[PD] Which Linux distribution are you using?
Raphael Raccuia
rafael.raccuia at blindekinder.com
Wed Nov 17 10:51:25 CET 2010
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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