[PD] Which Linux distribution are you using?

[Pierre Massat]

I agree that JACK doesn't seem to add any latency. The thing is, if Pd alone
and Pd + JACK end up having the same latency, I don't see why i should
bother running two programs.
Yet, I'm not sure about Pd's latency. I know that the "Delay" in Audio
settings doesn't seem to mean anything realistic at all (correct me if i'm
wrong). I can't push it below 8 ms without running into intolerable audio
drop-outs, even though JACK is able to run at a latency below 5 ms. As I
said, my ear isn't fast enough to detect any difference between both setups.
So i guess I'll just try the program that was mentioned in one of the
previous messages.

I also have another question. For now only pd vanilla is installed on my
laptop, because ubuntu studio packages don't include pd-extended (which by
the way is difficult to understand, given all the kind of useless and
sometimes redundant apps they do provide). So, say I installed pd-extended,
do you think i'll have to tweak something in order to get the same
performances as with vanilla (stuff like adding it to the audio group,
changing the rt, buffersize, etc...)?

Incidentally, Ubuntu 10.04 LTS installed very quickly and without any
particular issues. It also starts and stops in no time. The only drawback is
(as usual) that the wireless card doesn't work properly out of the box.

Thank you all for your help and advice!

Pierre

2010/11/17 Raphael Raccuia <rafael.raccuia at blindekinder.com>

>
>
> 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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