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

[D Richard Felker III]

On Tue, Jun 01, 2004 at 03:30:56PM +0400, Vladimir Mosgalin wrote:
> On Tue, 1 Jun 2004, D Richard Felker III wrote:
> 
> DRFI>On Tue, Jun 01, 2004 at 06:38:32AM +0400, Vladimir Mosgalin wrote:
> DRFI>> DRFI>It's not suffering, but having a good monitor. On a good monitor, low
> DRFI>> DRFI>levels will be very close to one another. Otherwise dark areas will
> DRFI>> DRFI>have ugly banding from visible "steps" in the brightness level, and
> DRFI>> DRFI>everything just looks way too bright.
> DRFI>> 
> DRFI>> My monitor's brightness & gamma are calibrated to 2.5 gamma, and I see
> DRFI>> a lot of blocks and defects with vqscale=2 & original resolution
> DRFI>> (without scaling) on certain dvd rips. Of course, -vf pp removes them,
> DRFI>> but it removes details as well and blurs everything.  -vf noise=12uah
> DRFI>> improves picture, but not much.
> DRFI>
> DRFI>Turn gamma correction OFF!
> 
> *looks puzzled* Which gamma correction?
> 
> I mean that my monitor's brightness is tweaked to the right level, and

No, it's tweaked to the wrong level. That's the problem. Intensity in
movies is NOT linear; it's designed for the nonlinearity in CRTs. BTW
this is a GOOD thing, since you need more precision at lower
intensities or you'll see ugly bands/blocks.

> gamma is set to 1.01, 1.05 & 1.04 for rgb to get the correct 2.5 gamma.
> I use no gamma correction in mplayer, but I use -vf x11 to pick those
> values up.

I hope you don't normally use -vf x11, since it will tear!!

> OK, I'm gonna try xvid and tell if I see the same problems. Maybe really
> it's time to say goodbye to lavc. It may be good at middle & low
> bitrates, but when trying to encode dvds to get vhq rips, its behaviour
> isn't good.

This is nonsense. lavc gives much better psnr and much higher visual
quality (no artifacts whatsoever!) compared to xvid and divx, which
are about the same (after all they're from the same codebase).

> On the other hand, sometimes it everything goes well - when
> the picture is clean and simple. But on dvds with a lot of detais
> (which can be ripped, but the bitrate can get as high as was on original
> dvd - I only met that once, though) or on noisy or lq dvds, it doesn't
> preserve original quality. Quality drops a lot, at least with vqscale=2.
> To prevent questions: yes I use hqdn3d, but with lesser strength than
> default, and I don't use pp on dvds, it almost always only reduces
> quality. Blocking artifacts are very rare on dvds, mostly there are some
> other kinds of them...

I've seen bad blocking artifacts on DVDs, but noise is much more
common. The noise actually serves to mask out the blocking artifacts,
same as if you use -vf noise, but it wastes a LOT of space. Better to
denoise and add noise back during playback if you really insist. But
seriously... With a GOOD monitor, CORRECT brightness/gamma settings,
and proper encoding flags, you don't need anny noise/postproc. There
just aren't any artifacts.

Rich