[Ffmpeg-devel] AAC bitrate

Dennis mediastream
Wed Feb 8 19:44:39 CET 2006

> used faac and faad as you can see, unfortunately, I can't produce AAC
> audio files (mp4 and 3gp) at ***8 kbit bitrate*** (which supposed to be the
> lowest setting for AAC- 1 channel/8000 Hz).
> The lowest ffmpeg was able to produce is 12.6 kbps AAC encoded file.
> ./ffmpeg -i 1.wav -acodec aac -ac 1 -ar 8000 -ab 8 -vol 150 test1.3gp
I just tried, and it seems to be producing audio at the correct bitrate.
Some time ago, I submitted a patch to set the cutoff frequency in faac.
The patch was committed in ffmpeg CVS on Tue Jan 10... Check if your
version of ffmpeg contains that change.

If it does and you are still not able to get the proper audio bitrate,
try to play with the cutoff frequency (-cutoff option of ffmpeg).

Anyway, are you sure that the bitrate of the audio produced by ffmpeg is
really 12.6kbps? (just checking... Be sure that you do not see a 4.6kbps
contained overhead ;-)

Copy this in your signature, if you think it is important:
                               N O    W A R ! ! !

Thanks Luca,

I've checked the header and it's at 8%, average bitrate is at 12.6, so it's
still far from 8kbps. Didi you use same command line to get 8kbps AAC?


More information about the ffmpeg-devel mailing list