[libav-tools] AAC encoded files show "0 kbps" average bitrate.

Oliver Hookins oliver at soundcloud.com
Tue Oct 2 14:35:24 CEST 2012


I've been doing some testing of AAC encoded audio files with both
avconv and the Nero AAC encoder tool and have been having some trouble
playing them back. I'm not sure if this is a red-herring or not but
all of the files generated by avconv report the average bitrate of the
files as zero, despite showing a non-zero average during encoding

I also tried a few of the different AAC codecs avconv supports
(libfaac, libvo_aacenc, libfdk_aac) just to confirm there was nothing
funky going on there:

# mp4info 1mT1O677gwdP-libfaac.mp4
mp4info version trunk-r479
Track	Type	Info
1	audio	MPEG-4 AAC LC, 108.321 secs, 0 kbps, 44100 Hz
 Encoded with: Lavf53.21.0

Compare this with the Nero encoded file:

# mp4info 1mT1O677gwdP-nero.mp4
mp4info version 2.0.0
Track	Type	Info
1	audio	MPEG-4 AAC LC, 108.344 secs, 96 kbps, 44100 Hz
 Encoded with: Nero AAC codec /

I verified this in the headers with mp4file --dump and a hex editor.
There have been a few threads about this topic in the past and
apparently there was a commit last year [1] that fixed it. Given this,
I'm not sure why it is still happening (unless a regression has
occurred). Any thoughts?

Best Regards,

[1] http://git.videolan.org/?p=ffmpeg.git;a=commit;h=0ba8485666f532f2dbab716f74e1be1189102c89

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