[PD-dev] pd on armv7 (beagleboard): crackles [SOLVED]

Damian Stewart damian.ml at frey.co.nz
Wed Aug 25 10:06:15 CEST 2010


oh, that's interesting!

i think it is audio-driver related, yes. i did some further experiments, as well as putting a bunch of printfs into the OSS drivers to see what was going on.

it seems that in the case of the OSS stuff, at least while attempting to run at 44.1khz, Pd is expecting blocking behaviour from writing to /dev/dsp. below a particular blocksize (1024) it's blocking but the audio sounds nasty. above that blocksize the blocking behaviour fails.

it's certainly not Pd's fault. in the meantime, i've made an addon for openFrameworks that embeds the Pd engine in an oF application, and it seems to work just fine on the beagleboard, given sufficient audio buffering: 
http://github.com/damiannz/ofxPd

thanks
d

On 25 Aug 2010, at 03:40, Edgar Berdahl wrote:

> Hi,
> 
> Now I am able to repeat what you did. In my .pdsettings file, I use
> flags: -oss -r 8000 -audiobuf 10 -inchannels 0 -blocksize 1024 -outchannels 2
> 
> As far as I can tell, it only works for the sampling rate fs=8kHz. For example, if I use -r 16000 instead (or other faster rates), then pd still runs at 8kHz. In order to compensate, pd does weird things like counting ms only half as fast (i.e. "metro 1000" behaves like "metro 2000" normally would behave), and osc~ produces output at half the frequency specified, etc.
> 
> Do you all agree that this is a problem with the drivers for audio on the Beagleboard and not with pd? (Although mplayer and mpg123 can use the ALSA drivers just fine apparently running at normal sampling rates, pd doesn't seem to work at all with ALSA, and neither does the version of chuck that I got using "apt-get install chuck".)
> 
> 
> Thanks,
> 
> Ed
> 
> PS. BTW, in contrast with your wiki, I didn't have to modprobe snd-pcm-oss, but I did have to
> sudo apt-get install alsa-utils
> sudo apt-get install mpg123
> 
>> done: http://puredata.info/docs/developer/BuildingPdForBeagleboard
>> 
>> :-)
>> 
>> On 27 Jul 2010, at 15:49, Dan Wilcox wrote:
>> 
>> Great news. Is there a page on the puredata.info wiki on the Beagle board yet?
>> If not, can add you install steps to it, or at least notes on getting the audio
>> to work with pd?
>> 
>> I wonder why alsa has troubles ... when using oss, can you still use alsa midi?
>> I have thought of trying a beagle board but no midi would be a deal breaker for
>> me
>> 
>> On Jul 27, 2010, at 1:48 PM, Damian Stewart wrote:
>> 
>> hi all,
>> 
>> i fixed my issues with Pd on my Beagleboard running Ubuntu. the solution (thanks
>> to Julian Oliver's help) was to load the oss module (sudo modprobe snd-pcm-oss)
>> then run pd using the oss driver (pd -oss), and it sounds just lovely.
>> 
>> thanks for the other help nonetheless!
>> 
>> cheers, damian
>> 
>> -- damian stewart . @damiannz . dam... at frey.co.nz frey . contemporary art . http://www.frey.co.nz
>> 
>> 
>> -------- Dan Wilcox danomatika.com robotcowboy.com
>> 
>> -- damian stewart . @damiannz . dam... at frey.co.nz frey . contemporary art . http://www.frey.co.nz
>> 
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--
damian stewart . @damiannz .  damian at frey.co.nz
frey . contemporary art . http://www.frey.co.nz




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