Re: a joint letter on low latency and Linux

[Paul Barton-Davis]

>What "hundreds of thousand of lines"?  I think your problem is that

Lets just start with the ALSA drivers. Currently weighing in at about
145,000 lines. All of which *has* to be ported to work with RTLinux.

Then we can throw in the framebuffer drivers for the video folk, plus
the various video/tv interfaces, USB for digital audio and MIDI. 

I think that takes us to at least a couple of hundred thousand lines
which *must* be ported to RTLinux before any apps, no matter how they
are designed, can be targeted. Not quite true - most of mine are audio
only, so just doing ALSA would be fine.

>It's true that I'm not an expert in this area so my I'm completely wrong,
>educate me.  

As explained in another couple of emails, your description is true for
recording, and by corollary, its true for audio playback. But these
are not problem areas for Linux right now. Well, not if we assume that
Stephen and Rik and Andrea and Juan and the rest of the VM gang fix
streaming disk I/O :)

However, your understanding/model is not correct for FX processing,
where the results of the non-RT processing need to be written back the
audio interface. You therefore cannot afford delays in the FX
processing either, not just the sampling. This is also true of
MIDI-driven software synthesis, where incoming MIDI data needs to
result in certain audio output emerging from the audio interface
within a required and small period of time (preferably about 1ms, but
3ms will do).

>Because your approach is the same tired bag of mistakes that helped make
>other operating systems piles of sh*t.

I know this is not truly an ad hominem attack, and I know that you
feel very bitter about this, but I don't think that this kind of
language helps persuade any of us of the wisdom of your convictions.

--p