[FFmpeg-user] 5.1 sound aac

Adam Kłobukowski adamklobukowski at gmail.com
Mon Nov 21 18:51:35 CET 2011


I'm reencoding 5.1 sound from ac3 to aac. I have it scripted to reencode 
a lot of different videos.

I use ffprobe to get source bitrate, and use it for output bitrate.

So, with source audio bitrete reported as 384k I reencode it like this:

ffmpeg -threads 4 -i video.mkv -vcodec copy -acodec aac -ab 384k -strict 
experimental -f mp4 video.mp4

But, it is wrong. I'n fact, with 5.1 sound bitrate is divided per 
subchannel, so effective bitrate is much lower (and it can be heard).

There are 2 possibilities:
1. ffprobe reports wrong bitrate
2. ffmpeg uses wrong bitrate
3. I'm wrong and do not understand what it all means.

Which one is true?


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