KDE4 MM, a view from usability and general applicaiton development

[Arnold Krille]

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 have
> > so much work to do in your process, that its _very_ likely you don't have
> > 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 apps 
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 
but then you don't get mixing (the real mixing with changing the volume 
dynamicly (Yes, I love brackets! (I am the bracket master...)))).

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

Good night,

Arnold
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