0, communicated via the
  new fields `api_version` and `max_api_version`
- add support for GPU-assisted validation and best practices layers, via
  the new field `pl_vk_inst_params.debug_extra`
- add helper functions for working with `pl_rect`s, including new aspect
  ratio handling helpers (`pl_rect2df_aspect_*`)
- add field `pl_vulkan_params.device_uuid` to allow choosing the vulkan
  device by its UUID
- add function `pl_vulkan_hold_raw`, to hold images without actually
  transitioning its layout and access mode
- add function `pl_vulkan_import`, to allow directly re-using an
  existing VkDevice rather than creating a new one; this requires
  communicating metadata about how the device was created
- add field `pl_vulkan_params.features` to allow loading optional extra
  device features at device creation time
- add support for mpv-style custom user shaders (.hook), using the set
  of functions in `<libplacebo/shaders/custom.h>`
- add `pl_render_high_quality_params`, enabling debanding and EWA
  scaling
- add `pl_timer` GPU resource type and associated API functions,
  allowing the GPU execution time of shaders and texture transfer
  operations to be measured directly
- add `PL_SHADER_SIG_SAMPLER`, allowing generated sampling shaders to
  directly accept the sampler to use as function parameters
- add `pl_image_set_chroma_location` to automatically apply the correct
  chroma location to any subsampled planes
- add `PL_TONE_MAPPING_BT_2390`, a tone mapping function based on the
  EETF from ITU-R Report BT.2390 (and make it the default)
- add `pl_peak_detect_params.overshoot_margin` to help combat clipping
  on certain types of rapid scene fade-ins
- add `pl_sampler_type` to allow encoding non-standard sampler types
  such as sampler2DRect, and also generalize samplers to allow e.g.
  usampler2D or isampler3D
- add `pl_opengl_wrap` and `pl_opengl_unwrap`, to allow directly mapping
  between OpenGL textures and the `pl_tex` abstraction

Changes:
- deprecate `pl_image.width/height`, which are now inferred
  automatically from the actual planes
- `pl_vulkan_wrap` now takes a `pl_vulkan_wrap_params` struct instead of
  directly accepting its parameters, including new fields `sample_mode`
  and `address_mode` to configure the created sampler
- change `pl_dispatch_compute` to allow optionally passing in a
  simulated framebuffer width/height, which will be used to translate
  vertex attributes (if any)
- undefine disabled `config.h` features, instead of defining them as 0
- remove debanding from `pl_render_default_params`
- refactor HDR<->SDR mapping; PL_COLOR_REF_WHITE has been removed and
  replaced by PL_COLOR_SDR_WHITE (203 cd/m^2) and PL_COLOR_SDR_WHITE_HLG
  (75% HLG), respectively
- completely refactor pl_shader_av1_grain`, which now samples directly
  from the passed texture rather than requiring the color be pre-sampled
- `pl_render_image` now infers the image primaries based on resolution,
  rather than always hard-coding `PL_COLOR_SPACE_UNKNOWN` as BT.709
- change `pl_render_target.dst_rect` from `pl_rect2d` to `pl_rect2df`,
  allowing more accurate aspect ratio handling, and correctly compensate
  for subpixel scaling ratios
- require `python3-mako` as a dependency of the `vulkan` feature
- `pl_chroma_location_offset` now treats `PL_CHROMA_UNKNOWN` as
  `PL_CHROMA_LEFT`, the de-facto standard chroma location
- the default value of `pl_color_map_params.tone_mapping_algo` is now
  `PL_TONE_MAPPING_BT_2390`

Fixes and performance improvements:
- fix shader generation when the GLSL version is explicitly overridden
- properly mark some shader failures (`pl_shader_is_failed`)
- fix texture invalidation on OpenGL
- correctly respect `pl_swapchain_frame.flipped` in
  `pl_render_target_from_swapchain`
- correctly validate descriptor uniqueness in `pl_pass_create`
- skip redundant matrix multiplication in `pl_shader_encode_color`
  wherever possible
- work around driver bugs w.r.t out-of-order buffer offsets by sorting
  all buffer variables by offset
- fix edge cases in vulkan swapchain usage flag checks
- fix excessive CPU usage in `pl_tex_download`
- reduce the number of unnecessary GPU flushes caused by `pl_buf_poll`
- fix issue where blending did not work on some drivers (e.g. nvidia)
- make the framebuffer discard check more aggressive
- fix computation of anti-aliased resizable orthogonal filters, e.g.
  when downscaling using `pl_filter_lanczos`
- fix external image memory barriers for exclusive mode images
- fix failure path of `pl_swapchain_submit_frame`
- fix various GLSL compatibility issues with av1 grain generation
- reduce maximum vulkan memory allocation slab size to conform to AMD
  recommendations
- fix build error when lcms is not available
- fix double-application of texture scale for e.g. 10-bit content when
  using separable scalers
- fix a multitude of bugs affecting av1 grain generation, especially for
  chroma planes
- fix segfault on vulkan device oom
- fix invalid shader generation on some platforms
- fix a multitude of bugs, edge cases and subtle off-by-ones related to
  chroma scaling and plane alignment
- add fallback code for edge case w.r.t chroma scaling and gpu resource
  exhaustion
- correctly load VK_KHR_swapchain in all circumstances that require
  accessing its functions
- minimize fbo usage inside `pl_renderer`, by re-using unused fbos
- tweak the work group size for polar scaling to perform better on
  modern GPUs (tested on RDNA)
- transparently upgrade fragment shaders to compute shaders on
  environments with async compute
- pick a more reasonable size for the dummy gpu's `max_group_threads`
- forbid 10-bit linear transfer functions from vulkan swapchains
- fix segfault when re-executing previously failed shaders
- fix swapchain creation errors on GLES 2
- explicitly mark all shader resources as non-aliased
- correctly specify shader storage buffers as coherent for shaders that
  require them
- fix various memory barrier synchronization issues for opengl

v2.72.1

This release backports a number of bug fixes from master affecting the
v2.72.0 release, most notably extending the range of supported glslang
versions, as well as fixing the 3DLUT/ICC generation code.

Bug fixes:
- compatibility with glslang >= 8.13.3743
- compatibility with new glslang semantic versioning scheme
- fix broken shaders on some versions of GLES by defaulting to 32-bit
  precision for floating point math
- fix the vulkan API version passed to shaderc
- fix the extension check for glInvalidateTexImage
- fix pl_tex_create on older GLES versions
- fix OpenGL logging thread safety
- fix undefined memcmp() in pl_shader_av1_grain
- fix pl_render_target.repr being ignored by pl_render_image
- fix 3DLUT generation code (generated corrupt LUTs in all cases)
- fix symbol visibility on some versions of GCC
- fix potential overflow in BT.2390 shader
- properly restrict pl_shader_sample_polar to GLSL >= 130
- fix vulkan function loading of promoted core functions

Other changes:
- tiny performance gain in 3DLUT generation
- pl_opengl_create now logs GL_EXTENSIONS
- log some additional VkResult enum members
- improve several vulkan log messages by using friendly names of enums
- add a copy of the config.h variables to the libplacebo.pc file

v2.72.2

This hotfix release fixes an additional glslang linking/build issue that
was missed in v2.72.1.

Bug fixes:
- fix linking issue with some installations of glslang >= 11.0.0

v3.104.0

This is a major release, introducing many new features and
modifications. Most importantly, libplacebo now interoperates well with
FFmpeg's libav* abstractions. This is primarily exposed via a new set of
helpers, <libplacebo/utils/libav.h>, implemented as a single header
library. In addition to this, a number of other supporting changes have
been made to the API, most notably the unification of `pl_image` and
`pl_render_target` into a single `pl_frame` concept, similar in spirit
to AVFrame. As such, libplacebo now supports **rendering to planar
targets**, including subsampled YCbCr.

Besides the libav* compatibility changes, this release also brings with
it a new feature for custom shaders: buffer blocks, and persistent
storage. This can be used by third parties to implement stateful shaders
(e.g. motion interpolation or temporal deinterlacing), or be leveraged
to speed up some shaders by combining multiple passes into one.

Finally, various import/export procedures have been expanded, including
the ability to import host pointers and real-world DMABUFs.

Additions:
- add `pl_memory_qualifiers`, plus a corresponding `pl_shader_desc.memory`,
  to allow attaching GLSL memory qualifiers (coherent, volatile etc.) to
  shader descriptors
- add functions `pl_dispatch_save` and `pl_dispatch_load` to allow
  saving/restoring the contents of an entire `pl_dispatch`'s cache
- add functions `pl_renderer_save` and `pl_renderer_load` to allow
  saving/restoring the contents of an entire `pl_renderer`'s cache
- add `pl_vulkan_swapchain_params.prefer_hdr`, which will cause the
  surface format selection logic to try HDR output formats first
- add `pl_buf_copy` to copy from one buffer to another
- add `pl_get_detected_peak`, to read back the result of peak detection
- add `pl_primaries_superset` to test if one set of primaries is fully
  enclosed by another
- add `pl_color_map_params.gamut_clipping`, which will colorimetrically
  clip any out-of-gamut colors by desaturating them towards neutral gray
  until they're in-gamut, rather than clipping per channel as before
- add `PL_GPU_CAP_SUBGROUPS` and `pl_gpu_limits.subgroup_size`, to
  expose GLSL subgroup functionality via the `pl_gpu` interface
- add `pl_gpu_is_failed`, to query at a high level whether the `pl_gpu`
  is in some internal failure state. GPUs in this state should be
  recreated, using the appropriate mechanism
- add `pl_shader_custom`, to allow injecting arbitrary custom GLSL code
  into a `pl_shader`.
- add `pl_buf_params.import_handle` to allow importing buffers
- add `PL_HANDLE_HOST_POTR`, to allow importing arbitrary host pointers
- add `pl_pass_run_params.vertex_buf`, to allow drawing vertex data
  directly from a `pl_buf`, guarded by `pl_gpu_limits.max_vbo_size`
- add `_COUNT` members to all public enums, for consistency
- add `pl_shared_mem.drm_format_mod`, to allow communicating DRM format
  modifiers when importing/exporting textures
- add support for importing DMABUFs via EGL, via the new fields
  `pl_opengl_params.egl_display/context`
- add `pl_fmt.fourcc` to facilitate mapping between `pl_fmt` and DRM
- add the missing `pl_var_*` helpers, for consistency
- add `pl_plane_data_align` to help with aligning `pl_plane_data`
  structs to byte boundaries
- add support for STORAGE textures in user shaders, which can be used to
  persist data across separate invocations of the shader
- add support for BUFFER blocks in user shaders, which can be used to
  create UBOs or SSBOs for use inside shaders, the latter of which can
  also persist across frames and be used to store persistent state
- add PL_COLOR_PRIM_EBU_3213 and PL_COLOR_PRIM_FILM_C
- add a new header <libplacebo/utils/libav.h>, containing a variety of
  helper functions for interoperating between libav* and libplacebo
- add `demos/plplay.c` to serve as a demonstration of how to make a
  trivial playback loop with libavcodec and libplacebo
- add `pl_sample_src.component_mask` to allow sampling an arbitrary
  subset of the available components from a plane
- add `pl_frame_is_cropped` and `pl_frame_clear` to assist in properly
  clearing frames before rendering to them
- add `pl_tex_poll` to assist in interoperating with some external APIs
- add `pl_render_params.blend_params` to allow blending the final output

