Hey list,

Thanks for your prompt replies and helpfulness!

I could not get qjackctl to work, the audio will not go through and the PD CPU load gets abnormally high at around 67%...
I had already played with the sample rate and I had noticed that augmenting the frequency yields better results but the noise was still very present. 
The sound card itself works correctly with Audacity so I am sure it would work with the arecord and aplay commands Brian suggested. Weirdly, it is only with PD that it is struggling...

On a more encouraging note, as Brian suggested, it seems that the problem (or one possibility) is the duplex audio. I haven't thought about using the card as an output only device before and it did work! But afterwards, I was not able to change the settings back and use the noisy duplex audio any more, I was only able to switch the output devices...

@Brian: What type of software are you using for the signal processing with the Raspberry Pi? I am very curious because I had first attempted to build this project on a BeagleBone Black but the heavy PD patches made it unstable or crash...




On Sat, Apr 5, 2014 at 12:16 PM, Brian Fay <ovaltinevortex@gmail.com> wrote:
If you haven't tried it already, try increasing the latency in the audio settings (probably not the issue, but worth a shot).

Maybe it's only having trouble with duplex audio (simultaneous input and output). Do you have both input and output enabled for your soundcard? Does it work if you only have the output device set, and leave the input device blank?

You can test to see if duplex audio is working outside of pd - try running "arecord | aplay" (the vertical bar means pipe the data from arecord into aplay), and see if you get usable sound. You may need to set some command line flags on those to get the sample rate and audio devices right, sorry I don't know them offhand.

I am running a fairly similar setup - for an honors project at my university, I'm using a Raspberry Pi and Behringer UCG102. I have a nice multi-effects pedal working at less than 20ms latency. If my Raspberry Pi can handle it, I feel like your UDOO quad should definitely be able to. I'd like to add that you have a nice taste in projects :)


On Fri, Apr 4, 2014 at 10:41 AM, Carlos Sanchez <csanchez126@gmail.com> wrote:
Yes, I have tried changing sample rates and it has not solved the issue.

The sound card I am using is basically a copy of the Behringer UCG102 guitar to USB interface : http://www.behringer.com/EN/Products/UCG102.aspx



On Fri, Apr 4, 2014 at 8:40 AM, tim vets <timvets@gmail.com> wrote:
and what is this 'Generic Guitar to USB' exactly?



2014-04-04 3:09 GMT+02:00 Carlos Sanchez <csanchez126@gmail.com>:
Hello PD-list,

I am currently working on my semester project which is a guitar multi-effect pedal using the UDOO Quad and PD. I got everything up and running on the Linaro Ubutu 12.04 LTS build provided by UDOO and I am having strange results with PD. The soundcard I am using works normally when I am using Audacity. It plays wav files and can record the guitar signal correctly but when it comes to PD, a basic osc object or a table read through ALSA produces a strange digital noise, completely ruining the audio signal.

I have also tested this setup with a M-Audio Fast Track Pro USB card and the playback worked without issues, although I could not get the input signal through the adc object for an unknown reason. 

Has anyone tried a similar setup for guitar usage?

Thanks!

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