Fwd: Re: [linuxdc-dev] RedBoot CD booting and MPEG playback

[Adrian M. <ad...@mc...>]

----------  Forwarded Message  ----------

Subject: Re: [linuxdc-dev] RedBoot CD booting and MPEG playback
Date: Sun, 8 Dec 2002 18:47:42 +0000
From: Adrian McMenamin <ad...@mc...>
To: dav...@ia...

On Sunday 08 Dec 2002 6:19 pm, David Willmore wrote:
> > I think to get that sort of throughput you'd certainly need accelerated
> > 2-D video or else be prepared to accept frames being dropped. I and
> > others have compiled mplayer but there are two eseential problems:
> >
> > 1. Sound driver design (needs dma) eats up processor cycles for high
> > sample rate sounds meaning that the pressure is really on the video
>
> Does the DMA 'steal' cycles from the CPU?  Normally, isn't DMA supposed to
> help use less processor time?  This sounds backwards.

No, just my writing was unclear: I meant the driver really needs to use dma
 to be better (actually dma coupled with interrupts). It eats cycles now
 because it doesn't use dma. I haven't tried to write any dma code for it for
 some time, but I got nowhere when I last tried.

> > 2. Alternative sound driver design (not with dma, but less processor
> > hogging) gives better video performance, but sound clicks and repeats -
> > an accelerated 2d video driver might fix that.
>
> Ick.
>
> Are there sufficient spec's on the video to write a DRI driver or even a
> good accelerated 2D driver?  I've been following the DRI development for
> about a year, now, and they are always busy with things, but they're also
> very helpful to new people.  So, getting questions answered is easy.  They
> also have weekly meetings on Monday afternoons at 2100UTC (5:00EDT) on
> irc.freenode.net #dri-devel. Anyone interested in developing DRI or related
> software is invited to participate and all are invited to listen in. :)

The problem we have, as always, is there are no developers!

> The big thing for video playback would be what colorspaces and scaling
> ability the video chip has.  If it has a nicely scaled YUV colorspace
> ability, video playback gets a lot easier.  The DC has pretty good floating
> point, so that should help.
>
> Cheers,
> David
>
>
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