[FFmpeg-devel] [PATCH] Fix interlaced MPEG2 decoder crash (issue2367)

[Anatoly Nenashev]

On 23.12.2010 18:33, Michael Niedermayer wrote:
> On Thu, Dec 23, 2010 at 11:19:55AM +0300, Anatoly Nenashev wrote:
>    
>> On 23.12.2010 03:36, Michael Niedermayer wrote:
>>      
>>> On Thu, Dec 23, 2010 at 02:16:21AM +0300, Anatoly Nenashev wrote:
>>>
>>>        
>>>> Hi!
>>>> Full problem description available on https://roundup.ffmpeg.org/issue2367.
>>>> After some research I've found that sample file(exploit.bin) conflicts
>>>> with specification in the following lines:
>>>>
>>>>          
>>> is anything capable of playing this file?
>>>
>>> or is it a damaged file?
>>>
>>> how has this file been created exactly?
>>>
>>>
>>>        
>> Sample file is truncated version of the original file which has been
>> grabbed from Optelecom Siqura C-60.
>> I've left only two first pictures to minimize the problem. Original
>> sample uploaded to
>> ftp://upload.ffmpeg.org/MPlayer/incoming/interlaced_mpeg2/interlaced_mpeg2.bin
>> It can be successfully decoded by libmpeg2 tools. By the way, libmpeg2
>> reports errors for exploit.bin and returns no frame but don't crash.
>>      
> This does not awnser my question.
> Is this file valid or is it damaged?
> Or worded differently, is there a matching player from the manufactor whos
> hardware generated this file which is then capable of displaying something
> for this frame?
>
> If something can play this file then the patch is 100% wrong
> if nothing can play this file then the patch is still wrong because you drop
> the previous I field that has been decoded correctly.
>    

Manufactor gives access to video source through the Web Browser. This 
file has been grabbed from the stream in local network. I don't think it 
is damaged but it looks like it doesn't contain some data from the start 
of connection. Close look into the stream shows that sometimes there is 
double I-frames available (for both fields). May be this is the place 
where decoder must start to work. I've made truncated original stream 
that starts from double I-frames and FFmpeg works fine on it.