[Ffmpeg-devel] Something wrong with rate control?

[Juan Jose Galvez]

Hi,

Ok, i've tried setting -maxrate, -minrate and -bufsize but it doesn't work. 
I get tons of rc buffer underflows and bitrate still isn't correct.

I have a snapshot from 2005-04-16 that works just by typing:
$ ./ffmpeg -i /c/samples/test.mov -vcodec mpeg4 -b 512 -acodec mp3 test.avi

I've also observed that this old snapshot encodes faster, don't know why. If 
I type the above line with the current CVS snapshot it generates a video 
with aprox. 3000kbps and encodes a lot slower. Another strange thing that 
happens is that the video generated with the current CVS snapshot doesn't 
play correctly in VLC (it decodes very slowly and VLC reports framerate is 
600) and this doesn't happen with the old snapshot. The same problems are 
happening with another snapshot I have from 2005-11-03.


Here is the command-line and output with the options you mentioned (in this 
case bitrate seems to stick at around 2200kbps):


$ ./ffmpeg -i /c/samples/test.mov -vcodec mpeg4 -b 512 -maxrate 512 -minrate 
0 -bufsize 50 -acodec mp3 test.avi
ffmpeg version CVS, build 3277056, Copyright (c) 2000-2004 Fabrice Bellard
  configuration:  --disable-debug --enable-mp3lame --enable-faac 
--enable-faad --enable-gpl --enable-a52 --enable-mingw32 --enable-pp 
--enable-memalign-hack --enable-x264
  built on Dec  1 2005 10:07:18, gcc: 3.4.2 (mingw-special)
Input #0, mov,mp4,m4a,3gp,3g2, from 'c:/samples/test.mov':
  Duration: 00:02:35.8, start: 0.000000, bitrate: 2925 kb/s
  Stream #0.0, 600.00 fps: Video: svq3, yuv420p, 640x268
  Stream #0.1: Audio: mp2, 44100 Hz, stereo
File 'test.avi' already exists. Overwrite ? [y/N] y
Output #0, avi, to 'test.avi':
  Stream #0.0, -1.#J fps: Video: mpeg4, yuv420p, 640x268, q=2-31, 512 kb/s
  Stream #0.1: Audio: mp3, 44100 Hz, stereo, 64 kb/s
Stream mapping:
  Stream #0.0 -> #0.0
  Stream #0.1 -> #0.1
[mpeg4 @ 00749638]rc buffer underflow
[mpeg4 @ 00749638]rc buffer underflowe=0.5 bitrate=1449.7kbits/s
[mpeg4 @ 00749638]rc buffer underflow
[mpeg4 @ 00749638]rc buffer underflow
[mpeg4 @ 00749638]rc buffer underflow
[mpeg4 @ 00749638]rc buffer underflow
[mpeg4 @ 00749638]rc buffer underflow
[mpeg4 @ 00749638]rc buffer underflow
[mpeg4 @ 00749638]rc buffer underflow
[mpeg4 @ 00749638]rc buffer underflow
[mpeg4 @ 00749638]rc buffer underflow
[mpeg4 @ 00749638]rc buffer underflow
[mpeg4 @ 00749638]rc buffer underflow
[mpeg4 @ 00749638]rc buffer underflow
[mpeg4 @ 00749638]rc buffer underflow
[mpeg4 @ 00749638]rc buffer underflow
[mpeg4 @ 00749638]rc buffer underflow
[mpeg4 @ 00749638]rc buffer underflow
[mpeg4 @ 00749638]rc buffer underflow
[mpeg4 @ 00749638]rc buffer underflow
[mpeg4 @ 00749638]rc buffer underflow
[mpeg4 @ 00749638]rc buffer underflow
[mpeg4 @ 00749638]rc buffer underflow
[mpeg4 @ 00749638]rc buffer underflow
[mpeg4 @ 00749638]rc buffer underflow
[mpeg4 @ 00749638]rc buffer underflow
[mpeg4 @ 00749638]rc buffer underflow
[mpeg4 @ 00749638]rc buffer underflow
[mpeg4 @ 00749638]rc buffer underflow
[mpeg4 @ 00749638]rc buffer underflow
[mpeg4 @ 00749638]rc buffer underflow
[mpeg4 @ 00749638]rc buffer underflow
[mpeg4 @ 00749638]rc buffer underflow
[mpeg4 @ 00749638]rc buffer underflow
[mpeg4 @ 00749638]rc buffer underflowe=0.8 bitrate=1715.2kbits/s

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