[FFmpeg-user] 2 pass CBR or VBR not really fixing the bitrate?
ewilde at gntrains.com
Sun Jul 30 00:35:39 EEST 2017
At 10:51 PM 7/29/2017 +0200, Moritz Barsnick wrote:
>Have you tried using the identical video encoding settings for pass 1
>and pass 2? I seem to recall that that is important.
Interesting that you say that. I use "-an" for the first pass and then
"-codec:a libmp3lame -b:a 128k" for the second pass when doing two-pass
recording, and it works fine. My impression was that audio was
irrelevant for the first pass, since you were only building a set of
compression guide data for the video compressor to use in pass two.
> > Can anyone post an example of a case in which ffmpeg really gets CBR or
> say 110% VBR?
>I can't, but I can point out that ffmpeg mostly does ABR, not CBR.
The parameters above work for me. I tried VBR and could never get audio
that was synchronized properly with the video, using LAME. Since 128k,
CBR gives acceptable sound, to my ear, and good compression, I wasn't
about to lose sleep over it. There's too many other reasons why the
audio doesn't synchronize with the video. I didn't need a self-inflicted
The bitrate is pegged at 128 Kbps (according to MediaInfo) with this set
More information about the ffmpeg-user