Re: [ecasound] MIDI controller latency

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Subject: Re: [ecasound] MIDI controller latency
From: Kai Vehmanen (k@eca.cx)
Date: Sun Jan 21 2001 - 23:55:02 EET


On Sun, 21 Jan 2001 bsaylor@macalester.edu wrote:

> I asked about this problem on the list before but didn't get a
> response..

It's just that you asked a difficult question... this tends to
affect the response time. ;)

> I'm using ecasound v1.8.5d15 and a recent CVS version of ALSA (however,
> I use ecasound with OSS emulation). When controlling effects parameters
> with an external MIDI controller I get a large latency (about 1 second)
[...]
> problem with ALSA, because I can use the controller in realtime with
> another program (SpiralSynth). What could be going on? Any help would

This is very difficult indeed. First of all, ecasound's current
MIDI-subsystem (module that does the actual reads from the MIDI-device)
is not very good. It's ancient code that hasn't been modified much since -
hmm - 1998-99 or so. And as I've said before, I intend to rewrite the
whole thing during 1.9.x, so fixing the old code isn't a top priority.

Anyway, even though the old code has its problems, there still
shouldn't be the kind of delays you're experiencing. Have you tried to
play around with the -b:bsize parameter (ie. also trying bigger
values)? Another thing that comes to my mind is that your controller is
outputting too much data and ecasound can't handle it. Just in case,
you could try modifying the MIDI ring-buffer size in
libecasound/eca-midi.h:

- #define MIDI_IN_QUEUE_SIZE 1024
+ #define MIDI_IN_QUEUE_SIZE 16384

... recompile and see whether this helps.

-- 
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