[MPlayer-dev-eng] [RFC] change lacv's MPEG-4 encoding options defaults

[Guillaume POIRIER]

Hi,

On 12/29/05, Ivan Kalvachev <ikalvachev at gmail.com> wrote:
> 2005/12/28, Guillaume Poirier <docmaintainerwannabe at laposte.net>:
> > Hi there,
> > Wouldn't it be nice if lavc's default's were the best speed/quality
> > tradeoff?
> >
> > Currently, lavc's defaults are pretty much "blazing speed at all costs",
> > which I don't think is a good idea since it doesn't help promoting lavc
> > as a high quality codec, but just "good very fast codec".
> >
> > I'd like lavc to default to vcodec=mpeg4:mbd=2:trell:v4mv:turbo
> >
> > In my experience
> > (http://tuxrip.free.fr//MPlayer-DOCS-HTML/en/menc-feat-enc-libavcodec.html#menc-feat-mpeg4-lavc-example-settings),
> > it was only 0.74dB below optimal quality while being several times
> > faster than optimal quality.
> >
> > I'd like to consider adding vmax_b_frames=1, vb_strategy=2 and dia=-1,
> > but I have not made any recent speed/quality tests recently.
> >
> > Maybe with latest Michael's commits, further tests should be done to
> > find the new best speed/quality tradeoff, but until then, what do you
> > guys think?
>
> I must say that i am also against this change.
>
> 1. 'turbo' overrides 'mbd' and set it to 0. It also disables v4mv,
> qpel, trellis,cbp,mv0,qprd and makes search diamand really small. In
> short the given line have only benefith because 'turbo' sets mb_cmp=2
> (hadamand).

Turbo only removes options in the first pass. I doesn't do anything at
all in pass 2 or 3.

Actually, I don't care too much if turbo is not on by default.


> I think mbd=2 is not good default because (AFAIK) it is supposed to
> work for bitrate only.

Never hear of such thing. vhq == mbd=1, and it works fine in any mode
(bitrate or constant quant).


> 2. ATM there aren't no-options. It meas that for every enabled option
> there must have no-option that disables it.

This can be added easily, can't it? I've done it for XviD, Loren has
done it for x264, so it can (and probably should) be done for lavc.


> There is thread that tries
> to use ffmpeg options directly in mencoder, that I consider good idea,
> but it will make even harder to implement the no-options.

I don't under sand what you mean here.


> It would be much better to have presets.

Looks like this will have to be the way to go. That's fine with me.

Guillaume
--
Life is pleasant. Death is peaceful. It's the transition that's troublesome.
    Isaac Asimov (1920 - 1992)

MPlayer's doc is offline. Find some fresh one here:
http://tuxrip.free.fr//MPlayer-DOCS-HTML/en/
http://tuxrip.free.fr//MPlayer-DOCS-HTML/fr/