Changes:
- remove `pl_image.signature` and `pl_render_params.skip_redraw_caching`
- change vulkan surface format selection to prioritize formats by
  'score', preferring higher depth integer formats
- `pl_fmt` may now have PL_FMT_CAP_STORABLE even when `glsl_format` is
  NULL, in which case formatless image storage must be used
- `pl_buf_read` no longer requires `buf_offset` be a multiple of 4
- `pl_buf_*` commands are now synchronized internally:
- `pl_buf_write` and `pl_buf_read` now block while the buffer is in use
  Note: for this reason, `pl_buf_write` should not be used in loops
- `pl_tex_upload/download` may now be called on in-use buffers
- allow `pl_dispatch_compute` on shaders with outputs, including the
  ability to automatically determine the number of work groups based on
  the shader output resolution
- remove `pl_buf_params.type`, and the concept of buffer types in
  general. `pl_buf` is now a generic catch-all for any type of buffer,
  with individual capabilities in `pl_buf_params` determinig what type
  of shader operations it can be used for
- relax the alignment requirements on `pl_tex_transfer_params`
- change `pl_opengl_wrap_params` to allow directly importing
  framebuffers in addition to textures
- rename `pl_color_levels` members for clarity
- make `pl_opengl` ignore software rasterizers by default, unless the
  new field `pl_opengl_params.allow_software` is set
- add `pl_av1_grain_params.luma_comp` to allow drawing the luma
  component from a channel with nonzero index
- `pl_renderer` now supports rendering to planar targets, including
  subsampled targets
- `pl_image` and `pl_render_target` have been removed and unified into a
  single `pl_frame` concept
- remove `pl_tex_params.sample_mode/address_mode` and move them to
  `pl_desc_binding` instead, to decouple them from texture creation
- refactor the signature of `pl_tex_blit`

Fixes and performance improvements:
- fix an oversight where `pl_buf_destroy` delayed some buffer
  destructions unnecessarily
- fix a limitation where `pl_tex_destroy` sometimes delayed destroying
  textures unnecessarily
- improve the performance of `pl_dispatch`'s code for assembling UBOs
- improve the performance of `pl_shader_av1_grain` by switching from
  SSBOs to texture LUTs, also improving compatibility with older GL
- improve the performance of `pl_shader_detect_peak` on GPUs with access
  to subgroups operations
- fix an issue where reinitializing shader state objects with different
  settings sometimes resulted in undefined behaviour
- fix some GLSL backwards compatibility issues
- slightly cut down on unnecessary image layout transitions
- add some miscellaneous debug print-outs, and improve the legibility of
  some existing log messages
- fix an issue where freeing buffer variables from shader descriptors
  could result in use-after-free
- add support for vulkan memory imports requiring dedication allocations
- slightly improve, and fix, the vulkan memory placement logic
- significantly improve the performance of `pl_tex_download` by
  importing the target host pointer directly
- improve the performance of small LUTs, especially for the non-compute
  polar fallback path
- prevent `pl_renderer` from unneccessarily applying a 3DLUT when both
  the input and output frames have the same ICC profile
- fix the behaviour of partially specified `pl_bit_encoding` structs
- fix the component ordering on some odd packed vulkan formats
- fix an issue where `pl_plane_data_from_mask` broke for high bit depths
- make `pl_renderer` consult the dither bit depth from the texture
  precision, if absent from `pl_bit_encoding`
- fix the behaviour of `pl_renderer` when sampling from textures with
  swapped component orders
- fix the implementation of PL_COLOR_SYSTEM_BT_2100_HLG
- fix some issues relating to missing includes
- enforce legality of image usage parameters on `pl_vulkan_wrap`
- fix an undesired shader double-compilation when using orthogonal
  scalers with subsampled chroma planes
- fix an issue where application of a 3DLUT cleared the alpha channel
- add a missing extension to `pl_vulkan_recommended_extensions`
- fix the plane alignment code for oddly sized subsampled chroma
- fix the poor precision of `pl_shader_dither` for high bit depths
- fix several possible overflows in the BT.2390 shader
- fix a bug where using a polar sampler to draw a scaled overlay onto a
  non-storable target neglected to disable compute shaders
- fix a bug where the renderer could sometimes alias when downscaling,
  in particular if both the upsampler and downsampler are set to bicubic
- improve performance of scalers by avoiding bilinear filtering
- reduce verbosity of memory allocations
- fix missing PL_FMT_CAP_BLENDABLE on opengl fbos
- significantly improve precision of float literals in shaders
- add better error checking to gl_pass_create

v3.104.0-rc1

This is a major release, introducing many new features and
modifications. Most importantly, libplacebo now interoperates well with
FFmpeg's libav* abstractions. This is primarily exposed via a new set of
helpers, <libplacebo/utils/libav.h>, implemented as a single header
library. In addition to this, a number of other supporting changes have
been made to the API, most notably the unification of `pl_image` and
`pl_render_target` into a single `pl_frame` concept, similar in spirit
to AVFrame. As such, libplacebo now supports **rendering to planar
targets**, including subsampled YCbCr.

Besides the libav* compatibility changes, this release also brings with
it a new feature for custom shaders: buffer blocks, and persistent
storage. This can be used by third parties to implement stateful shaders
(e.g. motion interpolation or temporal deinterlacing), or be leveraged
to speed up some shaders by combining multiple passes into one.

Finally, various import/export procedures have been expanded, including
the ability to import host pointers and real-world DMABUFs.

Additions:
- add `pl_memory_qualifiers`, plus a corresponding `pl_shader_desc.memory`,
  to allow attaching GLSL memory qualifiers (coherent, volatile etc.) to
  shader descriptors
- add functions `pl_dispatch_save` and `pl_dispatch_load` to allow
  saving/restoring the contents of an entire `pl_dispatch`'s cache
- add functions `pl_renderer_save` and `pl_renderer_load` to allow
  saving/restoring the contents of an entire `pl_renderer`'s cache
- add `pl_vulkan_swapchain_params.prefer_hdr`, which will cause the
  surface format selection logic to try HDR output formats first
- add `pl_buf_copy` to copy from one buffer to another
- add `pl_get_detected_peak`, to read back the result of peak detection
- add `pl_primaries_superset` to test if one set of primaries is fully
  enclosed by another
- add `pl_color_map_params.gamut_clipping`, which will colorimetrically
  clip any out-of-gamut colors by desaturating them towards neutral gray
  until they're in-gamut, rather than clipping per channel as before
- add `PL_GPU_CAP_SUBGROUPS` and `pl_gpu_limits.subgroup_size`, to
  expose GLSL subgroup functionality via the `pl_gpu` interface
- add `pl_gpu_is_failed`, to query at a high level whether the `pl_gpu`
  is in some internal failure state. GPUs in this state should be
  recreated, using the appropriate mechanism
- add `pl_shader_custom`, to allow injecting arbitrary custom GLSL code
  into a `pl_shader`.
- add `pl_buf_params.import_handle` to allow importing buffers
- add `PL_HANDLE_HOST_POTR`, to allow importing arbitrary host pointers
- add `pl_pass_run_params.vertex_buf`, to allow drawing vertex data
  directly from a `pl_buf`, guarded by `pl_gpu_limits.max_vbo_size`
- add `_COUNT` members to all public enums, for consistency
- add `pl_shared_mem.drm_format_mod`, to allow communicating DRM format
  modifiers when importing/exporting textures
- add support for importing DMABUFs via EGL, via the new fields
  `pl_opengl_params.egl_display/context`
- add `pl_fmt.fourcc` to facilitate mapping between `pl_fmt` and DRM
- add the missing `pl_var_*` helpers, for consistency
- add `pl_plane_data_align` to help with aligning `pl_plane_data`
  structs to byte boundaries
- add support for STORAGE textures in user shaders, which can be used to
  persist data across separate invocations of the shader
- add support for BUFFER blocks in user shaders, which can be used to
  create UBOs or SSBOs for use inside shaders, the latter of which can
  also persist across frames and be used to store persistent state
- add PL_COLOR_PRIM_EBU_3213 and PL_COLOR_PRIM_FILM_C
- add a new header <libplacebo/utils/libav.h>, containing a variety of
  helper functions for interoperating between libav* and libplacebo
- add `demos/plplay.c` to serve as a demonstration of how to make a
  trivial playback loop with libavcodec and libplacebo
- add `pl_sample_src.component_mask` to allow sampling an arbitrary
  subset of the available components from a plane
- add `pl_frame_is_cropped` and `pl_frame_clear` to assist in properly
  clearing frames before rendering to them
- add `pl_tex_poll` to assist in interoperating with some external APIs
- add `pl_render_params.blend_params` to allow blending the final output

Changes:
- remove `pl_image.signature` and `pl_render_params.skip_redraw_caching`
- change vulkan surface format selection to prioritize formats by
  'score', preferring higher depth integer formats
- `pl_fmt` may now have PL_FMT_CAP_STORABLE even when `glsl_format` is
  NULL, in which case formatless image storage must be used
- `pl_buf_read` no longer requires `buf_offset` be a multiple of 4
- `pl_buf_*` commands are now synchronized internally:
- `pl_buf_write` and `pl_buf_read` now block while the buffer is in use
  Note: for this reason, `pl_buf_write` should not be used in loops
- `pl_tex_upload/download` may now be called on in-use buffers
- allow `pl_dispatch_compute` on shaders with outputs, including the
  ability to automatically determine the number of work groups based on
  the shader output resolution
- remove `pl_buf_params.type`, and the concept of buffer types in
  general. `pl_buf` is now a generic catch-all for any type of buffer,
  with individual capabilities in `pl_buf_params` determinig what type
  of shader operations it can be used for
- relax the alignment requirements on `pl_tex_transfer_params`
- change `pl_opengl_wrap_params` to allow directly importing
  framebuffers in addition to textures
- rename `pl_color_levels` members for clarity
- make `pl_opengl` ignore software rasterizers by default, unless the
  new field `pl_opengl_params.allow_software` is set
- add `pl_av1_grain_params.luma_comp` to allow drawing the luma
  component from a channel with nonzero index
- `pl_renderer` now supports rendering to planar targets, including
  subsampled targets
- `pl_image` and `pl_render_target` have been removed and unified into a
  single `pl_frame` concept
- remove `pl_tex_params.sample_mode/address_mode` and move them to
  `pl_desc_binding` instead, to decouple them from texture creation
- refactor the signature of `pl_tex_blit`

Fixes and performance improvements:
- fix an oversight where `pl_buf_destroy` delayed some buffer
  destructions unnecessarily
- fix a limitation where `pl_tex_destroy` sometimes delayed destroying
  textures unnecessarily
- improve the performance of `pl_dispatch`'s code for assembling UBOs
- improve the performance of `pl_shader_av1_grain` by switching from
  SSBOs to texture LUTs, also improving compatibility with older GL
- improve the performance of `pl_shader_detect_peak` on GPUs with access
  to subgroups operations
- fix an issue where reinitializing shader state objects with different
  settings sometimes resulted in undefined behaviour
- fix some GLSL backwards compatibility issues
- slightly cut down on unnecessary image layout transitions
- add some miscellaneous debug print-outs, and improve the legibility of
  some existing log messages
- fix an issue where freeing buffer variables from shader descriptors
  could result in use-after-free
- add support for vulkan memory imports requiring dedication allocations
- slightly improve, and fix, the vulkan memory placement logic
- significantly improve the performance of `pl_tex_download` by
  importing the target host pointer directly
- improve the performance of small LUTs, especially for the non-compute
  polar fallback path
- prevent `pl_renderer` from unneccessarily applying a 3DLUT when both
  the input and output frames have the same ICC profile
- fix the behaviour of partially specified `pl_bit_encoding` structs
- fix the component ordering on some odd packed vulkan formats
- fix an issue where `pl_plane_data_from_mask` broke for high bit depths
- make `pl_renderer` consult the dither bit depth from the texture
  precision, if absent from `pl_bit_encoding`
- fix the behaviour of `pl_renderer` when sampling from textures with
  swapped component orders
- fix the implementation of PL_COLOR_SYSTEM_BT_2100_HLG
- fix some issues relating to missing includes
- enforce legality of image usage parameters on `pl_vulkan_wrap`
- fix an undesired shader double-compilation when using orthogonal
  scalers with subsampled chroma planes
- fix an issue where application of a 3DLUT cleared the alpha channel
- add a missing extension to `pl_vulkan_recommended_extensions`
- fix the plane alignment code for oddly sized subsampled chroma
- fix the poor precision of `pl_shader_dither` for high bit depths
- fix several possible overflows in the BT.2390 shader
- fix a bug where using a polar sampler to draw a scaled overlay onto a
  non-storable target neglected to disable compute shaders
- fix a bug where the renderer could sometimes alias when downscaling,
  in particular if both the upsampler and downsampler are set to bicubic
- improve performance of scalers by avoiding bilinear filtering

v3.120.0

This is a feature release, introducing frame mixing, DRM format
modifiers, and support for custom LUTs -, while also greatly expanding
the available demo programs, in particular the `plplay` video player.

