[MPlayer-dev-eng] Removal of backing store

[Stephane Marchesin]

On Fri, Aug 22, 2008 at 9:02 AM, Reimar Doeffinger
<Reimar.Doeffinger at stud.uni-karlsruhe.de> wrote:
> On Fri, Aug 22, 2008 at 02:01:20AM +0200, Stephane Marchesin wrote:
>> - most importantly, backing store prevents from using a real hardware
>> overlay (as opposed to blitter/texture adapters) because this forces
>> window redirection. You then have to fallback to using the blitter
>> port, which is a lot slower than a native hardware overlay.
>> Also FWIW, neither vlc nor xine (with its xine-ui frontend) enable
>> backing store, as seen in the following files/places:
>> http://git.videolan.org/?p=vlc.git;a=blob;f=modules/gui/skins2/x11/x11_window.cpp;h=03ec09fe978a3e048ff1e32f52be9b9ce9cd738a;hb=HEAD
>> http://xine.cvs.sourceforge.net/xine/xine-ui/src/xitk/videowin.c?revision=1.237&view=markup
>> (look for XCreateWindow calls in both)
>
> There must be some things missing in your description, first I _know_ MPlayer
> never ended up using the blitter for me, which is obvious due to
> 1) vsync working (at least when manually choosing a non-overlay port vsync is not supported)
> 2) performance being better much better than with any other method
>

But was that with an EXA-enabled driver ? In which case it's
impossible to use the hw overlay (enabling it would be a bug in the
driver, since the window is redirected the driver can't use the
overlay because effects like transparancy could be applied).

> Actually, your last numbers with the binary nvidia drivers seem
> This was tested with a NVidia TNT2. And the situation when using the
> xvidix drivers is basically the same for what I can tell.
> I am not generally opposed to it, but so far my summary of the situation would be
> "nouveau drivers behave stupidly when backing store is enabled, so disable
> it in MPlayer so nouveau does not need to be fixed".

I _write_ the nouveau driver. If there was a way to fix it in there,
believe me I would have done it. But it's an issue with mplayer, so I
brought it here.

> I guess your opinion is that nouveau is behaving as it should, but without
> arguments it is a weak position to change code that has worked well for many
> years and nobody might truly no what kind of effects changing it might really
> have (e.g. does disabling backing store not mean that MPlayer will have to redraw
> the window each time it is moved instead of possibly using 2D acceleration
> during the moving? If so, this might cause flickering).
>

Backing store doesn't affect Xv windows.

Really, I don't understand why you refuse to change that flag. It buys
you nothing, and makes some driver/hw combinations slower. So what's
the point ?

Stephane