[FFmpeg-user] Unknown encoder 'libfaac'

Phil Rhodes phil_rhodes at rocketmail.com
Wed Jan 23 02:47:11 CET 2013

> I have downloaded the following FFMPEG version (built on Apr 16 2011 19:18:29 with gcc 4.5.2):
> http://ffmpeg.zeranoe.com/builds/win32/static/ffmpeg-git-1aeb88b-win32-static.7z
> I am currently trying to get the following command to work:
> C:\FFmpeg\bin\ffmpeg -i mp4_374.mp4 -r 20 -vcodec mpeg4 -b 150k -s qcif -aspect 16:9 -acodec libfaac -ab 48k -ar 22050 -ac 2 mp4_374_conv.3g2

I suspect you're likely to be told that your version of ffmpeg is too old to be supported, although it's my experience that AAC encoding is quite tricky to get working in any case. The name of the encoder (be it "libfaac" or "faac" or just "aac") seems to change very frequently and various distributed versions of ffmpeg either include or exclude it, or change what it's called. I believe there were at one time even different versions of the AAC encoder, at least some of which had performance issues.

Unfortunately as you've discovered merely downloading the required library and making it available is not enough to solve the problem (you'd have thought, but no). I believe (though don't quote me) that you would need to recompile the whole thing from source code which is an advanced topic and likely to be either beyond your ability, or at least not worthwhile on a windows PC where there are other, easier and possibly better ways of creating files with AAC audio, such as just doing it with a quicktime-compatible app.

Your best bet is either to do that, or try to find another version of ffmpeg that does include an AAC encoder. This may be difficult as it's often not possible to find out what a particular ffmpeg compilation does and does not include other than by trial and error.


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