The main highlight is the new `pl_queue` abstraction living in
<libplacebo/utils/frame_queue.h>. This greatly simplifies the core of a
libplacebo-based video renderer by translating a stream of input frames
into an array of GPU-mapped textures suitable for frame mixing, given a
corresponding vsync timestamp. New frames can be delivered to this API
using a push or pull model, and they are lazily uploaded on an as-needed
basis as well as internally garbage collected when no longer needed.
This abstraction also contains all needed machinery for estimating
source/display framerates by comparing and averaging timestamps, freeing
users from the burden of having to accurately determine this information
a priori.

Also worth mentioning is the addition of support for custom LUTs,
currently only in Adobe's .cube format. They can be applied flexibly at
a number of locations in the video processing pipeline, including as a
replacement for YUV<->RGB conversion or tone/gamut mapping, and fed with
either normalized linear light or native-gamma values.

Among the included demo programs, the `plplay` example video player has
been greatly expanded - adding support for a settings GUI (based on
nuklear), frame timing and mixing, custom shaders, and more. This
example video player now serves as a convenient platform to demonstrate
all of libplacebo's advanced rendering features.

Finally, all of libplacebo now contains only code written entirely from
scratch (rather than deriving from mpv), opening up the possibility to
explore different licenses besides the current LGPLv2.1+. In particular,
permissive (MIT/BSD-style) licenses are being considered.

Additions:
- add asynchronous GPU callbacks, specifically to `pl_tex_transfer`,
  allowing for non-blocking host memory transfer operations
- add `pl_shared_mem.stride_w/h` to control dmabuf pitch
- add `pl_render_image_mix` to blend multiple frames into a single
  output image, given relative timestamp information
- add the `pl_filter_mitchell_clamp` filter preset
- add `pl_render_params.preserve_mixing_cache` to speed up redraws after
  renderer size changes when frame mixing is active
- add <libplacebo/utils/dav1d.h> to help with Dav1dPicture mapping
- implement `PL_HANDLE_HOST_PTR` for the OpenGL backend
- implement drm format modifiers for vulkan
- add a new field `pl_fmt.modifiers` for DRM format modifier negotiation
- add new header <libplacebo/shaders/lut.h> to load custom LUTs
  (currently only supporting the .cube format)
- add `index_data/buf` to `pl_pass_run_params`, adding support for
  indexed vertex data when dispatching shader passes
- add `pl_dispatch_vertex` to allow dispatching fragment shaders using
  a list of custom vertices with custom vertex attributes
- add `pl_frame_recreate_from_avframe` and `pl_download_avframe` to help
  downloading GPU textures back into AVFrame form
- add a new header <libplacebo/utils/frame_queue.h> to assist in taking
  a stream of (Frame, PTS) pairs as well as a list of VSync times and
  turning them into a stream of `pl_frame_mix` structs
- add `pl_white_from_temp` and `pl_color_adjustment.temperature` to
  apply white point adjustments between correlated color temperatures (K)
- add `pl_filter_preset.description` containing a longer, human-readable
  name for a given filter preset

Changes:
- `pl_3dlut_params` has been renamed `pl_icc_params`
- `pl_render_params.force_3dlut` has been renamed `force_icc_lut`
- `pl_3dlut_update/apply` have been renamed to `pl_icc_update/apply` and
  moved to a (conditionally installed) new header <libplacebo/shaders/icc.h>
- `pl_upload_plane` no longer initializes `out_plane->shift_x/y` to 0,
  instead leaving them unmodified (to avoid clobbering existing shift data)
- `pl_filter_box` has been renamed to `pl_filter_nearest`
- `pl_filter_triangle` has been renamed to `pl_filter_bilinear`
- `pl_render_params.frame_mixer = NULL` now disables frame mixing - to
  get back the old behaviour, set this to `&pl_oversample_frame_mixer`.
- `pl_color_map_params.gamut_warning` now highlights out-of-gamut colors
  in bright pink, rather than the old (ill-defined) inversion behaviour
- `pl_named_filter_config` has been renamed to `pl_filter_preset`
- `pl_find_named_filter` has been renamed to `pl_find_filter_preset`
- ditto for `pl_named_filter_function` and `pl_filter_function_preset`

Fixes and performance improvements:
- fix buffer overflow in custom shader STORAGE blocks
- fix include path for glslang >= 11.0.0
- actually enable shader subgroup operations for HDR peak detection
- fix locale dependence of shader parsing primitives
- fix AVCOL_SPC_SMPTE170M mapping
- fix wrong color space selection in `pl_vulkan_create_swapchain`
- work-around low UBO size limits on some platforms
- fix compilation issues on C++ due to the use of reserved identifiers
- fix `pl_get_detected_peak` on platforms without host-visible SSBOs
- fix edge case in vulkan texture handle capabilities check
- fix suboptimal mutex destruction code
- skip peak detection when outputting to HDR displays
- fix edge cases in shader LUT type selection logic
- avoid redundant scaling passes when scaling anamorphic content
- merge similar planes before dispatching heavy shaders (e.g.
  debanding, hooks)
- avoid scaling passes for certain small fractional scaling steps
- entirely avoid processing unneeded components when dispatching scalers
- avoid using more components than necessary for intermediate FBOs
- fix out-of-bounds read for small non-cropped emulated textures
- avoid thrashing the shader cache when reinitializing OpenGL FBOs
- fix incorrect include in <libplacebo/opengl.h>
- fix vk.xml priority issue on windows
- fix undefined behaviour / GPU hangs in HDR peak detection shader
- fix incorrect forwarding of DRM modifiers to the OpenGL backend
- fix crash on AV_PIX_FMT_FLAG_BAYER
- fix various compilation issues on certain platforms
- fix obscure edge-case in floating point printing routine
- `pl_render_params.force_icc_lut` now excludes no-op cases
- fix handling of custom shader COMPUTE blocks
- correctly apply hue and saturation controls for non-YCbCr color spaces

v3.120.1

This hotfix release fixes a number of minor issues with the v3.120.0
release, and also modularizes the included demo programs to cut down on
the number of compiled binaries.

Changes:
- hexadecimal strings in custom shaders may now include whitespace
- added 16-bit half float formats to the dummy pl_gpu
- significantly reduced verbosity of the included demo programs
- merged all of the demo program variants into a single binary that
  picks the best windowing system / graphical API at runtime
- install `plplay` when demos are enabled

Fixes and performance improvements:
- fixed an integer overflow in a texture bounds check
- fixed a false positive error in the test framework on 32-bit platforms
- fixed some minor issues with various outdated comments
- fixed a potential use-after-free in the `plplay` demo program when
  playing files containing embedded ICC profiles

v3.120.2

This minor release fixes a number of additional bugs related to the
thread queue, included demos, included helpers, and build system.

Changes:
- replace the `shaderc` library checks by pkg-config checks
- `pl_dispatch` no longer grows infinitely, but prunes stale cache
  entries after a certain threshold
- improve logging of GPU capabilities (including format capabilities)

Fixes and performance improvements:
- fix a typo on an error message
- fix a use-after-free edge case in `plplay`
- filter out Infinity, NaN and other values from fps/vps estimates
- add several warnings for suspected frame queue API misuses
- fix a crash when combining pl_render_image_mix with cropped frames
- fix a crash on AV_PIX_FMT_NONE in the libav helpers
- fix the loading of overlays in the `sdlimage` demo
- fix a number of potential overflows on 32-bit platforms
- omit redundant identity matrices in pl_shader_decode_color
- fix crash in frame queue with certain out-of-order PTS sequences
- add missing link to vulkan dependency in the `video-filtering` demo
- correctly shift overlays when drawing to subsampled YCbCr planes
- add missing check for PL_GPU_CAP_CALLBACKS in `utils/{libav,dav1d}.h`
- improve handling of asynchronous texture uploads in `utils/libav.h`

v3.120.3

This minor release fixes a number of regressions surrounding memory
imports and DRM modifiers, specifically aimed at issues that arose with
mpv's --hwdec=vaapi.

Changes:
- `pl_fmt.modifiers` now always includes DRM_FORMAT_MOD_INVALID on
   OpenGL, which instructs the implementation to not specify modifiers
- passing a DRM modifier not in the list of supported modifiers is now
  considered a hard error, to rule out non-working hwaccel formats

Fixes:
- fix a crash when using sampling shaders on textures with unknown formats
- fix improperly specified SDL header imports in the demos
- fix an issue where the vulkan texture handle capabilities were testing
  for presence of the wrong extension
- fix an issue where non-enabled DRM modifier structs were accidentally
  linked into the pNext chain, causing issues with some drivers

v4.157.0

This is a major new release involving a significant overhaul of the
public API, full thread safety, support for Direct3D 11 / Win32 /
MSVC, native HDR output, and more.

The primary way of accessing most libplacebo objects has been revamped.
Rather than writing e.g. `const struct pl_tex *image`, users now simply
write `pl_tex image`. In addition, the `struct pl_context *ctx` was
universally refactored and replaced by `pl_log log`, with no concern
besides logging.

Direct3D 11 is now natively supported by libplacebo, and compiling on
Windows in general has been made more straightforward.

The entire API was revamped to be thread safe by default, even when
using OpenGL (assuming the user provides the appropriate context binding
callbacks). Accompanying this change, the `pl_queue` has been rewritten
with multi-threaded decoding loops in mind. See the accompanying
`plplay` demo for an illustration.

Finally, this release brings with it a lot of features for feature
parity with mpv, such as the ability to get pass stats / timings,
oversample scaling, and more.

