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I want to encode an audio file to AAC, using libfdk_aac, and I'm wondering about the quality parameters. I want to use variable bitrate encoding, not constant bitrate.

It seems I can specify the quality either with the -vbr N parameter (with N=1..5) like this:

ffmpeg -i input.flac -acodec libfdk_aac -vbr 4 output.m4a

Or using the -q:a N parameter (here N=0..9) like this:

ffmpeg -i input.flac -acodec libfdk_aac -q:a 7 output.m4a

How are these two related, is there a substantial difference? Do specific -q:a values correspond to certain -vbr values, or is it a different encoding approach altogether?

RocketNuts
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1 Answers1

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My bad, after some experimenting I found out that the -q:a parameter does not apply to the libfdk_aac encoder, only to ffmpeg's native AAC encoder (which is inferior).

Hence always use -vbr with libfdk_aac. Leaving this here for reference in case anyone else may ever be wondering about this.

RocketNuts
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