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lavc/vvc: Mark SPS used if multiple CLVSSs use it

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Consider the following sequence of NALUs (with some PPSs etc. omitted
for brevity):
1. SPS (ID=0, content=A)
2. IDR (SPS=0)
3. IDR (SPS=0)
4. SPS (ID=0, content=B)
5. TRAIL (SPS=0)

When decode_sps is called for NALU 3., ps->sps_id_used is cleared as
IDRs are one way of forming a CLVSS.  Then, old_sps is non-NULL
containing the result of calling decode_sps for NALU 2.  We haven't
received any SPSs between NALUs 2. and 3., therefore old_sps and rsps
are identical and the function returns.  The issue is that, at this
point, ps->sps_id_used is still zero despite the SPS being used for IDR
3.  This results in the check for conflicting SPSs not working properly
when decode_sps is called for NALU 5., allowing prediction between
pictures with different SPSs and probably all sorts of other
shenanigans.

Patch addresses the problem outlined above by also setting
ps->sps_id_used in the early return case.
This commit is contained in:
Frank Plowman
2025-07-29 21:42:26 +01:00
committed by James Almer
parent 2e19e74a29
commit f82748d5e0
1 changed files with 3 additions and 2 deletions
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5
libavcodec/vvc/ps.c
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@ -288,9 +288,10 @@ static int decode_sps(VVCParamSets *ps, AVCodecContext *c, const H266RawSPS *rsp
} }
if (old_sps) { if (old_sps) {
if (old_sps->r == rsps || !memcmp(old_sps->r, rsps, sizeof(*old_sps->r))) if (old_sps->r == rsps || !memcmp(old_sps->r, rsps, sizeof(*old_sps->r))) {
ps->sps_id_used |= (1 << sps_id);
return 0; return 0;
else if (ps->sps_id_used & (1 << sps_id)) } else if (ps->sps_id_used & (1 << sps_id))
return AVERROR_INVALIDDATA; return AVERROR_INVALIDDATA;
} }