Additions:
- add a `void *user_data` field to `pl_frame`, with no further
  interpretation by libplacebo
- add `pl_queue_push_block`, useful for multi-threaded decoding loops
- add a `uint64_t timeout` to `pl_queue_update`, allowing it to
  block until frames are available even when not using a `get_frame`
  callback
- make `pl_queue_update` also return valid data when failing with
  PL_QUEUE_MORE, allowing access to partial/incomplete mix outputs
- allow calling `pl_render_image` on `image == NULL`, to render overlays
  only
- add `pl_get_buffer2`, API-compatible with AVCodecContext.get_buffer2
- add support for blitting from/to several obscure formats such as
  a1rgb5 or 64-bit integer formats
- add `pl_tex_clear_ex` to support clearing integer textures
- add `pl_render_params.ignore_icc_profiles`, for debugging
- add `pl_queue_params.interpolation_threshold`, to allow disabling
  frame mixing when the source FPS approximately matches the display FPS
- always accept DRM_FORMAT_MOD_INVALID for texture imports
- add extra windowing functions to <libplacebo/filters.h>
- add the `pl_fmt.gatherable` capability
- add `pl_shader_sample_oversample`, a variant of nearest-neighbour
  that preserves pixel aspect ratios - good for pixel art
- add `pl_scale_filters` alongside `pl_frame_mixers`
- add support for compile-time specialization constants (`pl_constant`),
  and use them to speed up recompilation of shaders with hard-coded
  constants
- add `pl_render_params.dynamic_constants`, which lifts hard-coded
  constants to dynamic variables - useful for scenarios in which render
  parameters are expected to change very frequently
- add more PL_COLOR_TRC_GAMMAxx definitions
- implement full black point adaptation, even when not using ICC
  profiles, and infer this black-point-adapted BT.1886 instead of gamma
  2.2 as the default gamma curve for SDR files.
- add `pl_shader_res.description` and `pl_shader_res.steps`, containing
  more friendly names for shaders plus a detailed list of operations
  that shader is performing
- add callbacks to `pl_dispatch` and `pl_renderer` for informing users
  of executed passes and their execution times
- add support for the Direct3D 11 graphics API
- add `pl_swapchain_colorspace_hint`, replacing
  `pl_swapchain_hdr_metadata` as the new way to update swapchain
  colorspace metadata at runtime. This can be used to e.g. switch
  between HDR and SDR mode, for supported swapchains
- add `pl_peak_detect_params.minimum_peak`, allowing users to constrain
  the detected peak values to only be sensible (e.g. above 1.0)

Changes:
- simplify the `shaderc` pkg-config check - rather than querying for
  `shaderc_shared.pc`, `shaderc_combined.pc` etc, simply check for
  `shaderc.pc`, matching upstream
- make almost everything thread-safe, and document the parts that
  aren't. In particular, almost all GPU state access is now thread safe,
  freeing up users to access `pl_gpu` instances from multiple threads,
  even when the underlying API is OpenGL
- deprecate `disable_overlay_sampling`, now effectively always true
- `struct pl_overlay` has been refactored completely to allow for
  overlays with more than one part per texture. The only way of using
  this struct is deprecated
- prefix `enum pl_queue_status` members by `PL_`, fixing an oversight in
  the previous version of this API
- make `pl_renderer` automatically clear the target image, freeing users
  from the responsibility of calling `pl_frame_clear` themselves. This
  can be controlled via three new fields in `pl_render_params`:
  `background_color`, `background_transparency` and `skip_target_clearing`
- rename `pl_context` to `pl_log`, and make its use optional. The old
  names have been deprecated. It now lives inside <libplacebo/log.h>
- add `typedefs` to all public-facing object types, o make them shorter
  to reference. For example, `const struct pl_tex *tex` is now simply
  `pl_tex tex`. This change affects almost every type of object in
  libplacebo. The old way of referencing these objects is still
  possible, but considered deprecated. Note that due to C++-specific
  reasons, C++ users *must* upgrade their codeto the new API style
- remove PL_PRIM_TRIANGLE_FAN
- remove support for 64-bit float formats, which probably don't work on
  any Vulkan implementation
- stop contrast-limiting ICC profiles, instead assuming perceptual
  profiles have infinite contrast
- remove `pl_shader_signature` for being necessarily unsafe
- require Vulkan 1.1 as the minimum vulkan version
- rename `pl_oversample_frame_mixer` to `pl_filter_oversample`, and
  allow using it for image scaling as well
- change `pl_color_space_monitor` from PL_COLOR_TRC_GAMMA22 to UNKNOWN
- change the signature of `pl_shader_(de)linearize` slightly
- significantly increase the default strengths of the desaturation
  settings in`pl_color_map_params`, to mimic the hollywood feel
- refactor `pl_glsl_desc` and `pl_gpu_caps` completely, in favor of the
  new structs `pl_glsl_version` and `pl_gpu_limits`, with new members.
  The old API is still available for the time being, but deprecated

Fixes and performance improvements:
- fix possible use-after-free in `plplay`
- don't explode `pl_queue` on NaN/Infinity/weird PTS values
- fix edge case involving plane merging for cropped images
- improve `plplay` by using threaded libplacebo APIs
- several fixes for edge cases in <libplacebo/utils/libav.h> helpers
- several fixes for 32-bit platforms (e.g. integer overflows)
- fix blending edge cases involving overlays and alpha channels
- skip some unnecessary matrix multiplications for RGB content
- allow for some small backwards PTS jumps in `pl_queue_update`
- fix drawing overlays to subsampled targets
- `pl_dispatch` now garbage collects old, unused passes to free up RAM
- various improvements to debug/diagnonstic printouts
- allow blitting from e.g. 2D to 3D textures
- slightly improve small texture transfers in some emulated edge cases
- fix several possible hash collisions for generated shaders, making the
  shader dispatch mechanism significantly more robust
- properly allow building against vulkan headers without linking to the
  vulkan loader
- C++ compatibility for public headers
- improve performance of textureGather-based polar sampling, especially
  for radius 2 and 4
- fix vulkan texture handle capabilities check, again
- don't include superfluous pNext chains, fixes undefined behavior
- fix crash on edge case when shader compilation fails
- infer unsampled alpha channels as 1.0, rather than 0.0
- properly infer `target->color` in `pl_render_image`
- properly tag the OpenGL swapchain as pl_color_space_monitor
- fix possible crash in pl_get_detected_peak
- fix several edge cases in pl_render_image_mix relating to LUTs,
  3DLUTs, HDR peak detection and so on
- fix sig_peak inferral for HLG content
- several compatibility fixes for older GLSL, and GLES 2.0
- fix possible use-after-free in pl_shader_custom
- fix `pl_color_map_params.gamut_clipping` for HDR targets
- reduce the number of redundant color space transformations required
  for frame mixing
- fix edge case in pl_dispatch_save for some ancient GL drivers
- several fixes for LLVM/MinGW/MSVC
- fix bug where pl_pass_run incorrectly invalidated/accessed
  `params->target` even for compute shaders
- add windows compatibility to several demo programs
- fix the pl_fmt <-> DRM fourcc format mapping table
- fix inappropriate texture access function for generated samplers with
  the sampler2D API
- avoid generating spurious EGL errors when probing for EGL format
  modifiers
- fix various typis in the documentation

v4.157.0-rc1

This is a major new release involving a significant overhaul of the
public API, full thread safety, support for Direct3D 11 / Win32 /
MSVC, native HDR output, and more.

The primary way of accessing most libplacebo objects has been revamped.
Rather than writing e.g. `const struct pl_tex *image`, users now simply
write `pl_tex image`. In addition, the `struct pl_context *ctx` was
universally refactored and replaced by `pl_log log`, with no concern
besides logging.

Direct3D 11 is now natively supported by libplacebo, and compiling on
Windows in general has been made more straightforward.

The entire API was revamped to be thread safe by default, even when
using OpenGL (assuming the user provides the appropriate context binding
callbacks). Accompanying this change, the `pl_queue` has been rewritten
with multi-threaded decoding loops in mind. See the accompanying
`plplay` demo for an illustration.

Finally, this release brings with it a lot of features for feature
parity with mpv, such as the ability to get pass stats / timings,
oversample scaling, and more.

Additions:
- add a `void *user_data` field to `pl_frame`, with no further
  interpretation by libplacebo
- add `pl_queue_push_block`, useful for multi-threaded decoding loops
- add a `uint64_t timeout` to `pl_queue_update`, allowing it to
  block until frames are available even when not using a `get_frame`
  callback
- make `pl_queue_update` also return valid data when failing with
  PL_QUEUE_MORE, allowing access to partial/incomplete mix outputs
- allow calling `pl_render_image` on `image == NULL`, to render overlays
  only
- add `pl_get_buffer2`, API-compatible with AVCodecContext.get_buffer2
- add support for blitting from/to several obscure formats such as
  a1rgb5 or 64-bit integer formats
- add `pl_tex_clear_ex` to support clearing integer textures
- add `pl_render_params.ignore_icc_profiles`, for debugging
- add `pl_queue_params.interpolation_threshold`, to allow disabling
  frame mixing when the source FPS approximately matches the display FPS
- always accept DRM_FORMAT_MOD_INVALID for texture imports
- add extra windowing functions to <libplacebo/filters.h>
- add the `pl_fmt.gatherable` capability
- add `pl_shader_sample_oversample`, a variant of nearest-neighbour
  that preserves pixel aspect ratios - good for pixel art
- add `pl_scale_filters` alongside `pl_frame_mixers`
- add support for compile-time specialization constants (`pl_constant`),
  and use them to speed up recompilation of shaders with hard-coded
  constants
- add `pl_render_params.dynamic_constants`, which lifts hard-coded
  constants to dynamic variables - useful for scenarios in which render
  parameters are expected to change very frequently
- add more PL_COLOR_TRC_GAMMAxx definitions
- implement full black point adaptation, even when not using ICC
  profiles, and infer this black-point-adapted BT.1886 instead of gamma
  2.2 as the default gamma curve for SDR files.
- add `pl_shader_res.description` and `pl_shader_res.steps`, containing
  more friendly names for shaders plus a detailed list of operations
  that shader is performing
- add callbacks to `pl_dispatch` and `pl_renderer` for informing users
  of executed passes and their execution times
- add support for the Direct3D 11 graphics API
- add `pl_swapchain_colorspace_hint`, replacing
  `pl_swapchain_hdr_metadata` as the new way to update swapchain
  colorspace metadata at runtime. This can be used to e.g. switch
  between HDR and SDR mode, for supported swapchains
- add `pl_peak_detect_params.minimum_peak`, allowing users to constrain
  the detected peak values to only be sensible (e.g. above 1.0)

Changes:
- simplify the `shaderc` pkg-config check - rather than querying for
  `shaderc_shared.pc`, `shaderc_combined.pc` etc, simply check for
  `shaderc.pc`, matching upstream
- make almost everything thread-safe, and document the parts that
  aren't. In particular, almost all GPU state access is now thread safe,
  freeing up users to access `pl_gpu` instances from multiple threads,
  even when the underlying API is OpenGL
- deprecate `disable_overlay_sampling`, now effectively always true
- `struct pl_overlay` has been refactored completely to allow for
  overlays with more than one part per texture. The only way of using
  this struct is deprecated
- prefix `enum pl_queue_status` members by `PL_`, fixing an oversight in
  the previous version of this API
- make `pl_renderer` automatically clear the target image, freeing users
  from the responsibility of calling `pl_frame_clear` themselves. This
  can be controlled via three new fields in `pl_render_params`:
  `background_color`, `background_transparency` and `skip_target_clearing`
- rename `pl_context` to `pl_log`, and make its use optional. The old
  names have been deprecated. It now lives inside <libplacebo/log.h>
- add `typedefs` to all public-facing object types, o make them shorter
  to reference. For example, `const struct pl_tex *tex` is now simply
  `pl_tex tex`. This change affects almost every type of object in
  libplacebo. The old way of referencing these objects is still
  possible, but considered deprecated. Note that due to C++-specific
  reasons, C++ users *must* upgrade their codeto the new API style
- remove PL_PRIM_TRIANGLE_FAN
- remove support for 64-bit float formats, which probably don't work on
  any Vulkan implementation
- stop contrast-limiting ICC profiles, instead assuming perceptual
  profiles have infinite contrast
- remove `pl_shader_signature` for being necessarily unsafe
- require Vulkan 1.1 as the minimum vulkan version
- rename `pl_oversample_frame_mixer` to `pl_filter_oversample`, and
  allow using it for image scaling as well
- change `pl_color_space_monitor` from PL_COLOR_TRC_GAMMA22 to UNKNOWN
- change the signature of `pl_shader_(de)linearize` slightly
- significantly increase the default strengths of the desaturation
  settings in`pl_color_map_params`, to mimic the hollywood feel
- refactor `pl_glsl_desc` and `pl_gpu_caps` completely, in favor of the
  new structs `pl_glsl_version` and `pl_gpu_limits`, with new members.
  The old API is still available for the time being, but deprecated

