Re: iBook and playing DVDs
On Mon, 2002-05-13 at 22:04, Rogério Brito wrote:
> On May 12 2002, Michel Dänzer wrote:
> > On Sun, 2002-05-12 at 14:34, Rogério Brito wrote:
>
> > > All that I can say is that I feel cheated. :-(
> >
> > Well, the actual movies shouldn't be interlaced.
>
> Well, I read that also in Ben's reply and got surprised, since
> without exception all DVDs that I have seen to this day are
> interlaced.
Sounds like bad encodings. The original movies as shown in theaters obviously
aren't interlaced so if a DVD is that's purely artificial.
> > Rumour has it that the current one in benh's tree is 2.2 except the
> > version is wrong (somebody posted a patch to 'fix' the version number to
> > linuxppc-dev), but if I were you I'd wait for confirmation from benh
> > before relying on that. :)
>
> Yes, I went to hunt that message and actually recompiled a new
> kernel with the new version, but for some reason, I couldn't
> make dri work with the X binaries from your site.
What happened? My suspicion is that the other guy only tried with the 4.2 3D
driver, where 2.1 or 2.2 doesn't really make a difference.
> > > Perhaps the r128 module isn't being maintained?
> >
> > It is, kinda, by XFree86 and DRI. Both their CVS repositories have
> > the 2.2 version, just nobody has updated the Linux kernel yet.
>
> I see. I'm crossing my fingers for this update to happen
> soon. :-)
It's being worked on, see the dri-devel archives if you're interested.
Meanwhile, for 4.2 you can build the DRM from the XFree86 4.2 CVS branch or
from http://xfree86.org/~alanh/ .
> > > What is the problem with publishing the interfaces for that? I
> > > thought that ATI were an open-source friendly company. :-(
> >
> > They are IMHO. Every company seems to be afraid of releasing that
> > kind of information, I have an idea why but people tell me there's
> > no reason...
>
> Could you say what could be the possible reasons for ATI to
> not release the specifications? I'd be really interested to
> know. I promise that I won't start a flamewar if I don't like
> what I read. :-)
My idea is it has to do with certain US laws, but what do I know.
> But how "closed" is ATI to specifying the interface to hw
> accel of their chips?
They provide docs to interested developers, just not for these features.
> Perhaps an organized petition would help here?
Who knows, but I'd expect the GATOS project to have achieved something in
that case.
> > I'm afraid you'll be disappointed. Seems it was only good for a real
> > 'gain' as a hack on top of 4.1. Now that it's done (more :)
> > correctly, a lot of cycles are still wasted waiting for the DMA
> > transfer to complete.
>
> Well, just using a new X helped performance a bit with xine. I
> am hoping that DMA would help more. Any tiny bit would help.
>
> And is the CPU stalled when the DMA transfer is being
> performed? I'd say no, given my limited understanding of the
> matter (otherwise, there would be not improvement in doing DMA
> in the first place, right?)
Right, but with a catch: the DMA transfer must complete before the image can
displayed. Right now, this is ensured by waiting for the DMA engine to go idle,
which is basically implemented as a busy loop in the DRM. So while the transfer
will be faster than with plain memcpy, a lot of CPU cycles are wasted.
> If it is not, then even lowering the CPU consumption would
> help, as there could be more processes decoding the video,
> right? Or would the actual video output be slower, in general?
Should be at least as fast, just hardly significantly faster yet.
> OTOH, perhaps the bottleneck being how the video operations
> are slower may be the reason why mplayer's video out benchmark
> with X 4.2 was so much higher than with X 4.1?
I don't understand. What does that benchmark measure and how do the results
compare?
> > Using an interrupt might help there.
>
> I don't understand this, sorry. :-)
The chip could issue an interrupt when the DMA transfer is complete so
the CPU could do something useful while it's in progress.
--
Earthling Michel Dänzer (MrCooper)/ Debian GNU/Linux (powerpc) developer
XFree86 and DRI project member / CS student, Free Software enthusiast
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