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avcodec/h2645_vui: interpret a degenerate SAR as unspecified

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Per ITU-T H.264 (ISO/IEC 14496-10) Annex E.2.1 and ITU-T H.265
(ISO/IEC 23008-2) Annex E.3.1, when sar_width or sar_height is zero
the sample aspect ratio shall be considered unspecified. Internally
ffmpeg represents an unspecified SAR as 0/1, while fractions with a
zero denominator are not handled properly (den=0 is silently changed
to den=1 in h264_ps.c, turning an invalid 20480/0 into a "valid" but
impossibly extreme 20480/1); so we bridge the gap by replacing x/0
with 0/1 at the VUI parsing layer.

An av_log warning is added so an invalid SAR in the bitstream is
diagnosed rather than silently overwritten.

This fixes a problem with some video files provided by game
OddBallers when executed with Wine/Proton, which report SAR 20480/0.

Based on patch by Giovanni Mascellani <gmascellani@codeweavers.com>.
Fixes: ticket #23321

Signed-off-by: Jun Zhao <barryjzhao@tencent.com>
This commit is contained in:
Jun Zhao
2026-06-07 18:55:16 +00:00
committed by James Almer
co-authored by James Almer
parent bb49197ede
commit e598463b3d
1 changed files with 6 additions and 0 deletions
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libavcodec/h2645_vui.c
+6
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@@ -46,6 +46,12 @@ void ff_h2645_decode_common_vui_params(GetBitContext *gb, H2645VUI *vui, void *l
else if (vui->aspect_ratio_idc == EXTENDED_SAR) {
vui->sar.num = get_bits(gb, 16);
vui->sar.den = get_bits(gb, 16);
if (!vui->sar.num || !vui->sar.den) {
av_log(logctx, AV_LOG_WARNING,
"Invalid SAR %d/%d in bitstream, treating as unspecified.\n",
vui->sar.num, vui->sar.den);
vui->sar = (AVRational){ 0, 1 };
}
} else
av_log(logctx, AV_LOG_WARNING,
"Unknown SAR index: %u.\n", vui->aspect_ratio_idc);