[FFmpeg-devel] [PATCH] lavf: vvc_probe: enforce SPS -> PPS -> IRAP detection order to fix invalid stream detection

[FFmpeg-devel] [PATCH] lavf: vvc_probe: enforce SPS -> PPS -> IRAP detection order to fix invalid stream detection

[xiongweixiao]

The current vvc_probe function checks for SPS, PPS, and IRAP NAL units but does not enforce their detection order. This can lead to false positives when PPS or IRAP appear before SPS, causing malformed or non-compliant bitstreams to be incorrectly identified as valid VVC streams.

This patch modifies the logic to use boolean flags and enforces the correct detection sequence: SPS must be detected before PPS, and PPS before IRAP. This ensures more accurate probing and prevents invalid bitstreams from being misidentified.

This change addresses issues reported in:
- https://trac.ffmpeg.org/ticket/11496
- https://trac.ffmpeg.org/ticket/11087

Signed-off-by: xiongweixiao <xiongweixiaoxxw@gmail.com>
---
 libavformat/vvcdec.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/libavformat/vvcdec.c b/libavformat/vvcdec.c
index 0a0e24b71c..573b352f41 100644
--- a/libavformat/vvcdec.c
+++ b/libavformat/vvcdec.c
@@ -60,11 +60,11 @@ static int vvc_probe(const AVProbeData *p)
 
             switch (type) {
             case VVC_SPS_NUT:       sps++;  break;
-            case VVC_PPS_NUT:       pps++;  break;
+            case VVC_PPS_NUT:       if (sps) pps++;  break;
             case VVC_IDR_N_LP:
             case VVC_IDR_W_RADL:
             case VVC_CRA_NUT:
-            case VVC_GDR_NUT:       irap++; break;
+            case VVC_GDR_NUT:       if (pps) irap++; break;
             }
         }
     }
-- 
2.34.1

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Re: [FFmpeg-devel] [PATCH] lavf: vvc_probe: enforce SPS -> PPS -> IRAP detection order to fix invalid stream detection

[Michael Niedermayer]

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Hi xiongweixiao

On Sun, May 11, 2025 at 01:08:14PM +0800, xiongweixiao wrote:
> The current vvc_probe function checks for SPS, PPS, and IRAP NAL units but does not enforce their detection order. This can lead to false positives when PPS or IRAP appear before SPS, causing malformed or non-compliant bitstreams to be incorrectly identified as valid VVC streams.
> 
> This patch modifies the logic to use boolean flags and enforces the correct detection sequence: SPS must be detected before PPS, and PPS before IRAP. This ensures more accurate probing and prevents invalid bitstreams from being misidentified.
> 
> This change addresses issues reported in:
> - https://trac.ffmpeg.org/ticket/11496
> - https://trac.ffmpeg.org/ticket/11087

I suggest to return a lower score when pps / irap occur in the wrong
location. And the current score if they ever occur in the correct
location
This way mp3 will be detected fine but also somewhat malformed
VVC can still be detected

thx

[...]
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Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Opposition brings concord. Out of discord comes the fairest harmony.
-- Heraclitus

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