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When I use ffmpeg to convert an audiofile with the option

-acodec libfaac -ab 192k 

and use

ffmpeg -i 

on that file afterwards to get the audio file information, it tells me

bitrate: 152 kb/s

Why ist this? Do I miss something here? If I want to convert a file with a bitrate of 192kb it should give me 192 kbit after the conversion, shouldn't it?

Or: How do I get the 192 kbit rate then?

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I tried this with on my PC and got similar results. Here's my source file: teeks99.com/examples/audio_check.flac And my result file: teeks99.com/examples/audio_check_out.flac I've got a relatively recent version of ffmpeg (SVN-r26068, built with --enable-libfaac), but a somewhat older version of libfaac0 (1.26-0.1ubuntu2 maverick default). –  teeks99 Jan 13 '11 at 19:26
    
Noone? So this seems to be a bug. Where do I have to report this as bug? (I couldn't find a bugtracker for ffmpeg aac support ...) –  piedro Jan 23 '11 at 9:11
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1 Answer

up vote 1 down vote accepted

I can't provide any further explanation, but several places (e.g. [1]) mention:

Note that the maximum average bit-rate (what -ab specifies in the context of libfaac) is 152 kbit/s. Setting this higher will be ignored and 152 kbit/s will be used.

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THx for your hint, I wonder how the quality is compared to which mp3 compression. With itunes we always used 192 aac compression. seems a bit low to have 152k only ... but thanks for your answer! –  piedro Aug 19 '11 at 13:33
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