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Re: sound no longer works for some programs

From: Chris Turner <c.turner@xxxxxxxxxxxxxxxxxxx>
Date: Wed, 20 Oct 2010 01:51:15 -0500

Pierre Abbat wrote:
I'm installing it with pkgin, and I get this message:
NOTE:  Unfortunately, JACK wants to use a linux /proc filesystem...
It's a DFly binary; does it know to look in the emulated /proc?

ha - I think I didn't see this because I just built everything in /usr/pkgsrc/audio to see what would build..

In any event, you've inspired me to restart my testing anew -
I'm currently running the following script to start jack

(see below - non realtime, as regular user)

and indeed, it does seem like I'm able to get some stuff
from snd into the speakers (snd_hda) - and also routed
through jack-rack and a simple 'echo' delay -
(echo 'todo: port more plugins' >> todolist)

I had to tune up my shared memory tunables to make this work -
this needs to be done on a reboot - 2 entries locally are:


(which is also to accommodate pgsql - so YMMV)

There's some hefty discussion history on the linux audio list
about kernel schedulers, thread preemptability, etc in terms
of ensuring that audio latency is 'suitable' for real-time
use (e.g. playing your $instrument in time with the audio software
without having to adjust for the delay)

this in fact is a big part of what led to the soft-realtime
scheduling misc. in the 2.6 linux kernel scheduler - and also
IIRC wouldn't be possible to do on DF without heavy modifications
to system calls, etc, etc, etc -

I'm ignoring this as for now, as I'm mostly interested in sequencing,
don't have nearly enough *working* to tax the processor,
and also - all of this stuff might be less of an issue with
multi-multicore processors (which weren't at all common when
that stuff was going on) - as processor contention then becomes
less of an issue.

Anyhow - welcome to the beyond-bleeding-edge, or something..

- Chris

$ cat dojack
#! /bin/sh
echo 'starting jackd'

# check for shmget errors -
# might need to ipcrm
# fixme ipc key not 100% verified, but has been same across a few restarts

ipcrm -M $jack_shm_key;
exec jackd -d oss -r 44100

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