[MPlayer-users] Re: divx 6

Matthias Wieser mwieser at gmx.de
Thu Apr 27 03:24:04 CEST 2006


Corey Hickey wrote:
> Matthias Wieser wrote:
> > Am Donnerstag, 20. April 2006 21:00 schrieb Corey Hickey:
> >> Szabolcs Nagy wrote:
> >>> hello
> >>>
> >>> is there any way to use the linux divx 6 binary codec with mencoder ?
> >>> http://labs.divx.com/DivXLinuxCodec
> >>
> >> No, though if someone were to add support it would be useful for
> >> testing and comparison.
> >>
> >> In any case, you'll probably get better performance and/or quality by
> >> using XviD or libavcodec MPEG-4, both of which are well-supported in
> >> mencoder.
> >
> > Xvid and DivX 6.1 seem to be much faster at better quality than
> > libavcodec. http://www.doom9.org/index.html?/codecs-main-105-1.htm
>
> That depends, and a few things have changed since the Doom9 comparison.
>
> 1. Lavc has slightly better overall encoding than it used to.

Same is true for Xvid.

> 2. XviD used to avoid B-frames where they would be detrimental much
> better than lavc. With vb_strategy=2, lavc does just as well, though
> much more slowly.

"exactly as well" or "it tries to do as well"? Additionally last time I have 
tested vb_strategy=2 it has been buggy.

> 3. Lavc places I-frames slightly better than before, with sc_factor=6.

Another option which has to be adjusted manually. Xvid just works.


> 4. XviD's ratecontrol adapts to motion much better.

Very true.

> Now, lavc can use XviD ratecontrol internally. Alternatively, a more
> XviD-like ratecontrol equation for lavc is vrc_eq=(tex+10^8*mcVar)^0.6

Then why not just use Xvid?


> At this point, taking the above considerations into account, lavc will
> produce video that is nearly indistinguishable from that encoded by XviD
> (and certainly looks just as good), but at a much slower speed.

That's why I have written "Xvid and DivX 6.1 seem to be much faster at 
better quality than libavcodec".


> ...there's a bit more, though: I haven't mentioned qns. qns=2 makes
> sharp high-contrast edges in encoded material look much better, but
> slows down the encoding process dramatically.

Much better? The doom9 comparison showed that lavc had problems with fine 
details. But high-contrast edges were no problem for any of the codecs.


> So, here's my current summary view on all this:
>
> - by default, lavc encodes much faster but looks somewhat worse than XviD

"much faster"? The default options of lavc are extremly low quality. Making 
xvid as low quality makes it even faster, so I don't know which one is 
faster in the end. Adjusting lavc and xvid to produce comparable medium 
quality shows that xvid is faster (my own benchmarks) than lavc. With high 
quality options (doom9) xvid and divx are faster, too.

> - if you enable most high-quality options, lavc can look as good as
> XviD but encodes much more slowly

Probably right. But do you have any proove for "as good"?
Does lavc support gmc? Does it support (a usability feature) like cartoon 
mode?

> - if you enable qns as well, lavc can look better than XviD but encodes
> even more slowly

The doom9 contest did not use Xvid's highest quality options.


Regards,
  Matthias




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