Ian Smith smithi at nimnet.asn.au
Sat May 18 07:22:44 UTC 2013

On Fri, 17 May 2013 08:04:14 -0700, Sean Bruno wrote:
 > I'm working on a port of IDJC, which requires jackd.
 > At this point, I'm stuck on two jackd related issues.
 > 1.  How do I configure freebsd+jackd for realtime audio?  Currently I
 > have to configure my .jackdrc to disable realtime audio, e.g.
 > /usr/local/bin/jackd -r -T -d oss 

Just wondering what problems are evident running it without rtprio?  I 
gather -r with no value gives 48000, how many consumers?  Just that even 
on an old 2GHz P4 on debian 4, we found no real issues running without 
-R that tuning buffer sizes etc wouldn't fix; FM pre-transmitter feeding 
an audio logging task (darkice to mp3 VBR -q0 @ ~210kbps) and our stream 
feed (patched edcast_jack to mp3 VBR -q2 @ ~192kbps)  ALSA, though.

That said, we wound up using -R anyway (both consumers running as root) 
but it made no noticeable difference with that load: /etc/default/jackd
OPTIONS="-R -m -d alsa -d hw:0 -C hw:0 -r 44100 -n 3 -p 4096"

16483 root      15   0 41252 3456 1580 S  8.2  0.7 173:15.30 edcast_jack
 3032 root      15   0 25752 3576 1940 S  7.4  0.7   2583:03 darklogger
 3002 root      22   0 37740 3612 3312 S  0.2  0.7  44:29.66 jackd
 1491 root      25  10  2232 1140  864 R  0.2  0.2   0:00.96 top

Re what Diane said, that seems also to be the case on linux, though I 
know nothing about our jackd port or what can be done here on FreeBSD.

       -R, --realtime
              Use realtime scheduling.  This is needed for reliable 
 low-latency performance.   On  most  systems,  it
              requires jackd to run with special scheduler and memory 
 allocation privileges, which may be obtained in
              several ways.  The simplest, and least-secure method is to 
 run jackd with root privileges.  This  means
              that all JACK clients must also run as root.  With a Linux 
 2.6 kernel, ordinary users can run jackd and
              its clients using options of the realtime LSM.  Linux  2.4  
 kernels  need  "POSIX  draft  capabilities"
              enabled  (see the <linux/capability.h> include file).  
 Using that method, ordinary users who invoke the
              daemon  using  jackstart,  can  later  launch  JACK  
 clients  without  running  them  as   root.    See
              http://jackit.sourceforge.net/docs/faq.php#a52 for more 

 > 2.  Any clues on getting the microphone working with jackd?  My
 > microphones work fine under audacity, but I don't seem to be able to get
 > any audio from microphones.
 > Sean

No idea sorry, and while interested, sadly no time to play with these:

 > http://people.freebsd.org/~sbruno/idjc/
 > http://people.freebsd.org/~sbruno/shoud-idjc/

404.  http://people.freebsd.org/~sbruno/shout-idjc/ works :)

cheers, Ian

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