[FFmpeg-devel] [PATCH] Fix decoding crash on some trashed interlaced MPEG2 streams. This fixes issue 2367.

[Anatoly Nenashev]

On 18.02.2011 18:38, M?ns Rullg?rd wrote:
> Anatoly Nenashev<anatoly.nenashev at ovsoft.ru>  writes:
>
>    
>> On 18.02.2011 15:26, M?ns Rullg?rd wrote:
>>      
>>> What is the actual problem you are trying to detect?  Missing reference
>>> picture?
>>>
>>>
>>>        
>> The problem is available when second field of first decoded interlaced
>> picture has P-type. In this case inter prediction can be done from the
>> first field of current picture (works fine) or from the second field
>> of previous  picture (crashes decoder). Sample exploit attached to
>> issue 2367. This sample was specially prepared to show the problem.
>>      
> Couldn't that be checked per frame instead of per MB?  Sure, doing it
> per MB might allow decoding some blocks, but is that really worth it?
>
>    
I don't know how to  made this check per frame because there may be some 
macroblocks predicted from the first field of current picture and the 
other predicted from the second field of previous picture. I can't find 
this information without decoding each macroblock.