[PD] Gigs with Pd

Dan Wilcox danomatika at gmail.com
Fri Jul 30 12:40:33 CEST 2010

On Jul 29, 2010, at 8:30 PM, Jeffrey Concepcion wrote:

> I would like to exclude my laptop from live performance, so to be able to upload my pd patch (or patches) to a device like the beagleboard seems perfect for my needs. 
> @Dan Wilcox - Where you able to build your setup? which one did you go for? how would you be using it (live processing, generation, or sampling,etc.?)  

I use a Xybernaut wearable computer running a minimal, no gui Ubuntu and pd with realtime priority and a Roland UA-25 soundcard. It's a slow computer (500Mhz) but with the right settings I have 2 channels in (voice and guitar) and a mixed stereo out with around 12-16ms latency, which is acceptable. The only time I get dropouts are when switching between song patches, which is not a big deal.

Pd does realtime generation and processing from control and incoming audio. A master patch contains the audio in/out, osc in/out, and playlist. An 8 channel global mixer mixes down to stereo and each song is recorded to wav as I play. Each song is a separate patch noted in the [coll] playlist text file. Switching between songs closes the current song and then opens the new one. A compact flash card contains the songs and media and a small script which is called when the cf card is mounted which tells pd which playlist to load on the card. This way I have different sets per card. The same could be done using usb thumbsticks (should be faster then cf cards) but I used cf cards since the wearable has a slot for one.

Software wise I have scripting that automatically starts everything and autoconnects alsa midi to pd. A custom daemon grabs hid gamepad events and sends them to pd over osc. The hids are automatically opened when udev detects a new hid device which is super important on a headless machine with no mouse or keyboard. I have a simple visual engine that accepts commands over osc from pd. The overhead with everything running is around 180-230 MB of RAM on a machine with only 256 but it works. I had to fiddle with getting the nice settings just right so the applications work well together.

I am currently in the process of cleaning up my setup. Once it's ready you can download and try it out on Ubuntu.

Here's my (a bit empty for now) trac project page : http://trac.robotcowboy.com/ and source repository: http://trac.robotcowboy.com/browser/robotcowboy/trunk

In the future I plan to try out a beagle board or gumstix. If I could get funding/sponsorship, I'd drop the 7 grand for one of these: http://www.bdatech.com/switchback/ a military grade UMPC. The Xybernaut I have is industrial grade (cost $10000 new, but I got for $350 on ebay) and it will outlast any netbook or consumer laptop on the road. Do not underestimate the quality and durability of the hardware you consider while building a performance machine. One option is to buy a mini-itx board and mount it and a soundcard etc into a pelican case ala AudioPint.

Also: the computer will fuck you no matter how much time you put into making it work. Make sure to have a *back up* plan for when it crashes. If you have everything setup correctly, you can just reboot and do a little song and dance ... :D My experience is that 1 reboot is enjoyed by the audience, a second is tolerated, and 3 or more means the promoter will chew you out and wonder why you don't use a Mac and Albeton etc ...

Dan Wilcox

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