[MPlayer-cvslog] CVS: main/libmpcodecs ve_lavc.c,1.111,1.112

[Guillaume Poirier]

Hi,

On Wed, 2 Mar 2005 15:08:45 -0500, D Richard Felker III
<dalias at aerifal.cx> wrote:
> On Wed, Mar 02, 2005 at 08:28:45PM +0100, Guillaume Poirier CVS wrote:
> > CVS change done by Guillaume Poirier CVS
> >
> > Update of /cvsroot/mplayer/main/libmpcodecs
> > In directory mail:/var2/tmp/cvs-serv21224/libmpcodecs
> >
> > Modified Files:
> >       ve_lavc.c
> > Log Message:
> > 35% faster turbo mode with 0.01dB drop. Based Loren Merritt's suggestions.
> > Next step would be to make turbo mode accept a "quality" argument to control the
> > speed vs quality tradeoff.
> 
> If you're experimenting with this, could you see what happens if you
> encode pass1 by scaling way down (e.g. 1/2 width and height) with
> vf_scale, and then encode pass2 at full size? i.e. does the psnr
> significantly drop? It might be necessary to do some renormalization
> of the data in the log file for such a hack to work, but I suspect if
> done correctly it might, and of course it would make another 50%
> speedup or something...

That's a nice idea that you've got here... Well, I'd say that my
understanding of MPlayer's code makes me wonder how it might be
possible to scale down the video with parameters given in ve_lavc, but
I have to admit the idea is appealing...

As far as the renormalization is concerned, I guess a constant-quant
(like vqscale=2) encode for the first pass could do the trick,
couldn't it?
Well, reading x264's section of the manpages, it kind of states that
should a first pass be done with constant quants, it's better if the
constant quant used is close to average quants in the resulting video,
so I don't know what I should do...

Anyway, thanks Rich for the idea!

Regards,
Guillaume