[FFmpeg-devel] [PATCH] skip ##ix chunks reading as video/audio data

[Michael Niedermayer]

On Sun, Nov 23, 2008 at 04:04:25PM +0200, Maksym Veremeyenko wrote:
> Hi!
>
> I was investigating an errors happens during transcoding huge DV avi files. 
> The error messages from DV decoder:
> [...]
> AC EOB marker is absent pos=91
> AC EOB marker is absent pos=64
> AC EOB marker is absent pos=67
> AC EOB marker is absent pos=64
> [...]
> show that frame is broken. After locating that frame i found it contains a 
> part of avi index table instead of DV data. Attached screenshot show that 
> avi file used a ##ix chunk for pointing to further index. ffmpeg reads that 
> chunk (00ix #14100) as frame data....
>
> Same problem happens also to https://trac.videolan.org/vlc/ticket/964
>
> Skipping ##ix chunk was done in the same manner as it was done for ix## 
> chunks. The minor changes i removed
> n < s->nb_streams
> condition, because n is 100 in all cases it found 00ix:
>
> FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF 30 
> 2146511652 805240575 100
> FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF 30 30 2146511653 
> 808451839 100
> FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF 30 30 69 2146511654 1764765695 
> 100
> FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF 30 30 69 78 2146511655 2020159536 100
> FFFFFFFF FFFFFFFF FFFFFFFF 30 30 69 78 30 2146511656 813197616 100
> FFFFFFFF FFFFFFFF 30 30 69 78 30 FA 2146511657 -97486743 0
> FFFFFFFF 30 30 69 78 30 FA 1 2146511658 33173624 100
> 30 30 69 78 30 FA 1 0 2146511659 129584 100
>                                         ^^^
>
> or 01ix :
>
> FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF 30 
> 2146641244 805240575 100
> FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF 30 31 2146641245 
> 825229055 100
> FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF 30 31 69 2146641246 1764831231 
> 100
> FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF 30 31 69 78 2146641247 2020159792 100
> FFFFFFFF FFFFFFFF FFFFFFFF 30 31 69 78 38 2146641248 947415345 100
> FFFFFFFF FFFFFFFF 30 31 69 78 38 FA 2146641249 -96962455 1
> FFFFFFFF 30 31 69 78 38 FA 1 2146641250 33175672 100
> 30 31 69 78 38 FA 1 0 2146641251 129592 100
>                                         ^^^

what are these numbers supposed to be?


>
> Is this patch OK?

NO, this is just wrong you are removing the stream validity check thus
litterally breaking the demuxer.

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

The greatest way to live with honor in this world is to be what we pretend
to be. -- Socrates
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