[FFmpeg-user] 2 pass CBR or VBR not really fixing the bitrate?

Manuel Tiglio tiglio at icloud.com
Mon Jul 31 04:52:08 EEST 2017

Hi there, 

I apologize for my delay in replying, I found that the mailing list messages were being sent to my junk folder :-(

> On Jul 29, 2017, at 1:51 PM, Moritz Barsnick <barsnick at gmx.net> wrote:
> On Sat, Jul 29, 2017 at 13:16:07 -0700, Manuel Tiglio wrote:
>> ffmpeg -I <input> -c:v libx264 -pass 1 -f mp4 /dev/null
>> ffmpeg -I <input> -c:v libx264 -b:v avg -maxrate max -minrate min -bufsize buf -pass 2 <output> 
> Have you tried using the identical video encoding settings for pass 1
> and pass 2? I seem to recall that that is important.

Yes, I have tried. All kind of combinations. Interestingly enough, different options do make a difference, in the sense that the results are slightly different,  but still no luck in trying to control the bitrate. 

>> 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.

Thanks for sharing! But apparently I cannot even do 110% VBR, it seems to somewhat control the bitrate fluctuations but far from what it should do. I would imagine that people have already gone through this, so I am kind of puzzled. 

Thanks again so much. 


> Moritz
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