[MPlayer-dev-eng] Removal of backing store

[Vladimir Mosgalin]

Hi Stephane Marchesin!

 On 2008.08.24 at 18:50:45 +0200, Stephane Marchesin wrote next:

> Because if the window is made transparent for example, you can't use a
> real hw overlay. And the driver has no way to know which is the
> current situation, since this is the compositing manager's business.

You are talking about old cards, right (since newer ones don't have hw
overlay)? And most likely they're used in older systems. I doubt that
you'll be happy when your video playback suddenly slows down a lot when
you start moving window over desktop or setting its transparency. And if
it doesn't matter for you, just use textured video in any case..

Honestly, I'd prefer system which doesn't magically switch video
rendering backends behind my back, but always provides adequate level of
performance.

> Read what I said, the hw overlay's not default, so you get slow speed
> for everyone as default. People who want to use the hw overlay anyway
> will get blue screens in some situations.

I understand your logic, but IMHO it's too far from real life. The
speed penalty for using textured video in non-composed environment
should be pretty small. And if it isn't, it means that you have really
old card or you're playing high res video, in which case textured video
in composed environment is absolutely no-go - it'll be slow as hell.

In my case, even 640x272x25 video (window output, no scaling) becomes
unwatchable with textured video when compiz is running. If some effects
are over it, it's almost slideshow. However I can play 720p video (with
-vf-clr option and 95% cpu load) on the same system through hw overlay,
with or without compiz and through textured video when compiz isn't
running.

> So you say people should be able to understand what happens with
> window redirections and Xv ? Considering you don't seem to understand
> it fully, do you expect others to ?

No, but they'll ask on forums or something. After all, the target
auditory isn't that big (people with older cards using compiz).

Also this is pretty minor issue comparing to what happens to other
opengl applications under compiz, I must say.. (we're all eagerly
waiting for DRI2).

> Yes, and we can have a "best effort" choice, one with an adapter that
> automatically switches from hw overlay to blitter when the window is
> being redirected. This means, inside a compositing manager, that you
> get :
> - when the window is opaque and untransformed (that's called
> "unredirection"), the hw overlay
> - otherwise, the blitter/textured adapter
> This is an optimal situation, I don't understand why you criticize it
> ? Please enlighten me.

(read before)

Anyway this is getting quite OT. My original point was that hw overlay
vs. textured video and direct output vs. redirected shouldn't have
anything to do with backing store, and behavior of intel drivers proves
it, as I see it.

What I prefer and what do you prefer are different things, if you like
that "best effort" choice that you describe then it's fine (though I
certainly hope it can be turned off, because I think it's useless). But
if something like backing store can hurt it, it's driver bug. This fact
doesn't have anything to do with our preference ;)

> >> models don't), r100->r300 (that is up to X800) and i810 -> i915 (there
> >
> > Well my 945 certainly has it..
> >
> i945 the same as i915 for most stuff (i945 is a marketting name). The
> next "improvement" step is i965. Please read up on intel hw before
> nitpicking on small stuff, you're just sidetracking the real issue.

Oops sorry, forgot to add smiley to that remark ;)

Btw even if you say it's the same, I find them quite different - some
effects in compiz are really slow on 915, and some complex ones aren't
available - but they work on 945 and pretty fast, too. I'm pretty sure
about that because I use 915 system with compiz every day.

-- 

Vladimir