[Ffmpeg-devel] ffmpeg hanging when transcoding mpeg4

[Aaron Williams]

Michael Niedermayer wrote:
> Hi
>
> On Sat, Oct 21, 2006 at 02:32:11AM -0700, Aaron Williams wrote:
>   
>> I am trying to transcode a video for a friend into MPEG2 for use with a
>> hardware MPEG decoder and am running into problems with FFMPEG stopping
>> at the same place in the video and consuming all of the CPU.  I seem to
>> be unable to do any source level debugging with gdb (even when compiled
>> with -O2 and -g) so I cannot find the source of the hang.  It always
>> occurs at about time 236.2 in the file.
>>     
>
> you do use ffmpeg_g for debugging right?
> and maybe try valgrind
>   
I do not see ffmpeg_g.  Do I need to do something special in configure
to build that?  Also, valgrind is reporting problems, but again there
appears to be no debugging information.

I do see the following though:
==20851== Conditional jump or move depends on uninitialised value(s)
==20851==    at 0x4DEE61F: ff_mpeg4_decode_mb (in
/usr/local/lib/libavcodec.so.51.20.0)
==20851==    by 0x4DFFB83: (within /usr/local/lib/libavcodec.so.51.20.0)
==20851==    by 0x4E00F40: ff_h263_decode_frame (in
/usr/local/lib/libavcodec.so.51.20.0)
==20851==    by 0x4CCF222: avcodec_decode_video (in
/usr/local/lib/libavcodec.so.51.20.0)
==20851==    by 0x40A5D3: (within /usr/local/bin/ffmpeg)
==20851==    by 0x40C2C4: main (in /usr/local/bin/ffmpeg)


I can get the file to transcode if I scale it to certain resolutions. 
The source is MPEG4 at 720x380, encoded with an aspect ratio of 16:9. 
If I scale it to 720x480 it hangs.  If I scale it to 720x352 and add 64
pixels of padding above and below it works.  It seems to be a bug
somewhere in the scaling code.  If I convert to h264 instead of mpeg2
then it seems to go through OK.

I think the original video was improperly scaled for a 16:9 aspect ratio
as well.

I am trying to cut the size of the source file as well so I can post a
link to a smaller file, but this is failing as well:

/usr/local/bin/ffmpeg -i DCF-Brick-DivX-high.avi -vcodec copy -acodec
copy -y -ss 220 -t 30 DCF-Brick3-hang.avi
FFmpeg version SVN-r6280, Copyright (c) 2000-2006 Fabrice Bellard, et al.
  configuration:  --enable-libogg --enable-vorbis --enable-faad
--enable-faac --enable-xvid --enable-x264 --enable-a52 --enable-dts
--enable-shared --enable-dc1394 --enable-gpl --enable-mp3lame
  libavutil version: 49.0.1
  libavcodec version: 51.20.0
  libavformat version: 50.6.0
  built on Oct 21 2006 02:51:51, gcc: 4.1.0 (SUSE Linux)

Seems that stream 0 comes from film source: 29.98 (65534/2186) -> 29.97
(2997/100)
Input #0, avi, from 'DCF-Brick-DivX-high.avi':
  Duration: 00:07:09.6, start: 0.000000, bitrate: 865 kb/s
  Stream #0.0: Video: mpeg4, yuv420p, 720x380, 29.97 fps(r)
  Stream #0.1: Audio: mp3, 48000 Hz, stereo, 128 kb/s
Output #0, avi, to 'DCF-Brick3-hang.avi':
  Stream #0.0: Video: mpeg4, yuv420p, 720x380, q=2-31, 29.98 fps(c)
  Stream #0.1: Audio: mp3, 48000 Hz, stereo, 128 kb/s
Stream mapping:
  Stream #0.0 -> #0.0
  Stream #0.1 -> #0.1
Press [q] to stop encoding
error, non monotone timestamps 9170 >= 9170
error, non monotone timestamps 9173 >= 9173
...
frame=  900 q=0.0 Lsize=    3589kB time=250.0 bitrate= 117.6kbits/s
video:3039kB audio:476kB global headers:0kB muxing overhead 2.103378%

-Aaron