[PD] audio output AND input with the Rpi?

s p sebpiq at gmail.com
Tue Oct 29 08:03:10 CET 2013


Same here ... I tried with 2 different usb interfaces, and I got no luck.
In both cases I got "some" sound input, but there is a lot of popping
sounds.


2013/10/28 Chris Jack <christopherdanieljack at gmail.com>

> Hey folks,
>
> Apologies as this post is not strictly about Pd, though Pd will be a
> crucial part of my final setup so whatever solution I find ought to work
> with Pd. Also, there is a chance the issue might lie with Pd. I just don't
> know.
>
> I'm looking for a usb bus-powered audio interface for the Rpi that can
> take a stereo input and provide stereo output *at the same time.*
> * *
> I have tried a couple different images and a couple different audio
> interfaces, to no avail. Perhaps there's something can be done with one of
> these setups to get it working?
>
> First, the Pd-LA custom Raspian (v1) image and Pd 43.2:
>
> ..with Behringer UCA202 (at 44100khz):
>
> Alsamixer picks the device up but the input section shows nothing.
>
> Pd (gui) audio preferences allows selection of the interface for both
> input and output. Output only is lovely and clean but as soon as the device
> is selected for audio input the audio quality drops horrendously (vaguely
> recognisable from the original signal)..
> ..although what gives me hope is I CAN software monitor the input (poorly)
> in 'Test Audio and MIDI' with this arrangement.
>
> ..with Behringer UCA202 (at 48000khz):
>
> Output only in Pd is poor (beating and popping sound - possibly sounds
> like a samp rate conversion issue).
> When device is selected as Pd input software monitoring is possible and
> oddly, though the result is still poor, there is effectively no drop in
> quality from having the device selected only for output and the monitored
> signal sounds drastically better than at 44100khz.
>
>
> ..with Turtle Beach Amigo II* (at 44100):
>
> Alsamixer shows both input and output and allows to change gain of both.
> If plugged in from boot and only the output is selected in Pd it works but
> with a lot of jitter. Selecting the device for input too causes a further
> drop in audio quality although again I can software monitor the input in
> 'Test Audio and MIDI'
> If plugged in after boot the OS crashes.
>
>
> The Satellite CCRMA (operating via ssh) and Pd-extended:
>
> ..with Behringer UCA202 (at 44100 and 48000):
>
> Alsamixer picks the device up but again the input section shows nothing.
>
> If I have the device plugged in from boot then I get the same behaviour
> with it as I do in Pd vanilla on the Pd-LA Raspian image, ie. software
> input monitoring but at an extremely poor quality.
>
> If I don't plug the device in from boot I see it in Pd audio prefs but get
> this:
>
> ALSA input error (snd_pcm_open): No such file or directory
>
> ALSA output error (snd_pcm_open): No such file or directory
>
> from the Pd terminal and this
>
> ALSA lib pcm_hw.c:1401:(_snd_pcm_hw_open) Invalid value for card
> ALSA lib pcm_hw.c:1401:(_snd_pcm_hw_open) Invalid value for card
> oops: ALSA cards not reported in order?
>
> from the ssh terminal.
>
>
> ..with Turtle Beach Amigo II* (at 44100khz):
>
> Alsamixer shows both input and output and allows to change gain of both.
>
> If plugged in from boot and then only output selected in Pd I get clean
> audio out. If I try to select the Turtle Beach as audio inout in Pd then Pd
> stalls indefinitely when I try to 'Test Audio and MIDI' or make anything in
> a patch.
>
> Same direct input monitoring by default.
>
> Also get
>
> ALSA input error (snd_pcm_open): Device or resource busy
>
> ALSA output error (snd_pcm_open): Device or resource busy
>
> from the Pd terminal if I don't have it plugged in from boot, though no
> message in ssh terminal.
>
> *It also appears that by default the Turtle Beach does direct input
> monitoring of some sorts, the output stage sending out a clean copy of
> whatever signal is going into the input stage whenever the device is
> plugged into a usb port. With the Pd-LA image this occurred simultaneously
> while input monitoring in Pd. I guess this is part of the design of the
> Turtle Beach, though their documentation is devoid of any useful info
> regards this. If this is the case then this ain't the sound card for me,
> though clearly some might find this a very useful feature.
>
> Just to give a bit more info about what I'm attempting: I wish to run the
> stereo input from the Turtle Beach through Pd, play with the audio signal
> using data from an accelerometer (not nearly there yet) and then send the
> audio out through the Turtle Beach's stereo output.
>
> Apologies for the essay. Hopefully my findings are useful for others and
> hopefully I can get my rig working! Help muchly appreciated. I've probably
> left out some crucial bit of info so please shout me if I have!
>
> Cheers,
> Chris Jack.
>
> Chris Jack
>
> *art/research*
> http://itsmrjack.com/
>
> *discus jockeying/sound art*
> http://soundcloud.com/itsmrjack/
>
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-- 
*Sébastien Piquemal
*
*
** *-----* @sebpiq*
 -----* *http://github.com/sebpiq*
*
 ----- http://funktion.fm
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