[PD] Options for Pd on Raspberry Pi (was: Textual pd primer)

[Michael Zacherl]

On 17.8.2012, at 11:03 , Duncan Speakman wrote:

> You need to have
> installed Xcode on your mac,

why would you need that?

> then use X11

X11 is an application which can be found under "Optional Installs" of the Mac OS X system disk.
Just start "Optional Installs.mpkg" and select X11.
At least I can say that for OS X versions 10.5 - 10.6.8

If that's not the case get it from here: http://xquartz.macosforge.org/trac/wiki/WikiStart
It's the software Apple bundled and it's more up to date anyway.

> and then log in as Andy
> describes.  You can then run it just by typing pd, but don't forget
> your flags! we're currently using
> pd -alsa -nomidi -audiobuf 25 -r 22050 -blocksize 128
> Tweaking all these will help!
> 
> - The gui can be pretty slow this way so I generally build the patches
> on my mac locally, then copy them over to see how the processor on the
> Gumstix handles them.

Actually on the RPi the GUI is quite ok!
In fact I found myself altering patches (for tests) on the RPi and then need to copy 
back the improved patches and abstractions to my library on the Mac.
I still don't have any HDMI hardware, so I just can check that elsewhere.
Yesterday I loaded some of the bigger patches using the RPi standalone using an HDMI screen
and editing was quite fine.
In reality a performance test running the patch under it's real conditions is inevitable anyway!
The system load changes in any case, regardless wether it's via remote or natively controlled.
The only annoying thing is the noise the audio output (analogue as via HDMI) generates when
moving mouse, windows etc. 
According to Miller it might have to do with priorities. (see below)
Also, running that via X11 has other implications:
GEM does work with X11 on the Mac since the GLX is available, where as (currently) it doesn't natively.
Consider network traffic as a load to the RPi! Fast changing gui-elements slow down this little machine!

> - couple of bugs we found when trying to run pd with -nogui
> 1. tables and delread objects behave badly unless you delay turning on
> the dsp. So in the patch that opens with no gui put a 1 or sec delay
> after a loadbang to turn on the dsp.

I ran into such a thing and apparently it's not just on this platform.
http://lists.puredata.info/pipermail/pd-list/2012-08/097279.html

> 2. (this is the really weird one) The expr object doesn't work if we
> launch Pd on startup ( init.d ) with nogui, BUT if we run it with
> -nogui in a command line over SSH it does.

on the RPi or Gumstix? As James pointed out, it may be a permission problem, 
or maybe an environment problem.

> - we're running a custom build of Ubuntu, we had to do this to get the
> built in audio and outputs on the Gumstix to work. not sure how this
> is on the Pi.

Audio is different on the RPi. HDMI is fine, analogue is a pain.
As Pierre pointed out recently it's just a simple filtered PWM output, just good enough to recognise the signal.

I'd be very interested to get a simple USB Audio-dongle working, since there's also no audio input available,
this could solve some issues (and potentially raise others).

Michael.


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