[MPlayer-users] Re: lavc vs. xvid (and improving lavc quality)

[D Richard Felker III]

On Sun, May 30, 2004 at 11:54:24AM -0400, Jason Tackaberry wrote:
> On Sun, 2004-05-30 at 12:06 +0700, Evgueni V. Gavrilov wrote:
> > this comparison isn't correct because by default lavc doesn't create
> > B-frames, but xvid does.
> 
> It does?  I assumed it didn't because the man page says (under
> xvidencopts):
> 
>    max_bframes=<0-4>
>         maximum number of B frames to put between I/P frames (default=0)
> 
> I've definitely also noticed that xvid at quant=3 and lavc at quant=3
> yield very different bitrates.  I assumed that the numbers weren't
> really comparable between the two codecs, but it sounds like they're
> supposed to be.  Can B-frames really account for such a significant
> difference in bitrate?

Yes, because lavc by default uses double the quantizer for B frames. I
expect xvid does the same.

Rich