[FFmpeg-devel] [PATCH] libavformat/avc.c annexb parsing corrupts packets

[Baptiste Coudurier]

Hi Michael,

On 08/13/2009 05:00 PM, Michael Niedermayer wrote:
> 4On Mon, Jul 27, 2009 at 05:10:33PM +0200, matteo.elli at m-elli.it wrote:
>> Hi,
>>
>> code in libavformat/avc.c is seldom executed but it surely does when you transmux (vcodec=copy) from h264 in a ts container to h264 in an mp4/mov/mkv/avi container.
>>
>> The code there fails to handle annexb 00 00 01 NAL three byets prefixes properly and cuts the last byte in the previous NAL corrupting the whole frame.
>>
>> Here is my proposed fix.
>>
>> Index: libavformat/avc.c
>> ===================================================================
>> --- libavformat/avc.c	(revision 19515)
>> +++ libavformat/avc.c	(working copy)
>> @@ -39,15 +39,15 @@
>>           if( (x - 0x01010101)&  (~x)&  0x80808080 ) { // generic
>>               if( p[1] == 0 ) {
>>                   if( p[0] == 0&&  p[2] == 1 )
>> -                    return p-1;
>> +                    return p;
>>                   if( p[2] == 0&&  p[3] == 1 )
>> -                    return p;
>> +                    return p+1;
>>               }
>>               if( p[3] == 0 ) {
>>                   if( p[2] == 0&&  p[4] == 1 )
>> -                    return p+1;
>> +                    return p+2;
>>                   if( p[4] == 0&&  p[5] == 1 )
>> -                    return p+2;
>> +                    return p+3;
>>               }
>>           }
>>       }
>
> the code as is in svn is wrong but your change is as well
> there can be 0001 and 001 startcodes, the return value has to point
> to the first byte of either

Is it wrong or does it work only with 0001 startcodes ?

-- 
Baptiste COUDURIER                              GnuPG Key Id: 0x5C1ABAAA
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