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Audio output plugins can use this to expedite discarding pending
buffers. This reduces latency upon seeking or stopping the input.

This new callback also supports explicit draining, but this is not
used for the time being.

This should cleanup locking when applying the volume, though there are
still some (non-crashing) races in setting/getting the volume.

This also adds an API to report the volume from the output, though it's
currently left as a dummy.

This prepares for a possible cleanup of the audio output object,
especially hiding more stuff into the core.

Maximum buffering time (AOUT_MAX_PREPARE_TIME) is increased to 2
seconds, consistent with increases in audio hardware buffer sizes.
In practice however, this is bound to the input PTS delay.

Maximum advance time is updated accordingly (+ 1 second).

Lip desynchronization tolerance is segregated, following EBU R37:
 - 40 ms (as before) maximum audio advance
 - 60 ms maximum audio delay.

Also move some stuff from vlc_config.h to vlc_aout*.h

With only one input per output, the lock is only useful:
 - to restart the audio instance (needed 3 out of 4 locks anyway),
 - to propagate volume change to the mixer or output plugin,
 - to access the FIFO from the output plugin thread (if applicable).

So 4 fine-grained was over-engineering. Most importantly, the locking
scheme was overly complicated and generally misunderstood/misused. Also
to avoid lock inversion, some unlocking/relocking sequences were
introduced; they broke atomicity.

We could certainly reduce the scope of the remaining lock. Since we
have one only input per output, most of the code is only ever run from
the decoder thread. Thus reentrancy is not anymore needed in some
places. But first aout_Restart() needs to be fixed and simplified.

This is required for PulseAudio synchronization and to pause/resume
with low-latency. This should also be useful for other buffered
 audio outputs such as ALSA or CoreAudio.

This should help Doxygen parse VLC headers, and generally makes headers
easier to read. LibVLC already uses a similar approach.

This improves mute flag handling in the PulseAudio output:
We do not blindly reset the mute flag.

Only two call sites checked for errors. Anyway, the implementation does
not check for errors.

This was only used to change the OSS or ALSA device on the fly.
However, this really should be done with a variable callback, not from
the configuration.

Signed-off-by: Rémi Denis-Courmont <remi@remlab.net>

Signed-off-by: Rémi Denis-Courmont <remi@remlab.net>

audio filter plugins are now useless.
This breaks visual (needs to be ported to filter_t) and will likely
expose bugs in under-used audio filter2 infrastructure.

TODO: use filter chain instead of custom filter handling in core.

This migrates to a filter_t-like syntax

(Yeah, some automatic variables were renamed too)

aout_buffer_t now looks very much like a subset of block_t at the
source code level. By the way, we might want to revisit the return value
of date_Increment()...