[FFmpeg-devel] [PATCH] correct MPEG video parser not to return incomplete frames

[Baptiste Coudurier]

On 08/02/2009 07:53 AM, Michael Niedermayer wrote:
> On Sun, Aug 02, 2009 at 03:58:59PM +0200, Ivan Schreter wrote:
> [...]
>> @@ -146,7 +153,12 @@
>>       /* we have a full frame : we just parse the first few MPEG headers
>>          to have the full timing information. The time take by this
>>          function should be negligible for uncorrupted streams */
>> -    mpegvideo_extract_headers(s, avctx, buf, buf_size);
>> +    if (mpegvideo_extract_headers(s, avctx, buf, buf_size)<  0) {
>> +        /* garbled frame, ignore (possibly first read after seek) */
>> +        *poutbuf = NULL;
>> +        *poutbuf_size = 0;
>> +        return next;
>> +    }
>>   #if 0
>>       printf("pict_type=%d frame_rate=%0.3f repeat_pict=%d\n",
>>              s->pict_type, (double)avctx->time_base.den / avctx->time_base.num, s->repeat_pict);
>
> as already said elsewhere, its not the job of parsers to discard data
> it would break decoders that are capable to decode damaged frames, like
> our decoder.

Well there is another problem, the partial frame it will be kept during 
stream copy, I don't think anybody will want that when extracting mpeg-2 
from TS or PS.

IMHO if picture start code is missing, if pict_type is 0 after 
extract_headers, you can reasonably discard the data.

[...]

-- 
Baptiste COUDURIER                              GnuPG Key Id: 0x5C1ABAAA
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