Le 17. 11. 10 03:36, Martin Schied a écrit :
On 15.11.2010 23:06, Raphael Raccuia wrote:
Le 15. 11. 10 22:21, Pierre Massat a écrit :
Hi,
I have installed Ubuntu 10.04 LTS, plus some ubuntu studio stuff
(the audio packages and the plugins). I also tried the rt-kernel. It
didn't work.
But i am amazed, blown away, baffled, etc. Because the generic
kernel does have some crazy rt capabilities indeed. I guess the
ubuntu studio packages must have created the audio group and jack
must have written the proper things in the limit file, but still, it
works surprisingly well. Jack can run in rt with a latency as low 4
ms without any xruns, although it crashes.It works just fine at 5.33
ms. Even pd itself work with an extremely low latency (I'd say below
7 ms), I'm assuming that's because it was configured to run in rt
during the install.
I don't even know if i need JACK anymore.
jack don't add latency, and it's a powerfull sound server... you can
connect pd to the outputs of your sound device and/or other
sound/midi softwares, then you can save a patchbay to recover your
patch... it's one of the most interesting stuffs on linux.
it does add latency in most cases. you specify the amount of latency
by using different period sizes and numbers of periods settings. But
you can use very small buffers on some systems with good audio
hardware, so they have the same size you would use inside pd in
standalone (64samples). In this case you will not have more latency
using jack than using pd standalone. (I'm also only 99.9% sure about
this, beware.).
From jack-audio.org
"Doesn't use JACK add latency?
There is /NO/ extra latency caused by using JACK for audio input and
output. When we say none, we mean absolutely zero. The only impact of
using JACK is a slight increase in the amount of work done by the CPU to
process a given chunk of audio, which means that in theory you could not
get 100% of the processing power that you might get it if your
application(s) used ALSA or CoreAudio directly. However, given that the
difference is less than 1%, and that your system will be unstable before
you get close to 80% of the theoretical processing power, the effect is
completely disregardable."
but of course, if you just run pd, you don't need it and you can set
latency into pd, I forgot that. I mostly interface pd with other soft (
ardour or any recorder, midi sequencer, some plugin via jack-rack or
calf etc...), and I plug midi controllers, but you can do it in qjackctl
without running jack (alsa tab in connection window)...
Practically speaking - on systems I used until now I could always
achieve lower buffer sizes using pd standalone and thus get lower
round trip delays too.
I couldn't tell by ear which config was faster, Pd alone or Pd plus
JACK.
maybe I'm wrong, but I thing only jack can provide rt...
you can run pd with the -rt flag, without jack. fo me it has proven to
be far more stable at the lowest possible latencies than using jack.
but this depends on your setup too. I don't use jack when I don't need it.
Martin
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