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

[Matthias Wieser]

Am Samstag, 29. Mai 2004 20:49 schrieb Jason Tackaberry:

> My biggest beef with lavc is the blockiness in muddy areas and areas of
> solid colors.  This is an oft observed phenomenon with lavc.  Consider,
> for example, a grey wall in the background that is slightly out of
> focus.  Even at vqscale=2, the blockiness is noticeable and annoying.
> At that quality/bitrate, where areas of high detail are preserved
> excellently, a background of "dancing blocks" is terribly jarring.

The libavcodec developers assume that the requirement to use 
postprocessing filters is known. Without postprocessing the quality of 
libavcodec is quite bad. With default postprocessing filters of Mplayer 
(pp=de) the luminance will be changed, but you won't see those "dancing 
blocks".

> After reading an article on doom9 that stacked up a number of codecs, I
> decided to compile xvid into mplayer and give that a try.  I was
> immediately able to see a difference: xvid's artifacting is much more
> pleasant to my eye.

The xvid people know that it's not psnr what matters but where you spend 
your bits. Bits spent for the sky or things like that don't improve psnr 
much but improve visual quality. At least if you don't know if the person 
watching the movie is going to use postprocessing filters.


> Unfortunately, xvid is also nearly an order of magnitude slower than
> lavc.

Which version of xvid? 1.0?

> I picked xvid 5 out of 5 times, although 2 of the clips were close
> calls.

Nearly every comparison attests that. But don't mention it on MPlayer ML, 
because they will say that the comparison has been done wrong.

> I suppose at such high bitrates, PSNR is always going to be
> good enough, and so becomes irrelevant.

At least there are better tests for visual quality but I only know 
expensive commercial tools.


> I used these options for lavc:
>    -lavcopts
> vcodec=mpeg4:vqscale=1.8:v4mv:mbd=2:trell:mv0:autoaspect:psnr and for

Have you tried qpel?

Matthias