Fixes and performance improvements:
- fix possible use-after-free in `plplay`
- don't explode `pl_queue` on NaN/Infinity/weird PTS values
- fix edge case involving plane merging for cropped images
- improve `plplay` by using threaded libplacebo APIs
- several fixes for edge cases in <libplacebo/utils/libav.h> helpers
- several fixes for 32-bit platforms (e.g. integer overflows)
- fix blending edge cases involving overlays and alpha channels
- skip some unnecessary matrix multiplications for RGB content
- allow for some small backwards PTS jumps in `pl_queue_update`
- fix drawing overlays to subsampled targets
- `pl_dispatch` now garbage collects old, unused passes to free up RAM
- various improvements to debug/diagnonstic printouts
- allow blitting from e.g. 2D to 3D textures
- slightly improve small texture transfers in some emulated edge cases
- fix several possible hash collisions for generated shaders, making the
  shader dispatch mechanism significantly more robust
- properly allow building against vulkan headers without linking to the
  vulkan loader
- C++ compatibility for public headers
- improve performance of textureGather-based polar sampling, especially
  for radius 2 and 4
- fix vulkan texture handle capabilities check, again
- don't include superfluous pNext chains, fixes undefined behavior
- fix crash on edge case when shader compilation fails
- infer unsampled alpha channels as 1.0, rather than 0.0
- properly infer `target->color` in `pl_render_image`
- properly tag the OpenGL swapchain as pl_color_space_monitor
- fix possible crash in pl_get_detected_peak
- fix several edge cases in pl_render_image_mix relating to LUTs,
  3DLUTs, HDR peak detection and so on
- fix sig_peak inferral for HLG content
- several compatibility fixes for older GLSL, and GLES 2.0
- fix possible use-after-free in pl_shader_custom
- fix `pl_color_map_params.gamut_clipping` for HDR targets
- reduce the number of redundant color space transformations required
  for frame mixing
- fix edge case in pl_dispatch_save for some ancient GL drivers
- several fixes for LLVM/MinGW/MSVC
- fix bug where pl_pass_run incorrectly invalidated/accessed
  `params->target` even for compute shaders
- add windows compatibility to several demo programs
- fix the pl_fmt <-> DRM fourcc format mapping table

v4.192.0

This is a minor release, designed to synchronize with the release of
FFmpeg 5.0. It focuses mainly on improvements to color space handling -
including support for Dolby Vision Profile 5/8 content, completely
rewritten HDR tone/gamut mapping, and bringing `pl_color_space` more in
line with HDR10 metadata. Libplacebo now generally respects things like
mastering color space metadata, especially for PL_INTENT_SATURATION.
This technology is not yet perfect, and will be iterated upon in future
versions of libplacebo. This release serves mainly to lay the API
groundwork.

Other notable changes include support for H.274 film grain synthesis, as well
as improvements to the AVFrame<->libplacebo interop (in particular, support for
hardware accelerated frames), and various fixes related to alpha transparency.

As usual, also includes a number of bug fixes, performance improvements, and
miscellaneous improvements to the API and debug messages - such as the
inclusion of a brand-new Vulkan memory allocator, and a complete overhaul of
the Vulkan synchronization infrastructure to use timeline semaphores,
again for compatibility with FFmpeg Vulkan contexts.

Additions:
- add support for H.274 film grain synthesis
- add preprocessor macros for all params structs, allowing users to write e.g.
  `pl_render_params(.foo = bar)` to construct a `pl_render_params` pointer
  which implicitly includes any default fields, without the need for explicitly
  reading from pl_render_default_params
- add support for video/display rotation in the renderer
- add `pl_frame_copy_stream_props`
- add support for blending transparency against a checkerboard pattern
- add `pl_fmt.signature`, for render pass compatibility
- add `pl_pass_params.index_fmt` to allow 32-bit index buffers
- add `pl_dispatch_reset_frame`, to allow explicitly advancing the state
  of the PRNG and/or triggering garbage collection
- add the possibility of adding extra debug tags to GPU resources, which
  the default params helper macros set to the current source location
- add `pl_gpu_limits.max_variable_comps`, correctly specifying the upper
  bound on the number of uniform variable floats
- add `pl_vulkan_get`, `pl_opengl_get` and `pl_d3d11_get`
- add `pl_shader_set_alpha`
- add `pl_map_avframe_ex` and `pl_unmap_avframe`, which allow mapping extra
  AVFrame resources, and also support the use of hardware frames such as vaapi,
  dmabuf or vulkan
- add support for Dolby Vision color reshaping, via PL_COLOR_SYSTEM_DOLBYVISION
  and `pl_dovi_metadata` - including automatic mapping from AVFrames
- add <libplacebo/tone_mapping.h>, defining a collection of tone mapping
  primitives, and mechanisms for constructing LUTs, and including new
  functions such as BT.2446a and `spline`, as well as improvements to old
  curves such as `hable` and `linear` to make them more perceptually linear
- add a variety of new tone mapping modes (see `pl_tone_map_mode`), including
  auto-selection based on heuristics of the source characteristics
- add a variety of new gamut mapping modes (see `pl_gamut_mode`)
- add support for `NAME_gather` macros for use in user shaders

Changes:
- replace <libplacebo/shaders/av1.h> by the more general
  <libplacebo/shaders/film_grain.h>
- remove API members deprecated for libplacebo v3
- PL_ALPHA_UNKNOWN tagging on files is now assumed to be PL_ALPHA_INDEPENDENT,
  rather than PL_ALPHA_PREMULTIPLIED, and `pl_shader_decode_color` now also
  outputs independent alpha by default
- the `box` filter was removed entirely, due to a number of issues preventing
  it from being effectively useful in practice
- replace `pl_tex_transfer.stride_w/h` (specified in texels) by
  `row/depth_pitch` (specified in bytes)
- replace `pl_pass_params.target_dummy` by `target_format`, and
  requiring that rendered textures are compatible with this format
- allow calling `pl_queue_update` on NULL
- <libplacebo/vulkan.h> now requires support for the timeline semaphores
  feature, included automatically in Vulkan 1.2 and available via
  VK_KHR_timeline_semaphore in previous versions
- change pl_vulkan_hold/release API: removing VkAccessFlags, and replacing the
  VkSemaphore by pl_vulkan_sem (for timeline semaphore support)
- `pl_queue_push` may now be used to push frames out-of-order
- `pl_render_image_mix` may now be used on single frames, in which case
  libplacebo will still go through the mixer cache, potentially speeding up
  single-frame redraws (see: `pl_render_params.skip_caching_single_frames`)
- remove `pl_vulkan_params.disable_events`
- `pl_shared_mem.size` no longer needs to be set for DMABUFs and D3D11 textures
- remove support for 64-bit integer texture formats, since these are very
  poorly supported on most platforms and also extremely rarely needed
- completely refactor all of the tone mapping settings in `pl_color_map_params`,
  replacing the old `desaturation_*` and `tone_mapping_algo` by the new
  `tone_mapping_mode` and `tone_mapping_function`, and the old `gamut_warning`
  and `gamut_clipping` by the new `gamut_mode`
- completely refactor `pl_color_space`: deprecate the old `sig_peak`,
  `sig_scale` etc. fields in favor of merging `pl_hdr_metadata` into this
  struct, and update the API of several functions that previusly took
  `pl_color_space` struct values, to instead take pointers
- remove `pl_color_light` entirely, instead treating the OOTF as an inseparable
  part of the color transfer function (e.g. HLG)
- delete `pl_swapchain_colors` in favor of `pl_color_space` instead (which
  contains the exact same fields now)

Fixes and performance enhancements:
- improve the quality and performance of GPU random number generation
- fix int/float compilation error on GLES in dither shader
- correctly set minimum integer precision on GLES
- allow pl_recreate_plane to create non-host-readable FBOs
- correct GLSL version requirement for 3D LUT shader
- correctly check for presence of GL_EXT_texture_integer
- correctly check for presence of GL_EXT_texture_norm16 on GLES 3.0
- correctly check for presence of GL_EXT_color_buffer_float
- replace GL_ARB_debug_output by GL_KHR_debug
- fix GLSL shader version for GLES 2.0
- add support for GL_EXt_texture_rg on GLES
- use GL_ARRAY_BUFFER instead of GL_COPY_WRITE_BUFFER (GLES compatibility)
- correctly check for GL_UNPACK_IMAGE_HEIGHT presence
- disable host readback on too-old GLES
- add support for the `bgra8` image format on gl/gles and `bgrx8` on d3d11
- remove deprecated usage of bare pointers for OpenGL index data
- fix vulkan malloc efficiency estimate calculation
- fix a memory leak in the vulkan memory allocator for small (<1K) buffers
- complete rewrite of the vulkan memory allocator to improve throughput,
  reduce code complexity and generally reduce memory waste
- allow using libplacebo as a meson subproject
- fix cyclic header dependency
- fix dithering when the FBO bit depth is higher than the content bit depth
- fix segfault if command buffer allocation fails
- fix various thread safety issues in vulkan command polling
- properly invalidate framebuffers on OpenGL
- properly disable GL_DEPTH_TEST and GL_CULL_FACE when running GL passes
- fix GL_ARB_framebuffer_object check
- fix issue with rendering transparent images on non-transparent swapchains
- try and detect presence of alpha channels on opengl framebuffers
- fix OUTPUT and NATIVE_CROPPED hook expressions for flipped files
- fix EPOXY_HAS_EGL checks
- significance increase performance of ICC 3DLUT generation
- correctly set the C level to C11 during compilation
- properly align allocated memory to `max_align_t` (instead of `intmax_t`)
- fix `pl_cond_timedwait`
- fix bug where `pl_opengl_wrap`+`pl_tex_destroy` accidentally closed FD 0
- fix pl_get_buffer2 implementation
- fix alpha blending of transparent subtitles onto transparent images
- fix issue where frame blending could sometimes crash if the only image
  in the mix was too far away from the vsync
- fix segfault when dispatching compute shader output hook while frame blending
- fix UB when using the same shader with different types of textures on vulkan
- fix possible race condition when writing to the same vulkan resource twice
- fix issue where user shaders were sometimes executed as compute shaders
  despite no //!COMPUTE pragma
- properly align texel buffers on vulkan
- properly propagate HOOKED textures between passes of a shader
- also support importing vulkan features from meta-structs like
  `VkPhysicalDeviceVulkan12Features`
- drop the use of VkEvents entirely, and instead optimize the usage of pipeline
  barriers to always emit the minimum required dependency
- fix vulkan object type enum parsing on recent vulkan versions
- fix invalid output on the first frame after enabling peak detection
- fix linking order of glslang libraries
- fix generated .pc file on windows
- fix imports of dedicated memory with plane offsets into vulkan resources
- fix major performance issue when combining debanding with bilinear scaling
- fix issue where `pl_vulkan_wrap` did not support `pl_tex_params.user_data`
- fix compatibility with MoltenVK by adding VK_KHR_portability_subset
- various compatibility fixes for OpenGL version 2.1
- fix UB in `pl_test_pixfmt`
- fix issue where rendering to partial crops of vulkan textures untentionally
  invalidated the image contents outside of the rendering area
- reduce the rate of false negatives in the renderer mixing cache
- fix strided OpenGL texture uploads
- fix crash in the frame mixer when the image color space changes mid-stream
- fix check for EGL DMA buffer modifiers
- fix division by zero in tone mapping shader
- make `pl_mpv_user_shader_destroy` properly reset the passed pointer
- fix undefined behavior passing negative values to `pl_shader_decode_color`
- fix bug where PL_QUEUE_MORE resulted in invalid frame mix outputs
- fix thread race between `pl_queue_push` and reading from a `pl_frame_mix`
- fix `pl_render_high_quality_params`
- fix parsing .cube LUTs with scientific notation floats
- inline LUTs into shader text less aggressively
- disable peak detection in `pl_render_default_params`, instead moving it to
  `pl_render_high_quality_params`
- fix edge case where HDR spaces didn't properly disable linearization
- fix various issues involving the allocation of per-pass identifiers on d3d11
- fix issue where the d3d11 swapchain unnecessarily held on to the framebuffer
- make `pl_swapchain_start/stop_frame` more robust against threading issues or
  API misuse
- fix the application of `pl_color_adjustment.gamma` in `pl_shader_decode_color`
- add support for `pl_pass_params.cached_program` on d3d11

