Robin Gareus

TSPS

rgareus — Fri, 18 May 2012 12:53:41 +0000

Toolkit for Sensing People in Spaces

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rgareus — Wed, 16 May 2012 15:16:36 +0000

Page	Date	Tags
Transom » Walter Murch	16.05.2012 15:16	Bookmark, article

Transom » Walter Murch

rgareus — Wed, 16 May 2012 15:16:05 +0000

URL: http://transom.org/?page_id=7006

DENSE CLARITY – CLEAR DENSITY

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JACKdbus - Desktop integration - backend-switching

rgareus — Wed, 09 May 2012 14:49:35 +0000

Prototype of automatic backend-switching for JACK2 using dbus.

You may know this Mac/OSX feature: one plugs or unplugs an external audio-interfaces and the system automatically switches the sound to the new device. - It may not always be what you want, but it is an very handy feature especially for mobile systems. and here's how to set this up for JACK on GNU/Linux..

Overview

First, we need a mechanism to switch the “JACK backend” in order to switch between audio-interfaces. The task includes taking care of re-connecting physical I/O ports in case they're different on each device.

Second, said mechanism needs to be triggered automatically when a new device is connected or if a device goes away. Here's a short annotated demo-video:

(If Flash is installed JavaScript is activated, you can watch a video inside this web page.)

(well yes, I should have ripped out that USB cord more visibly.. sorry, next time. I might use a real camera too, then.)

Prerequisites

recent jack2 from http://jackaudio.org ~~+ patcheset http://trac.jackaudio.org/ticket/213~~
myjackctl.sh myjackctl - or similar program to switch JACK-backends.
dbus-triggerd - or a similar tool that runs a hook-script on receiving dbus-signals.

Download:

Note: dbus-triggerd and a jack2 debian packages (source and i386) are available from

deb http://rg42.org/deb/ sid main

Installation and testing

get jack2, ~~patch,~~ compile and install (or get the debian package).
compile and install dbus-triggerd (or get the debian package).
download and install myjackctl.sh to PATH (~/bin or /usr/local/bin), chmod +x.
open a window to watch tail -f ~/.log/jack/jackdbus.log

killall -9 jackd jackdbus # clean start
jack_control eps verbose true        # tell jackdbus to be verbose
myjackctl.sh alsa hw:0 1024  48000 3 # launch jackd on first ALSA interface -p1024 -r48000 -n3
myjackctl.sh alsa hw:1               # switch to second ALSA interface

Launch some jack clients, players etc and repeat testing with myjackctl.sh.

Automating it with dbus-triggerd

dbus-triggerd is a tool to trigger shell-commands upon receiving a given dbus-signal.

It can be used to invoke myjackctl.sh in order to change the JACK-backend if

a new audio-interface is connected (system-dbus org.freedesktop.Hal.Manager,member=DeviceAdded) → use the newly connected device.
an audio-interface is disconnected (system-dbus org.freedesktop.Hal.Manager,member=DeviceRemoved) → switch to a fallback audio-interface.
JACK daemon signals device-error (session-dbus org.jackaudio.JackControl,member=DeviceError) → switch to a fallback audio-interface.

The two last are redundant and exclusive. JACKd still needs a patch to send a DeviceError. Using HAL's DeviceRemoved may be problematic for setups with more than two sound-cards if the removed device was not currently the one used by JACK.

Example to launch dbus-triggerd:

#!/bin/sh
make || exit
killall dbus-triggerd

### switch to sound 'hw:0' on any DeviceError
# This requires a patched JACK2, that sends a DeviceError
./dbus-triggerd $@ "type='signal',path=/org/jackaudio/Controller,interface=org.jackaudio.JackControl,member=DeviceError" --shell "myjackctl.sh alsa hw:0" &

# This an alternative to the above, using the HAL message
#dbus-triggerd $@ --system "type='signal',path=/org/freedesktop/Hal/Manager,interface=org.freedesktop.Hal.Manager,member=DeviceRemoved,arg0=/org/freedesktop/Hal/devices/usb_device_582_74_noserial_if0_sound_card_2" --shell "myjackctl.sh alsa hw:0" &

