[PD-ot] How to massage pd into starting with Alsa on Beagleboard

Edgar Berdahl eberdahl at ccrma.Stanford.EDU
Fri Jul 16 12:15:57 CEST 2010


Hi,

I am interested in running Pd on the Beagleboard under Angstrom linux.  
For this reason, I have recompiled Pd vanilla on the Beagleboard with  
support for Alsa and jack audio. The sound drivers on the Beagleboard  
are not very good. In particular, it is reported on the Beagleboard  
lists that the audio input drivers may not currently work at all.

So I am currently trying to get Pd to work for audio output only on  
the Beagleboard. I do not see why this is a problem because I can use  
mplayer with Alsa to play a wave file out of the sound interface. With  
mplayer the sound quality is fine and CPU usage is only about 3% or  
4%. Furthermore, I can start up a jack audio server as long as I  
disable the audio inputs using -P
# /usr/bin/jackd -d alsa -d hw:0 -r 44100 -P -p 64

However, for the life of me I cannot seem to get Pd to produce sound  
output. For instance, if I try to start Pd using jack
# pd -jack -noadc test.pd &
it resets the number of channels to zero, and the CPU usage according  
to top skyrockets to about 95%. To try to start audio, I have to  
choose Media|jack, manually put a check in the box "output device 1",  
and set the channels to 2. Then Pd starts to report, "audio I/O  
stuck... closing audio".

Or, if I try to start Pd using Alsa directly using
# pd -alsa -blocksize 64 -inchannels 0 test.pd &
I get "watchdog: signaling pd..." repeatedly, top says Pd uses 95% of  
the CPU, and there are DIO errors
Or if I try
# pd -alsa -blocksize 64 -noadc test.pd &
or all sorts of other permutations, the result is essentially the  
same. It doesn't matter whether I am using "omap3beagle (hardware)" or  
"omap3beagle (plug-in)".

Does anyone have any other ideas for ways in which I might be able to  
get Pd to produce sound out like mplayer does? I have tried all the  
startup switch combos that immediately came to mind. Could there be  
some inherent reason why Pd will not work if zero audio input channels  
are available?

Thanks!

Ed
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