Re: FFmpeg Xvid CBR or VBR with maxrate ? how ?

On Fri, 25 Mar 2005, Tom wrote:
> CBR means Contant Bit Rate so it may be possible to have the same 
> bitrate from the beginning to the end. But how ?! It's my question

You can't really encode CBR. Bitrate always depends on the input material, 
even if one has some methods to raise or lower the rate. You _can_ create 
CBR by padding up a VBR/ABR bitstream with garbage/null bytes to reach 
the bitrate you want to have. But there aren't many situtions where this 
is useful. 
 
> I'm trying since this week to make a mp4 video with ffmpeg and the xvid
> codec. It works well _BUT_ I'd like to limit the maximum bitrate because
> it's for streaming purpose. The bitrate must not exceed the allowed
> bandwidth (i.e: 80kb/s). So how to do CBR or VBR with a limited maximum
> bitrate ?

There is no "maximal" bitrate setting for XviD, because as CBR this isn't
a well defined term. What you should use is the VBV-settings which do  
what you really want: Setting a maximal number of bytes which have to be 
transfered within a certain time with a certain sized buffer. 

chl