### switch to external USB sound device 'hw:2' when it's connected
./dbus-triggerd $@ --system "type='signal',path=/org/freedesktop/Hal/Manager,interface=org.freedesktop.Hal.Manager,member=DeviceAdded,arg0=/org/freedesktop/Hal/devices/usb_device_582_74_noserial_if0_sound_card_2" --shell "myjackctl.sh alsa hw:2" &

Implementation

Here be dragons…

The mechanism for backend-switching is implemented by a shell-script myjackctl.sh (which call dbus-send) that controls jack2d by exchanging dbus-messages.

myjackctl.sh is started with different command-line parameters on-demand by dbus-triggerd.

org.freedesktop.Hal.Manager,member=DeviceAdded
org.jackaudio.JackControl,member=DeviceError (requires patch to jack2)
(or) org.freedesktop.Hal.Manager,member=DeviceRemoved

Note that myjackctl.sh uses the org.jackaudio.PatchBay dbus-API which is broken in jack2-r4120 (see ticket below) and fixed by Nedko in jack2-r4366.

Future: Instead of patching jack2 to send additional messages (here: org.jackaudio.JackControl,member=DeviceError), the trigger functionality should be built into jackd, but requires a callback to the control API to be added to JACK.

The shell hook-script (myjackctl.sh) could be implemented easier and more flexible using python (jack-control API bindings) or similar language more suitable to parse and provide audio-port mapping and configuration.

References

audio, floss, jack, linux

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German influence on the French Election

rgareus — Sun, 06 May 2012 20:54:20 +0000

Taking a leaf out of Merkel's book, another German is trying to influence the French elections..

Last week I received a phone call by my collaborating artist and previous supervisor Maurice_Benayoun that there is interest to show a customized version of our project Emotion-Forecast during the final stages of the presidential election campaign for François_Hollande.

My first reply was: “I'm not interested in political statements. Yet the project is free-software, everyone can use and customize it for their needs.”

As citizen of the European-Internet, I am not allowed to vote in France - so here's my change to take some influence nonetheless. While I can't say that I'd vote for Mr. Hollande, I am certain that I don't want to continue living in a country ruled by Sarkozy. Decision-making by exclusion, fine.

So I spent a few hours hacking - which is fun anyway - and a few hours carefully translating English into French.. et voila. La prévisualisation est disponible en ligne.

I'm still undecided what I'd actually vote on next Sunday. Pretty much both options seem like dead-ends to me. Still, I'm happy that people's emotional-concerns are included in an election campaign, which otherwise is pretty much focused on the economic situation: jobs, taxes, dept-crisis,.. sprinkled of immigration and security concerns.

Even though this “emotional weather forecast” will likely be presented out of context of our initial intention, I very much welcome the opportunity that it may inspire some people at least.

Update: it is going to be presented on Sunday, May/6 at Place de la Bastille.

Update: article in huffingtonpost about the project[ion].

news, installation, video

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Seeing Music - devel

rgareus — Fri, 04 May 2012 09:43:15 +0000

System Architecture

The audio-processor is a black-box that analyzes incoming sounds and generates OSC messages. A basic set of messages and parameters needs to be specified (those can be extended in the future).
- volume / energy
- tempo / rhythm
- pitch / timbre
- frequency spectrum and frequency spread
- etc
- additional msg (initial and periodical updates) configuration (number of channels, samplerate, etc)
Video-generator has an internal pipeline. e.g. shape-generator, texture-overlay, zoom, filter (eg. blur, brightness/contrast), encode.
- every element in the pipeline may have configuration parameters
- these parameters are either fixed or can be modified dynamically (interact with input)
- dynamic parameters can be set by OSC (either from the sound-analyzer or via user-interaction)
- a config file or database (aka preset) describes the pipeline and defines a map of parameters.
User interaction - also sends OSC messages to the video-generator (depending on the config, these are internally forwarded to one or more elements in the pipeline)
- interaction can be via HID (mouse, keyboard, etc)
- Joystick, Wii-mote, etc
- Mixing-desk (faders or knobs)
- advanced systems such as camera → processing → OSC