[MPlayer-dev-eng] Removal of backing store

[Vladimir Mosgalin]

Hi Stephane Marchesin!

 On 2008.08.23 at 02:43:49 +0200, Stephane Marchesin wrote next:

> > And what exactly does composite has to do with backing store?
> 
> The link is that when you use an EXA driver, windows with a backing
> store flag are redirected. From then you can't use the hw overlay.

Then it's bug in nouveau driver. I don't observe anything like that on
intel. Can't check ati driver for R3xx/R4xx with EXA, though.

> Hmm, compiz doesn't use backing store, it's mplayer that enables it.
> And yes, the flag still exists for backwards compatibility.

Well.. isnt' mplayer merely setting a hint, that it could use backing
store? And it's up to X server whether to actually utilize one.

What I mean, is that X should just ignore that hint with compiz, there's
no need in it.

> Sure, and it made no difference. So again, what good does it do ?

You missed my point. I agree that if it improves things a lot in one
configuration and doesn't hurt in others, it should be removed. But can
you honestly say that all your patch does is performance improvement for
your case? The improvement is pretty big, so how can you be sure that it
produces no slowdowns and no ill-effects on all other supported
configurations?

> > Intel provides two xv adaptors, one for hardware overlay and one for
> > textured video. Not sure about fallback, probably there isn't (when you
> > specify adaptor directly).
> 
> Intel has the textured adapter as default, and overlay as 2nd. So you
> will use the textured adapter usually. This means you don't encounter

Sure, I know that. And I use overlay - it gives slightly better
performance without compiz, and MUCH better performance with it.

> the issue by default. But it you do the following :
> - mplayer -vo xv:port=[the overlay port]
> - make the mplayer window transparent or whatever under a composited
> desktop (using xcompmgr + transset for example).
> you will get a blue window. This could be fixed if intel added an
> automatic fallback (except it would fallback all the time because of
> backing store, like nouveau).

Yes, obviously. It does exactly like it should. If I force overlay
instead of default textured video xv port, it gives funny effects in
compiz - effects operate on blue window, not on video. Not that it
matters much, since when you don't make window transparent or move it or
switch tasks you can watch video without any problems. And the only
alternative, textured video, becomes really slow when effects are used
(i945 + 800 mhz cpu + single-channel ram isn't exactly a fastest combo).

But I don't care about effects for video window, I care about fast video
output. And isn't that exactly the thing you are trying to achieve? So
the question is, why are there no problems with intel driver without
your patch (I don't have build env on my notebook, so I can't check
patched version right away, sorry)? intel can manage both textured video
and overlay usage in EXA mode perfectly with and without compiz, so why
does nouveau needs your hack? It really sounds like a bug in nouveau.

> > IOW, are you sure your fix applies to anything but older nvidia cards?
> >
> 
> I think for now it applies to nouveau only. Once this is fixed, other
> drivers can enable their hw overlay in a composited situation too, and
> everyone wins.

intel already does that, so why nouveau can't?

And actually I meant a different thing. Newer radeon cards don't support
hw overlay, but doesn't the same applies to newest intel and nvidia
cards too? For example, intel driver doesn't provide overlay xv port for
X3500 & X4500 (maybe for X3000 too).

-- 

Vladimir