v4.192.0-rc1

This is a minor release that focuses mainly on improvements to color space
handling - including support for Dolby Vision Profile 5/8 content, completely
rewritten HDR tone/gamut mapping, and bringing `pl_color_space` more in line
with HDR10 metadata. Libplaceb now generally respects things like mastering
color space metadata, especially for PL_INTENT_SATURATION. This technology is
not yet perfect, and will be iterated upon in future versions of libplacebo.
This release serves mainly to lay the API groundwork.

Other notable changes include support for H.274 film grain synthesis, as well
as improvements to the AVFrame<->libplacebo interop (in particular, support for
hardware accelerated frames), and various fixes related to alpha transparency.

As usual, also includes a number of bug fixes, performance improvements, and
miscellaneous improvements to the API and debug messages - such as the
inclusion of a brand-new Vulkan memory allocator, and a complete overhaul of
the Vulkan synchronization infrastructure to use timeline semaphores.

Additions:
- add support for H.274 film grain synthesis
- add preprocessor macros for all params structs, allowing users to write e.g.
  `pl_render_params(.foo = bar)` to construct a `pl_render_params` pointer
  which implicitly includes any default fields, without the need for explicitly
  reading from pl_render_default_params
- add support for video/display rotation in the renderer
- add `pl_frame_copy_stream_props`
- add support for blending transparency against a checkerboard pattern
- add `pl_fmt.signature`, for render pass compatibility
- add `pl_pass_params.index_fmt` to allow 32-bit index buffers
- add `pl_dispatch_reset_frame`, to allow explicitly advancing the state
  of the PRNG and/or triggering garbage collection
- add the possibility of adding extra debug tags to GPU resources, which
  the default params helper macros set to the current source location
- add `pl_gpu_limits.max_variable_comps`, correctly specifying the upper
  bound on the number of uniform variable floats
- add `pl_vulkan_get`, `pl_opengl_get` and `pl_d3d11_get`
- add `pl_shader_set_alpha`
- add `pl_map_avframe_ex` and `pl_unmap_avframe`, which allow mapping extra
  AVFrame resources, and also support the use of hardware frames such as vaapi,
  dmabuf or vulkan
- add support for Dolby Vision color reshaping, via PL_COLOR_SYSTEM_DOLBYVISION
  and `pl_dovi_metadata` - including automatic mapping from AVFrames
- add <libplacebo/tone_mapping.h>, defining a collection of tone mapping
  primitives, and mechanisms for constructing LUTs, and including new
  functions such as BT.2446a and `spline`, as well as improvements to old
  curves such as `hable` and `linear` to make them more perceptually linear
- add a variety of new tone mapping modes (see `pl_tone_map_mode`), including
  auto-selection based on heuristics of the source characteristics
- add a variety of new gamut mapping modes (see `pl_gamut_mode`)
- add support for `NAME_gather` macros for use in user shaders

Changes:
- replace <libplacebo/shaders/av1.h> by the more general
  <libplacebo/shaders/film_grain.h>
- remove API members deprecated for libplacebo v3
- PL_ALPHA_UNKNOWN tagging on files is now assumed to be PL_ALPHA_INDEPENDENT,
  rather than PL_ALPHA_PREMULTIPLIED, and `pl_shader_decode_color` now also
  outputs independent alpha by default
- the `box` filter was removed entirely, due to a number of issues preventing
  it from being effectively useful in practice
- replace `pl_tex_transfer.stride_w/h` (specified in texels) by
  `row/depth_pitch` (specified in bytes)
- replace `pl_pass_params.target_dummy` by `target_format`, and
  requiring that rendered textures are compatible with this format
- allow calling `pl_queue_update` on NULL
- <libplacebo/vulkan.h> now requires support for the timeline semaphores
  feature, included automatically in Vulkan 1.2 and available via
  VK_KHR_timeline_semaphore in previous versions
- change pl_vulkan_hold/release API: removing VkAccessFlags, and replacing the
  VkSemaphore by pl_vulkan_sem (for timeline semaphore support)
- `pl_queue_push` may now be used to push frames out-of-order
- `pl_render_image_mix` may now be used on single frames, in which case
  libplacebo will still go through the mixer cache, potentially speeding up
  single-frame redraws (see: `pl_render_params.skip_caching_single_frames`)
- remove `pl_vulkan_params.disable_events`
- `pl_shared_mem.size` no longer needs to be set for DMABUFs and D3D11 textures
- remove support for 64-bit integer texture formats, since these are very
  poorly supported on most platforms and also extremely rarely needed
- completely refactor all of the tone mapping settings in `pl_color_map_params`,
  replacing the old `desaturation_*` and `tone_mapping_algo` by the new
  `tone_mapping_mode` and `tone_mapping_function`, and the old `gamut_warning`
  and `gamut_clipping` by the new `gamut_mode`
- completely refactor `pl_color_space`: deprecate the old `sig_peak`,
  `sig_scale` etc. fields in favor of merging `pl_hdr_metadata` into this
  struct, and update the API of several functions that previusly took
  `pl_color_space` struct values, to instead take pointers
- remove `pl_color_light` entirely, instead treating the OOTF as an inseparable
  part of the color transfer function (e.g. HLG)
- delete `pl_swapchain_colors` in favor of `pl_color_space` instead (which
  contains the exact same fields now)

Fixes and performance enhancements:
- improve the quality and performance of GPU random number generation
- fix int/float compilation error on GLES in dither shader
- correctly set minimum integer precision on GLES
- allow pl_recreate_plane to create non-host-readable FBOs
- correct GLSL version requirement for 3D LUT shader
- correctly check for presence of GL_EXT_texture_integer
- correctly check for presence of GL_EXT_texture_norm16 on GLES 3.0
- correctly check for presence of GL_EXT_color_buffer_float
- replace GL_ARB_debug_output by GL_KHR_debug
- fix GLSL shader version for GLES 2.0
- add support for GL_EXt_texture_rg on GLES
- use GL_ARRAY_BUFFER instead of GL_COPY_WRITE_BUFFER (GLES compatibility)
- correctly check for GL_UNPACK_IMAGE_HEIGHT presence
- disable host readback on too-old GLES
- add support for the `bgra8` image format on gl/gles and `bgrx8` on d3d11
- remove deprecated usage of bare pointers for OpenGL index data
- fix vulkan malloc efficiency estimate calculation
- fix a memory leak in the vulkan memory allocator for small (<1K) buffers
- complete rewrite of the vulkan memory allocator to improve throughput,
  reduce code complexity and generally reduce memory waste
- allow using libplacebo as a meson subproject
- fix cyclic header dependency
- fix dithering when the FBO bit depth is higher than the content bit depth
- fix segfault if command buffer allocation fails
- fix various thread safety issues in vulkan command polling
- properly invalidate framebuffers on OpenGL
- properly disable GL_DEPTH_TEST and GL_CULL_FACE when running GL passes
- fix GL_ARB_framebuffer_object check
- fix issue with rendering transparent images on non-transparent swapchains
- try and detect presence of alpha channels on opengl framebuffers
- fix OUTPUT and NATIVE_CROPPED hook expressions for flipped files
- fix EPOXY_HAS_EGL checks
- significance increase performance of ICC 3DLUT generation
- correctly set the C level to C11 during compilation
- properly align allocated memory to `max_align_t` (instead of `intmax_t`)
- fix `pl_cond_timedwait`
- fix bug where `pl_opengl_wrap`+`pl_tex_destroy` accidentally closed FD 0
- fix pl_get_buffer2 implementation
- fix alpha blending of transparent subtitles onto transparent images
- fix issue where frame blending could sometimes crash if the only image
  in the mix was too far away from the vsync
- fix segfault when dispatching compute shader output hook while frame blending
- fix UB when using the same shader with different types of textures on vulkan
- fix possible race condition when writing to the same vulkan resource twice
- fix issue where user shaders were sometimes executed as compute shaders
  despite no //!COMPUTE pragma
- properly align texel buffers on vulkan
- properly propagate HOOKED textures between passes of a shader
- also support importing vulkan features from meta-structs like
  `VkPhysicalDeviceVulkan12Features`
- drop the use of VkEvents entirely, and instead optimize the usage of pipeline
  barriers to always emit the minimum required dependency
- fix vulkan object type enum parsing on recent vulkan versions
- fix invalid output on the first frame after enabling peak detection
- fix linking order of glslang libraries
- fix generated .pc file on windows
- fix imports of dedicated memory with plane offsets into vulkan resources
- fix major performance issue when combining debanding with bilinear scaling
- fix issue where `pl_vulkan_wrap` did not support `pl_tex_params.user_data`
- fix compatibility with MoltenVK by adding VK_KHR_portability_subset
- various compatibility fixes for OpenGL version 2.1
- fix UB in `pl_test_pixfmt`
- fix issue where rendering to partial crops of vulkan textures untentionally
  invalidated the image contents outside of the rendering area
- reduce the rate of false negatives in the renderer mixing cache
- fix strided OpenGL texture uploads
- fix crash in the frame mixer when the image color space changes mid-stream
- fix check for EGL DMA buffer modifiers
- fix division by zero in tone mapping shader
- make `pl_mpv_user_shader_destroy` properly reset the passed pointer
- fix undefined behavior passing negative values to `pl_shader_decode_color`
- fix bug where PL_QUEUE_MORE resulted in invalid frame mix outputs
- fix thread race between `pl_queue_push` and reading from a `pl_frame_mix`
- fix `pl_render_high_quality_params`
- fix parsing .cube LUTs with scientific notation floats
- inline LUTs into shader text less aggressively
- disable peak detection in `pl_render_default_params`, instead moving it to
  `pl_render_high_quality_params`
- fix edge case where HDR spaces didn't properly disable linearization
- fix various issues involving the allocation of per-pass identifiers on d3d11
- fix issue where the d3d11 swapchain unnecessarily held on to the framebuffer
- make `pl_swapchain_start/stop_frame` more robust against threading issues or
  API misuse
- fix the application of `pl_color_adjustment.gamma` in `pl_shader_decode_color`
- add support for `pl_pass_params.cached_program` on d3d11

v4.192.1

This is a minor bugfix release, containing some crucial follow-up for
v4.192.0, most notably a fix for a regression in the YCbCr decoding
logic that resulted in slightly green-shifted output on 10/12-bit files.

