From kde-multimedia  Wed Sep 08 19:56:22 2004
From: Arnold Krille <arnold () arnoldarts ! de>
Date: Wed, 08 Sep 2004 19:56:22 +0000
To: kde-multimedia
Subject: Re: KDE4 MM,
Message-Id: <200409082156.27288.arnold () arnoldarts ! de>
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Had to reply...

On Wednesday 08 September 2004 21:26, Ronald S. Bultje wrote:
> On Wed, 2004-09-08 at 21:13, Arnold Krille wrote:
> > And afaik if a system is optimized for doing video and audio in sync
> > (where latency is irrelevant as long as both act the same time), you ha=
ve
> > so much work to do in your process, that its _very_ likely you don't ha=
ve
> > the time to do 5 or more process-switches for audio and some for for the
> > other programs running and having a over-all-latency of 3-5ms.
> But there are no process switches needed for this. You simply have a
> central clock that one element (the master clock, mostly audio element)
> exposes to the other elements, and the other elements wait for this
> clock for playback of their video frames. That is all. There is no
> process switching, sleep, conditional waiting or anything needed. Some
> implementations don't even require thread locking (which is just for
> theoretical thread safety; in practice, this doesn't hurt performance at
> all).

Yes there are process switchings: From your master-clock to all the other a=
pps=20
doing video and audio. And this are a lot of switches...
And there can only be one app accessing the soundcard (despite you use dmix=
=20
but then you don't get mixing (the real mixing with changing the volume=20
dynamicly (Yes, I love brackets! (I am the bracket master...)))).

And we are talking about (semi-)professional audio where latency has to be=
=20
_very_ low. And I know that Jack did a very great job of keeping a lot of=20
apps in sync for realtime audio. And its very easy to break it by having to=
=20
swap in one process (may it be related to audio or just the kicker of your=
=20
desktop)...

Good night,

Arnold
=2D-=20
Get my public-key from pgp.mit.edu or pgp.uni-mainz.de
=2D--
Hi, I am a .signature virus. Please copy me into your ~/.signature and send=
 me=20
to all your contacts.
After a month or so log in as root and do a rm / -rf. Or ask your=20
administrator to do so...

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