Tag: audio

Updates to audiograph for iOS 6


Today I’m attempting to update audiograph to run under the current iOS/xcode releases. Here are some helpful solutions to resolving compilation errors and warnings…

(update) Had problems with git, because I forgot to pull the changes from Michael Tyson, down from github before I made changes to the files locally and committed them.

Ended up doing a wholesale copy and a lot of duplicated effort – anyway it seems to work now.

Very important: The current local version of audiograph is in tkzic/coreaudio/audiograph

I have also submitted a new version 1.1 to app store. but its in the same folder I just mentioned.

runtime view controller error:
<code>'A view can only be associated with at most one view controller at a time!</code>


group table view default color warning:


deprecated AvAudioSession methods (iOS 6.0)

I commented these out and added the updated methods

see this link for setDelegate




see Apple docs for everything else

The ‘play’ button on the bottom toolbar didn’t work on the 5g ipod touch (with taller screen)

Here’s what fixed it (in applicationDidFinishLaunching…)

from this stack overflow post: http://stackoverflow.com/questions/12395200/how-to-develop-or-migrate-apps-for-iphone-5-screen-resolution

The only really required thing to do is to add a launch image named “Default-568h@2x.png” to the app resources, and in general case (if you’re lucky enough) the app will work correctly.

In case the app does not handle touch events, then make sure that the key window has the proper size. The workaround is to set the proper frame:

<code>[window setFrame:[[UIScreen mainScreen] bounds]]</code>

There are other issues not related to screen size when migrating to iOS 6. Read iOS 6.0 Release Notesfor details.

Raspberry-Pi FX pedal

Running in Pure Data

(update) Tried this with guitarist John Drew today (2/26/2012). We ran the guitar directly into the iMic (switched to microphone, not line) and the output of iMic into an amplifier. The R-Pi was plugged into to wifi router with an Ethernet cable, so we could use touchOsc to control the delay parameters. It sounded great.

We talked about the possibility of making this into a ‘product’. One idea would be to ditch the Osc controls and build a simple hardware interface – some encoders, switches, and LED’s. You could map everything in PD and download new patches using an ethernet cable or a usb wifi connection – or even some kind of serial/usb link.

Yesterday I programmed a simple variable delay effect in pd to run on Raspberry-Pi. Control was using touchOSC as described in previous posts. I ran the effect in mono at 32k sampling rate – and it sounded great. Also its using the Griffin iMic for sound.

Here’s the command line to set the sample rate and number of channels:

pd-extended -r 32000 -nogui -channels 1 delay-effect-osc.pd


Local files:




FM Midi Synthesizer with Pd on Raspberry Pi

Here’s a simple FM Midi synthesizer developed in pd running on a Raspberry Pi. The patch was written and tested on a Macbook, then the patch file is uploaded to RPi and run using pd-extended from the command line. For example the command to run this patch is:

pd-extended -nogui -noadc -midiindev 1 piSynth1.pd

[todo: upload patch to this site. Currently in tkzic/rpi/pd/piSynth1.pd]

[udpate]: when trying this again, a few problems came up:

  1. R-Pi didn’t recognize sound card/midi: Solution was to connect the sound card directly to the R-Pi USB port and connect the Midi controller via powered USB hub
  2. Sometimes pd-extended errors out with a device busy message. Seems to run ok if you press ctrl-c and repeat the pd-extended command line. I think this problem may be due to a previous process hanging – and not exiting cleanly




Raspberry Pi with Pd: audio test


In an audio pass-through test using Pd, with a USB sound card (Griffin iMic), the maximum stereo sample rate before ‘breakup’ is 32000.In mono, it sounds “ok” at 44100. Latency seems low enough to use for music but I’m too sleepy to figure out the numbers.

I don’t know enough about Linux audio to say if the performance deficit is due to ALSA drivers, the sound card, background processes, pd, the CPU, or what?Anyway I ‘m guessing R-Pi will spawn interesting synths and lo-fi FX processors. They’re cheap enough you could use them in parallel.

Prediction: They’ll double the speed, and sell a million more by the end of the year. We’ll see a range of ‘Pi’ clones which run the same Linux distributions, but offer various speeds and IO options. It feels like the democratization of manufacturing has taken another huge leap.

pd-extended on Raspberry Pi


Using installation instructions from Pd site:


Installation worked fine. I tried running the GUI under xterm and it was a disaster. Then, using this post, I was able to get a test patch (sine wave with LFO) running in terminal mode:


Note: I changed the actual command to this due to the fact I’m running pd-extended and a USB sound card:

pd-extended -nogui -noadc testPatch.pd

This post from same source has instructions for installing pd-extended (disaster) but a very nice version of the test patch called testPatchExtended.pd


(another update) running Midi:

To run midi you need to specify the device on the command line. First I plugged in the m-audio key station 49 and rebooted RPi

To get a list of devices use:

pd-extended -nogui -listdev

Then to run a patch with midi

pd-extended -nogui -noadc -midiindev 1 testMidi.pd

Here is a page with more information on command line options


(another update) Testing with Griffin iMic. Bad news when doing an ADC->DAC passthrough, sample rates above 32000 don’t work in stereo. However 44100 and 48000 sound fine in mono.

At the higher rates in stereo, the audio breaks up. Oh well. Need to try the Behringer audio box, but I’m assuming there will be no difference. Only possibility would be to somehow devote more system resources to audio.

Raspberry Pi sound cards



A post about installing USB sound cards


And another – with better detail



Griffin imic with PD




Raspberry Pi running Pure Data

example video


PD extended…


and this update


Running PD on a headless RP


Here’s a comprehensive install script for PD-extendended from 9/2012


and another