Fixes and performance enhancements:
- fix a regression causing incorrect YCbCr decoding for 10-bit content
- fix overzealous error detection on OpenGL initialization
- fix build issue caused by the use of 64-bit atomics on some platforms
- fix a regression in renderer functionality caused by an unintended
  restriction of FBO requirements on certain platforms (older d3d11)
- fix an issue where certain d3d11 texture formats were not blittable
- fix debug layer checks on d3d 11.0
- fix context creation on older d3d11 runtimes
- fix an issue where PL_TONE_MAP_HYBRID unintentionally oversaturated
  low brightness scenes
- fix a build issue on certain BSD platforms
- update nuklear to 4.9.5, fixing some build-time warnings
- fix an issue where a change to the d3d11 swapchain code resulted in
  lots of unnecessary log spam
- fix an issue where some d3d11 formats were detected as gatherable, but
  not sampleable

v4.208.0

This major release brings with it a number of fixes and changes for
compatibility with both upstream and downstream projects, native HDR
output on D3D11, and a complete redesign of the way ICC profiles are
handled.

Additions:
- add helper macros linearize() and delinearize(), expanding to the
  definition of the gamma function in use for the video signal
- add various new helper functions relating to colorspaces and
  primaries, see the API change log for a more comprehensive list
- add `pl_render_params.force_low_bit_depth_fbos` for
  debugging/performance tweaking purposes
- add `pl_plane.flipped`, to allow representing individual flipped
  frames in a way that semantically decouples from the presentation rect
  (e.g. for OpenGL framebuffers, or planes with negative stride)
- add '%' and '=' as operators to custom shaders, matching mpv
- add `pl_vulkan.(un)lock_queue` for interop with other libraries
- add `pl_frame.acquire/release` for better interop with hardware
  decoders. These are only called on an as-needed basis immediately
  before and after a frame is actually used for rendering, with only one
  frame being acquired at any given time
- add `pl_film_grain_from_av` helper function
- add support for configuring the swapchain color space on D3D11, using
  the existing pl_swapchain_colorspace_hint mechanism
- add an entirely new ICC profile shader API, allowing ICC profiles to
  be persistently opened (pl_icc_open) and their metadata exposed,
  with explicit `pl_icc_decode` and `pl_icc_encode` operations instead
  of a single monolithic decode+apply step
- add `pl_render_params.plane_up/downscaler`, allowing to override the
  upscaler/downscaler for subsampled chroma planes in particular
- add `pl_filter_function/config.name` for debugging/logging purposes

Changes:
- pl_log_create is no longer an exported symbol, instead becoming
  versioned by the compiled API version. `pl_log_create` is now a macro
  expanding to the name of this versioned function
- `pl_overlay_part` has been refactored, adding the new field `coords`
  to control the coordinate system relative to which the part is placed
  on-screen, as well as being generalized to support floating point
  positions
- deprecate PL_HOOK_PRE_OVERLAY, as a result of overlays no longer being
  applied during the rendering pipeline
- default `pl_color_map_params.gamut_mode` to PL_GAMUT_CLIP, replacing
  PL_GAMUT_DARKEN
- DRM modifiers are now required for vulkan dmabuf interop
- `pl_vulkan.queue_*` are now *always* set to valid queues for that
  operation type, even if it means including duplicates
- `pl_render_image` with NULL image now reports itself as a blend pass
  (blending 0 frames) instead of a frame pass to the info callbacks
- completely refactor/remove the old ICC/3DLUT shader API
  (`pl_icc_update`, `pl_icc_apply` etc.)
- <libplacebo/shaders/icc.h> is now installed unconditionally, with
  `pl_icc_open` simply failing when built without lcms2
- versions of glslang before the new versioning scheme (10.x.x) are no
  longer supported

Fixes and performance enhancements:
- fix pl_tone_map_reinhard.param_min to prevent division by zero
- fix left-over asserts preventing misaligned buffer uploads via
  pl_upload_plane
- fix bug where emulated rgb textures had alpha incorrectly
  preinitialized to 0 instead of 1
- overlays are now always rendered onto the final blended image, solving
  various bugs and unexpected edge cases due to image overlays being
  blended in the middle of the rendering pipeline
- fix a bug where tone-mapping without a state object resulted in broken
  behavior
- allow `pl_shader_sample_polar` to work with external samplers or
  flipped textures without incurring a performance penalty
- fix the behavior of pl_shader_sample_oversample, which was previously
  producing very wrong results
- fix an issue where the dither depth was incorrectly picked in a number
  of edge cases
- fix a number of issues with the H.274 film grain shader
- fix a bug where grayscale images were slightly too green
- fix a bug where `pl_vulkan.queue_transfer` was never set
- fix possible UB in pl_opengl_wrap_tex on some drivers with broken
  texture channel depth queries
- fix issue where some shader LUTs were being regenerated on every
  single frame rather than properly cached
- fix shader compilation error on older GLSL
- fix bug where images were sometimes undesiredly being scaled in linear
  light
- fix SDR<->SDR tone-mapping to properly be a no-op (linear stretch)
- fix use-after-free in pl_get_buffer2's error path
- fix d3d11 build issues on older versions of the SDK
- fix edge case where auto-detected vulkan in the absence of
  glslang/shaderc caused the build to fail
- fix build issues with up-to-date vulkan SDK
- fix issue where non-coherent buffer imports were used in ways not
  adhering to the non-coherent memory atom size
- fix various issues and undefined behavior when flushing mapped
  buffers, especially for non-coherent memory
- avoid some validation warnings about improper pipeline barriers
- fix runtime error with up-to-date MoltenVK
- fix issue where some pl_frame_mix structs resulted no frames being
  mixed, triggering an assertion
- fix bug where overlays were drawn flipped onto flipped planes when
  rendering a NULL image
- fix allocation alignment issues on some platforms (notably win32 i686)
- fix compatibility issues with older macOS
- fix error handling in pl_cond_timedwait
- fix build issues with older vulkan versions
- fix build issue of demos/sdlimage in some configurations
- reduce VRAM consumption of ICC 3DLUTs by 50%

v4.208.0-rc1

This major release brings with it a number of fixes and changes for
compatibility with both upstream and downstream projects, native HDR
output on D3D11, and a complete redesign of the way ICC profiles are
handled.

Additions:
- add helper macros linearize() and delinearize(), expanding to the
  definition of the gamma function in use for the video signal
- add various new helper functions relating to colorspaces and
  primaries, see the API change log for a more comprehensive list
- add `pl_render_params.force_low_bit_depth_fbos` for
  debugging/performance tweaking purposes
- add `pl_plane.flipped`, to allow representing individual flipped
  frames in a way that semantically decouples from the presentation rect
  (e.g. for OpenGL framebuffers, or planes with negative stride)
- add '%' and '=' as operators to custom shaders, matching mpv
- add `pl_vulkan.(un)lock_queue` for interop with other libraries
- add `pl_frame.acquire/release` for better interop with hardware
  decoders. These are only called on an as-needed basis immediately
  before and after a frame is actually used for rendering, with only one
  frame being acquired at any given time
- add `pl_film_grain_from_av` helper function
- add support for configuring the swapchain color space on D3D11, using
  the existing pl_swapchain_colorspace_hint mechanism
- add an entirely new ICC profile shader API, allowing ICC profiles to
  be persistently opened (pl_icc_open) and their metadata exposed,
  with explicit `pl_icc_decode` and `pl_icc_encode` operations instead
  of a single monolithic decode+apply step
- add `pl_render_params.plane_up/downscaler`, allowing to override the
  upscaler/downscaler for subsampled chroma planes in particular
- ad `pl_filter_function/config.name` for debugging/logging purposes

Changes:
- pl_log_create is no longer an exported symbol, instead becoming
  versioned by the compiled API version. `pl_log_create` is now a macro
  expanding to the name of this versioned function
- `pl_overlay_part` has been refactored, adding the new field `coords`
  to control the coordinate system relative to which the part is placed
  on-screen, as well as being generalized to support floating point
  positions
- deprecate PL_HOOK_PRE_OVERLAY, as a result of overlays no longer being
  applied during the rendering pipeline
- default `pl_color_map_params.gamut_mode` to PL_GAMUT_CLIP, replacing
  PL_GAMUT_DARKEN
- DRM modifiers are now required for vulkan dmabuf interop
- `pl_vulkan.queue_*` are now *always* set to valid queues for that
  operation type, even if it means including duplicates
- `pl_render_image` with NULL image now reports itself as a blend pass
  (blending 0 frames) instead of a frame pass to the info callbacks
- completely refactor/remove the old ICC/3DLUT shader API
  (`pl_icc_update`, `pl_icc_apply` etc.)
- <libplacebo/shaders/icc.h> is now installed unconditionally, with
  `pl_icc_open` simply failing when built without lcms2

Fixes and performance enhancements:
- fix pl_tone_map_reinhard.param_min to prevent division by zero
- fix left-over asserts preventing misaligned buffer uploads via
  pl_upload_plane
- fix bug where emulated rgb textures had alpha incorrectly
  preinitialized to 0 instead of 1
- overlays are now always rendered onto the final blended image, solving
  various bugs and unexpected edge cases due to image overlays being
  blended in the middle of the rendering pipeline
- fix a bug where tone-mapping without a state object resulted in broken
  behavior
- allow `pl_shader_sample_polar` to work with external samplers or
  flipped textures without incurring a performance penalty
- fix the behavior of pl_shader_sample_oversample, which was previously
  producing very wrong results
- fix an issue where the dither depth was incorrectly picked in a number
  of edge cases
- fix a number of issues with the H.274 film grain shader
- fix a bug where grayscale images were slightly too green
- fix a bug where `pl_vulkan.queue_transfer` was never set
- fix possible UB in pl_opengl_wrap_tex on some drivers with broken
  texture channel depth queries
- fix issue where some shader LUTs were being regenerated on every
  single frame rather than properly cached
- fix shader compilation error on older GLSL
- fix bug where images were sometimes undesiredly being scaled in linear
  light
- fix SDR<->SDR tone-mapping to properly be a no-op (linear stretch)
- fix use-after-free in pl_get_buffer2's error path
- fix d3d11 build issues on older versions of the SDK
- fix edge case where auto-detected vulkan in the absence of
  glslang/shaderc caused the build to fail
- fix build issues with up-to-date vulkan SDK
- fix issue where non-coherent buffer imports were used in ways not
  adhering to the non-coherent memory atom size
- fix various issues and undefined behavior when flushing mapped
  buffers, especially for non-coherent memory
- avoid some validation warnings about improper pipeline barriers
- fix runtime error with up-to-date MoltenVK
- fix issue where some pl_frame_mix structs resulted no frames being
  mixed, triggering an assertion
- fix bug where overlays were drawn flipped onto flipped planes when
  rendering a NULL image

v4.208.0-rc2

This major release brings with it a number of fixes and changes for
compatibility with both upstream and downstream projects, native HDR
output on D3D11, and a complete redesign of the way ICC profiles are
handled.

