19 Sep
2010
19 Sep
'10
7:23 a.m.
On 09/19/2010 06:17 AM, Jonathan E. Brickman wrote:
I was reading here:
http://bpmdj.yellowcouch.org/jack.html
and became intrigued. A few questions. I would love to be able to run
with (say) three ordinary USB2 audio-in ports plus my AudioTrak Prodigy
HD2.
1. Can different jackd instances, connect and talk to each other? If I
run four instances of Jackd and qjackctl under four different names, can
I connect them all?
No. but you can connect multiple soundcards to one jackd instance using
alsa_in and alsa_out. Note however, that alsa_in/out does resample
(unless the soundcards involved are synchronized by word-clock) and you
loose sound-quality.
(FWIW you can use netjack to connect two or more jackd instances - but
then you still need alsa_in/out because the netjack slaves do not
connect to an underlying audio-device but connect to the master-jack.)
2. In the example at the web page linked above, an
"ALSA multi" device
is shown, combining multiple devices into one ALSA virtual device. If
memory and CPU is not an issue, will doing this with one Jackd instance
work better than four interconnected Jackd instances? It seems to me
that this would require a "lowest common denominator" approach to
latency-related settings, and combining PCI and USB strikes me as
possibly troublesome because of the very different needs involved.
J.E.B.
AFAIK alsa-multi devices only makes sense for soundcards that can be
chained.
It is possible to combine different devices on ALSA level but you'll
most likely get a mess: Different latencies, buffer-sizes etc and
experience drop-outs if the cards are not synchronized.
YMMV. It may not matter to you if you use the 2nd soundcard only for
telephoning or some similar task where you don't care.. but your time is
spend better buying a decent soundcard with enough I/O :)
best,
robin