[MPlayer-users] Re: mencoder lavcopts for decreasing filesize

[Matthias Wieser]

Hi,

Am Samstag, 11. Februar 2006 22:08 schrieb Ellis Whitehead:
> Quick summary:
> If you take a simple lavcopts of:
>  vcodec=mpeg4:vbitrate=1500:keyint=125:vqmax=5:vhq
> and add:
> 
> mbd=1:vmax_b_frames=2:vi_qfactor=-0.8:preme=0:vqsquish=0:vrc_strategy=0
> then you'll get about a 5% filesize reduction.  Add "-vf hqdn3d" to the
> mencoder command line and you'll get another 5% (approximately, of
> course, depending on video source).

That's bad because you should not get any filesize reduction. Why? Because 
of "vbitrate=1500". If you see a filesize reduction it is because of 
Mencoder's filesize tolerance (1MByte) or "vqmax=5" or a bug.


> 1. mencoder lavcopts for decreasing filesize

How to do it properly:
  Create videos with equal PSNR values but different lavc options.
  Finding the bitrate which results in a particular PSNR is an iterative
    process.
  Calculate bitrate reduction.

If you want to take video filters or things like that into account
you have to consider that the PSNR values printed by mencoder are 
meaningless. In this case use Mplayer/main/TOOLS/psnr-video.sh

Regards,
  Matthias