Frank Plowman f82748d5e0 lavc/vvc: Mark SPS used if multiple CLVSSs use it ...

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.

2025-08-02 15:04:39 +00:00

50 KiB

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