Spec fixes for Argon bitstreams
- Sep 15, 2022
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David Conrad authored
Section 7.9.2 returns 0 "If RefMiRows[ srcIdx ] is not equal to MiRows, RefMiCols[ srcIdx ] is not equal to MiCols" dav1d was comparing pixel width/height, not block width/height, so conform with the spec
d4a2b75d -
David Conrad authored
Individual OBMC lapped predictions have a max width of 64 pixels for the top lap and have a max height of 64 for the left laps This is 7.11.3.9. Overlapped motion compensation process step4 = Clip3( 2, 16, Num_4x4_Blocks_Wide[ candSz ] ) dav1d wasn't clipping this as needed, which means that with scaled MC, the interpolation of the 2nd half of a 128 block was incorrect, since mx/my for subpel filter selection need to be reset at the 64 pixel boundary
eb25f00c -
David Conrad authored
This is the parameter combination: num_y_points == 0 && num_cb_points == 0 && num_cr_points == 0 && chroma_scaling_from_luma == 1 && clip_to_restricted_range == 1 Film grain application has two effects: adding noise, and optionally clipping to video range For luma, the spec skips film grain application if there's no noise (num_y_points == 0), but for chroma, it's only skipped if there's no chroma noise *and* chroma_scaling_from_luma is false This means it's possible for there to be no noise (num_*_points = 0), but if clip_to_restricted_range is true then chroma pixels can be clipped to video range, if chroma_scaling_from_luma is true. Luma pixels, however, aren't clipped to video range unless there's noise to apply. dav1d currently skips applying film grain entirely if there is no noise, regardless of the secondary clipping.
10f5ce54 -
David Conrad authored
The syntax of itu_t_t35_payload_bytes is not defined in the AV1 specification, but it does state that decoders should ignore the entire OBU if they do not understand it.
673ee248 -
David Conrad authored
In section 5.11.34 txSz is always defined to TX_4X4 if Lossless is true Chroma deblock filter size calculation needs to use this overridden txSz when lossless is enabled
2152826b -
David Conrad authored
The spec divides err by two, rounding to 0, instead of >>1, which rounds towards negative infinity
e202fa08 -
David Conrad authored
It's possible to encode a large coefficient that becomes 0 after the clipping in dequant (Abs( dq ) & 0xFFFFFF), e.g. 0x1000000 After that &0xFFFFFF, coeffs are saturated in the range of [-(1 << (bitdepth+7)), 1 << (bitdepth+7)) dav1d implements this saturation via umin(dq - sign, cf_max), then applies the sign afterwards via xor. However, for dq = 0 and sign = 1, this step evaulates to umin(UINT_MAX, cf_max) == cf_max instead of the expected 0. So instead, do unsigned saturate as umin(dq, cf_max + sign), then apply sign via (sign ? -dq : dq) On arm this is the same number of instructions, since cneg exists and is used On x86 this requires an additional instruction, but this isn't a latency-critical path
ee98592b -
David Conrad authored
In 8-bit adst, it's possible that the final Round2(x[0], 12) can exceed 16-bits signed Specifically, in 7.13.2.6. Inverse ADST4 process, the precision requirement is: "It is a requirement of bitstream conformance that all values stored in the s and x arrays by this process are representable by a signed integer using r + 12 bits of precision." For 8 bits, r is 16 for both row and column, so x[] can be 28-bit signed. For values [134215680, 134217727] (within 2047 of the maximum 28-bit value), the final Round2(x[0], 12) evaluates to 32768, exceeding 16-bits signed. So switch to using sqrshrn, which saturates to 16-bits signed This is a continuation of: Commit b53ff29d arm: itx: Do clipping in all narrowing downshifts
1bdb776c
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