Subject: Re: [linux-audio-dev] Linux Alsa Audio over 1394 - a Thesis
From: Steve Harris (S.W.Harris_AT_ecs.soton.ac.uk)
Date: Wed Feb 26 2003 - 17:00:29 EET
On Wed, Feb 26, 2003 at 01:51:41 +0100, Martijn Sipkema wrote:
> Well, I'll shut up about it. I still think it is a mistake. I haven't heard
> any
> convincing (to me) arguments why an application should not handle variable
> sized callbacks.
Because it makes certain types of processing viable, which they are not
really in variable block systems (eg. LADSPA, VST). Have a look at an
phase vocoder implementation in LADSPA (e.g.
http://plugin.org.uk/ladspa-swh/pitch_scale_1193.xml) or VST and see how
nasty and inefficient they are.
Conversly we haven't heard any convincing arguments about why we should
have variable block sizes ;) I don't think that allowing (some?) USB
devices to run with less latency counteracts the cost to block processing
algorithms.
> VST process() is variable size I think as are EASI xfer
> callbacks, but clearly JACK needs constant callbacks and there is nothing
> I can do about that...
I wouldn't hold up VST as a good example, it has many design flaws IMHO.
As Paul pointed out VST and LADSPA require variable sized blocks becuase
they have no event system. I dont know what EASI xfer is. Its not JACK
that needs the fixed sizes, its that applications, JACK itsself couldn't
care less.
- Steve
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