[FFmpeg-devel] [PATCH v2] lavf: vvc_probe: enforce SPS -> PPS -> IRAP detection order to fix invalid stream detection

[FFmpeg-devel] [PATCH v2] 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>

[v2] lavf: vvc_probe: fix based on review feedback

Changes since v1:
- Added a flag to force sps, pps, iraq to appear in order;
- Modified score where pps, iraq appeared in the wrong position;
- Set a smaller score for incomplete sps, pps, iraq to deal with situations that may look like vvc format

Signed-off-by: xiongweixiao <xiongweixiaoxxw@gmail.com>
---
 libavformat/vvcdec.c | 19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

diff --git a/libavformat/vvcdec.c b/libavformat/vvcdec.c
index 0a0e24b71c..1d7be17258 100644
--- a/libavformat/vvcdec.c
+++ b/libavformat/vvcdec.c
@@ -44,6 +44,7 @@ static int vvc_probe(const AVProbeData *p)
 {
     uint32_t code = -1;
     int sps = 0, pps = 0, irap = 0;
+    int valid_pps = 0, valid_irap = 0;
     int i;
 
     for (i = 0; i < p->buf_size - 1; i++) {
@@ -60,17 +61,29 @@ 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:
+                pps++;
+                if (sps) 
+                    valid_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:
+                irap++;
+                if (valid_pps) 
+                    valid_irap++;
+                break;
             }
         }
     }
 
-    if (sps && pps && irap)
+    if (valid_irap) 
         return AVPROBE_SCORE_EXTENSION + 1; // 1 more than .mpg
+    if (sps && pps && irap)     
+        return AVPROBE_SCORE_EXTENSION / 2; 
+    if (sps || pps || irap) 
+        return AVPROBE_SCORE_EXTENSION / 4;
     return 0;
 }
 
-- 
2.34.1

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Re: [FFmpeg-devel] [PATCH v2] lavf: vvc_probe: enforce SPS -> PPS -> IRAP detection order to fix invalid stream detection

[Michael Niedermayer]

[-- Attachment #1.1: Type: text/plain, Size: 2341 bytes --]

Hi xiongweixiao

On Sun, May 11, 2025 at 11:43:08PM +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
> 
> Signed-off-by: xiongweixiao <xiongweixiaoxxw@gmail.com>
> 
> [v2] lavf: vvc_probe: fix based on review feedback
> 
> Changes since v1:
> - Added a flag to force sps, pps, iraq to appear in order;
> - Modified score where pps, iraq appeared in the wrong position;
> - Set a smaller score for incomplete sps, pps, iraq to deal with situations that may look like vvc format
> 

The commit message no longer matches the patch


> Signed-off-by: xiongweixiao <xiongweixiaoxxw@gmail.com>
> ---
>  libavformat/vvcdec.c | 19 ++++++++++++++++---
>  1 file changed, 16 insertions(+), 3 deletions(-)
> 
> diff --git a/libavformat/vvcdec.c b/libavformat/vvcdec.c
> index 0a0e24b71c..1d7be17258 100644
> --- a/libavformat/vvcdec.c
> +++ b/libavformat/vvcdec.c
> @@ -44,6 +44,7 @@ static int vvc_probe(const AVProbeData *p)
>  {
>      uint32_t code = -1;
>      int sps = 0, pps = 0, irap = 0;
> +    int valid_pps = 0, valid_irap = 0;
>      int i;
>  
>      for (i = 0; i < p->buf_size - 1; i++) {
> @@ -60,17 +61,29 @@ 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:
> +                pps++;
> +                if (sps) 

Trailing whitspace isnt allowed in our git


thx

[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Elect your leaders based on what they did after the last election, not
based on what they say before an election.


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