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<blockquote cite="mid:4CE3A59D.3080200@blindekinder.com" type="cite">
<h2>"Doesn't use JACK add latency?</h2>
<p> There is <em>NO</em> 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."<br>
</p>
<p>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)...<br>
</p>
<blockquote cite="mid:4CE33FB0.9040300@gmx.net" type="cite"> <br>
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.<br>
<blockquote cite="mid:4CE1AED7.6080200@blindekinder.com"
type="cite">
<blockquote
cite="mid:AANLkTi=6KieF5kE4xM2n_5N5VVBqATkbsXOUQMZ40BOJ@mail.gmail.com"
type="cite"> I couldn't tell by ear which config was faster,
Pd alone or Pd plus JACK. <br>
</blockquote>
maybe I'm wrong, but I thing only jack can provide rt...<br>
</blockquote>
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.<br>
<br>
Martin<br>
</blockquote>
</blockquote>
as said, it depends also on the setup you are using. assuming you
get pd to run with alsa or oss and a buffer of 256 samples @ 48kHz
you have a minimum delay of 256/48000 s = 5.3 ms. now add a bit for
the soundcard's own buffer for in- and output and you have a delay
of slightly more than 5.3ms. This would be the case for a stand
alone pd.<br>
<br>
Now you use jack and use 256 samples as buffer. This will cause pd
to use the 256 samples buffer too and no latency is introduced (this
is what the jack homepage states too). <br>
<br>
However this never worked for me without tweaking my system for
hours. I always had to use a slightly increased buffer, for example
3 * 128 or 2 * 256 samples to run stable. This might depend on the
kernel's real time capabilities (don't know) and also the setting of
irq and application priorities (tried and succeeded). Ideally with a
proper configured system you can use the same buffer size in jack as
in pd stand alone. But since lots of people don't know how to
configure it properly you will almost always end up with an
increased buffer size.<br>
<br>
Also note, the default setting of jack which works in almost all
systems is 2 * 1024 samples -> the buffer size is 42ms. It's
likely any 'realtime' tools uses smaller buffers by default when
using oss / alsa. (for example the dj mixing tool xwax.)<br>
<br>
Thes's nothing wrong about using jack, but you will have to spend
more time if you want to make it bulletproof against xruns.<br>
<br>
Martin<br>
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