[FFmpeg-devel] H263 decoding crash

Pavel Pavlov pavel
Fri Jun 5 03:23:11 CEST 2009

Hello everybody,
I have some random crashes while decoding h263.

I use icl build of ffmpeg and can debug with visual studio. The problem
is that 
I only get crashes in release build, and only if I'm not attached with
the debugger.
I always get it in the same function after running a video call for a
Once I attach with the debugger after it crashed some of the variables
showing correctly, so I can't really see what's the problem.

For example, it crashes inside h263.c on line 4190

Here's the stack trace:

 	avcodec-52.dll!ff_h263_decode_mb(MpegEncContext * s=0x01068c10,
short [64]* block=0x06ce48c0)  Line 4190 + 0x11 bytes	C
 	avcodec-52.dll!decode_slice(MpegEncContext * s=0x00000000)  Line
221 + 0x7 bytes	C
 	avcodec-52.dll!ff_h263_decode_frame(AVCodecContext *
avctx=0x01068280, void * data=0x01068620, int * data_size=0x015af8d8,
AVPacket * avpkt=0x015af830)  Line 653	C
 	avcodec-52.dll!avcodec_decode_video(AVCodecContext *
avctx=0x00000000, AVFrame * picture=0x015af8f8, int *
got_picture_ptr=0x015afcc4, const unsigned char * buf=0x005ac98a, int
buf_size=17203840)  Line 563 + 0x6c bytes	C
>	EC-09.exe!H263DecoderStruct::Transform(void * pData=0x07aa5954,
int nSize=1706, SAL::MediaSample & Sample={...},
SAL::SmartPointer<SAL::MediaHandler> p={...})  Line 459 + 0x20 bytes

stack trace doesn't make much sence, as my code calls
avcodec_decode_video(0x01068620, 0x01068620, &nResult, 0x07aa5954,
but on the next line it shows AVCodecContext * avctx=0x00000000

Just before ff_h263_decode_mb is called, in file h263dec.c:221 inside
function decode_slice
there is a commented out printf:
//            s->mb_skipped = 0;
//printf("%d %d %06X\n", ret, get_bits_count(&s->gb), show_bits(&s->gb,
Was someone getting some sort of problems and that's why there is this
printf to trace?

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