Additions:
- add helper macros linearize() and delinearize(), expanding to the
  definition of the gamma function in use for the video signal
- add various new helper functions relating to colorspaces and
  primaries, see the API change log for a more comprehensive list
- add `pl_render_params.force_low_bit_depth_fbos` for
  debugging/performance tweaking purposes
- add `pl_plane.flipped`, to allow representing individual flipped
  frames in a way that semantically decouples from the presentation rect
  (e.g. for OpenGL framebuffers, or planes with negative stride)
- add '%' and '=' as operators to custom shaders, matching mpv
- add `pl_vulkan.(un)lock_queue` for interop with other libraries
- add `pl_frame.acquire/release` for better interop with hardware
  decoders. These are only called on an as-needed basis immediately
  before and after a frame is actually used for rendering, with only one
  frame being acquired at any given time
- add `pl_film_grain_from_av` helper function
- add support for configuring the swapchain color space on D3D11, using
  the existing pl_swapchain_colorspace_hint mechanism
- add an entirely new ICC profile shader API, allowing ICC profiles to
  be persistently opened (pl_icc_open) and their metadata exposed,
  with explicit `pl_icc_decode` and `pl_icc_encode` operations instead
  of a single monolithic decode+apply step
- add `pl_render_params.plane_up/downscaler`, allowing to override the
  upscaler/downscaler for subsampled chroma planes in particular
- add `pl_filter_function/config.name` for debugging/logging purposes

Changes:
- pl_log_create is no longer an exported symbol, instead becoming
  versioned by the compiled API version. `pl_log_create` is now a macro
  expanding to the name of this versioned function
- `pl_overlay_part` has been refactored, adding the new field `coords`
  to control the coordinate system relative to which the part is placed
  on-screen, as well as being generalized to support floating point
  positions
- deprecate PL_HOOK_PRE_OVERLAY, as a result of overlays no longer being
  applied during the rendering pipeline
- default `pl_color_map_params.gamut_mode` to PL_GAMUT_CLIP, replacing
  PL_GAMUT_DARKEN
- DRM modifiers are now required for vulkan dmabuf interop
- `pl_vulkan.queue_*` are now *always* set to valid queues for that
  operation type, even if it means including duplicates
- `pl_render_image` with NULL image now reports itself as a blend pass
  (blending 0 frames) instead of a frame pass to the info callbacks
- completely refactor/remove the old ICC/3DLUT shader API
  (`pl_icc_update`, `pl_icc_apply` etc.)
- <libplacebo/shaders/icc.h> is now installed unconditionally, with
  `pl_icc_open` simply failing when built without lcms2
- versions of glslang before the new versioning scheme (10.x.x) are no
  longer supported

Fixes and performance enhancements:
- fix pl_tone_map_reinhard.param_min to prevent division by zero
- fix left-over asserts preventing misaligned buffer uploads via
  pl_upload_plane
- fix bug where emulated rgb textures had alpha incorrectly
  preinitialized to 0 instead of 1
- overlays are now always rendered onto the final blended image, solving
  various bugs and unexpected edge cases due to image overlays being
  blended in the middle of the rendering pipeline
- fix a bug where tone-mapping without a state object resulted in broken
  behavior
- allow `pl_shader_sample_polar` to work with external samplers or
  flipped textures without incurring a performance penalty
- fix the behavior of pl_shader_sample_oversample, which was previously
  producing very wrong results
- fix an issue where the dither depth was incorrectly picked in a number
  of edge cases
- fix a number of issues with the H.274 film grain shader
- fix a bug where grayscale images were slightly too green
- fix a bug where `pl_vulkan.queue_transfer` was never set
- fix possible UB in pl_opengl_wrap_tex on some drivers with broken
  texture channel depth queries
- fix issue where some shader LUTs were being regenerated on every
  single frame rather than properly cached
- fix shader compilation error on older GLSL
- fix bug where images were sometimes undesiredly being scaled in linear
  light
- fix SDR<->SDR tone-mapping to properly be a no-op (linear stretch)
- fix use-after-free in pl_get_buffer2's error path
- fix d3d11 build issues on older versions of the SDK
- fix edge case where auto-detected vulkan in the absence of
  glslang/shaderc caused the build to fail
- fix build issues with up-to-date vulkan SDK
- fix issue where non-coherent buffer imports were used in ways not
  adhering to the non-coherent memory atom size
- fix various issues and undefined behavior when flushing mapped
  buffers, especially for non-coherent memory
- avoid some validation warnings about improper pipeline barriers
- fix runtime error with up-to-date MoltenVK
- fix issue where some pl_frame_mix structs resulted no frames being
  mixed, triggering an assertion
- fix bug where overlays were drawn flipped onto flipped planes when
  rendering a NULL image
- fix allocation alignment issues on some platforms (notably win32 i686)
- fix compatibility issues with older macOS
- fix error handling in pl_cond_timedwait
- fix build issues with older vulkan versions
- fix build issue of demos/sdlimage in some configurations

v5.228.0-rc1

This is a major release, bumping up the major version to v5 and dropping
all APIs deprecated in v3.x. The other major breaking change of this
release is a switch away from the external `libepoxy` OpenGL dependency
in favor of the (optionally bundled) `glad` version 2. This is now
included, along with various other build-time dependencies, as git
submodules. Users are advised to clone with `git clone --recursive` in
order to satisfy these dependencies automatically, while distros
maintainers are nonetheless encouraged to continue packaging them.

In addition, this release brings with it a number of new features and
changes - including support for fully automatic GPU deinterlacing, error
diffusion dithering, gamma-aware dithering, and a number of improvements
to the handling of HDR sources and output displays, as well as several
notable bug fixes and performance enhancements.

Additions:
- add `pl_gpu_limits.array_size_constants` to indicate whether or not
  push constants can be used to size arrays
- add PL_HANDLE_MTL_TEX, PL_HANDLE_IOSURFACE and `pl_shared_mem.plane`
  to improve interop with MoltenVK
- add the informational fields `pl_opengl.major, `pl_opengl.minor`,
  `pl_opengl_extensions` and the `pl_opengl_has_ext` utility function
- add `pl_opengl_params.get_proc_addr` and `get_proc_addr_ex`
- add `pl_deband_params.grain_neutral`, the effect of which is to scale
  down / disable adding noise near this value
- add <libplacebo/shaders/deinterlacing.h>, containing a basic
  implementation of yadif, bob and weave
- add support for deinterlacing metadata to `pl_render_params`,
  `pl_frame`, and `pl_source_frame`
- add <libplacebo/shaders/dithering.h>, splitting this off from its
  previous location inside <libplacebo/shaders/colorspace.h>
- add `pl_shader_error_diffusion` and related helper functions, as well
  as `pl_render_params.error_diffusion`
- add `pl_dither_params.transfer` to support gamma-aware dithering
- add `pl_icc_params.force_bpc` to help work around black point
  compensation issues on "broken" v4 and v2 profiles

Changes:
- fields and functions deprecated in libplacebo v3 have been removed
- `python3-mako` is now bundled as a submodule to make resolving this
  dependency easier
- drop `libepoxy` as a dependency, and require `glad` v2 instead, the
  latter of which is added as a submodule to make building easier
- drop the `PL_STRUCT` transitional macro, and switch to a consistent
  API where e.g. `pl_tex` is a typedef of `const struct pl_tex_t *`.
- `PL_LUT_CONVERSION` now explicitly overrides ICC profiles as well
- HDR color spaces no longer default to having a black point of 0.005
  nits, instead now defaulting to "true" black (1e-7 nits)
- BT.1886 sources are now automatically tuned to match the swapchain /
  detected target contrast, rather than defaulting to 1000:1
- move `pl_queue_params.frame_duration` to `pl_source_frame.duration`
- the `vulkan-link` and `opengl-loader` boolean meson options have been
  removed in favor of the `vk-proc-addr` and `gl-proc-addr` feature
  flags, defaulting to `auto` instead of `yes`
- a copy of `vulkan.h` and `vk.xml` have been bundled as submodules to
  make satisfying these dependencies easier
- `<libplacebo/opengl.h>`, `<libplacebo/vulkan.h>` and
  `<libplacebo/d3d11.h`> are now installed unconditonally, with stubs
  for `pl_vulkan_create` etc. available even if these features are
  disabled at compile time
- `pl_render_info.index` no longer indicates the number of frames being
  mixed on PL_RENDER_STAGE_BLEND, instead being relegated to the new
  field `pl_render_info.count`

Fixes and performance enhancements:
- fix a bug where shaders with dynamically sized arrays would fail to
  compile on MoltenVK
- reduce the frequency at which polar compute shaders need to be
  recompiled
- fix compilation issues with MSVC
- fix an issue where vulkan portability extensions were not correctly
  detected
- fix a possible deadlock when using a multi-threaded opengl context
- specify the correct calling convention for EGL debug callbacks
- fix a bug where PL_INTENT_ABSOLUTE_COLORIMETRIC broke ICC profiles
- improve the handling of perceptual ICC profiles, especially on
  "broken" v4 or v2 profiles
- fix undefined behavior on 32-bit vulkan systems
- fix bugs in the vulkan swapchain recreation
- fix an issue where HDR metadata was not correctly reflected back to
  the renderer on vulkan swapchains
- fix a bug where d3d11 swapchains failed being created on older
  versions of windows where high-bit-depth swapchains are unavailable
- fix a bug where HDR metadata sent to the swapchain was not correctly
  inferred to valid values
- `pl_shader_deband` has been rewritten to slightly improve performance,
  especially when the texture has more channels than necessary
- `pl_shader_deband` no longer raises the black point due to clipping
- fix build issues on GCC < 6
- improve validity of partially set `pl_color_space` structs
- fix `pl_find_tone_map_function` not having an implementation
- fix a bug where cubic spline frame mixing did not work in `plplay`
- fix a memory leak in `pl_queue_destroy`
- fix a bug where changing `pl_icc_params.max_luma` or `intent` did not
  correctly invalidate the ICC 3DLUT and renderer cache
- greatly improve the performance and accuracy of 3DLUTs (ICC, .cube)
- fix compilation on newer glslang and make this code forward-compatible
- fix an issue where `pl_shader_dither` raised the apparent brightness
  of the image when dithering to low bit depths
- fix compilation on vulkan systems with `vulkan.h` available but no
  vulkan loader
- fix an issue where DV metadata requiring an EL was partially applied
- fix an issue where PQ HDR sources were incorrectly assumed to have a
  black point scaled to the mastering display, rather than absolute zero
- fix an issue where disabling `async_compute` led to undefined behavior
  on systems with async compute queues available
- fix an issue where debanding was applied *after* user shaders, causing
  massive performance/quality loss in the case of user shaders that
  upscaled the input planes somehow - in exchange for a slight
  performance penalty when rendering a heavily cropped source image with
  debanding enabled
- fix an issue where plane shaders were sometimes not correctly merged
  with the following image combination shader
- fix an issue where inverse tone mapping did not work with
  `pl_tone_map_auto`
- fix a massive performance regression in the non-compute fallback polar
  shader, especially on nvidia and apple systems - in exchange for a
  slight performance penalty on AMD systems
- slightly boost the performance of shader LUTs in some very specific
  circumstances
- fix an issue where nonlinear shader LUTs did not work on GLSL < 130