Most Faust architectures provide Open Sound Control (OSC) support (the implementation is based internally on the oscpack library by Ross Bencina). This allows applications to be remotely controlled from any OSC-capable application, programming language, or hardware device.
OSC support can be added to any Faust program (as long as the target architecture supports it: see tables below) simply by adding the
[osc:on] metadata to the standard
declare options "[osc:on]";
The following tables provides a list of Faust architectures providing OSC support.
Linux Faust Architectures with OSC Support
|Alsa||GTK, Qt, Console|
|Jack||GTK, Qt, Console|
|Netjack||GTK, Qt, Console|
OSX Faust Architectures with OSC Support
Windows Faust Architectures with OSC Support
Other Faust Architectures with OSC Support
To illustrate how OSC support works let's define a very simple noise generator with a level control (we'll call it
This example can be compiled as a standalone Jack Qt application with OSC support simply by running the following command:
faust2jaqt -osc noise.dsp
When the generated application is ran from the command line:
various information is printed in the standard output, including:
Faust OSC version 0.93 application 'noise' is running on UDP ports 5510, 5511, 5512
Hence, the OSC module makes use of three different UDP ports:
5510is the listening port number: control messages should be addressed to this port.
5511is the output port number: control messages sent by the application and answers to query messages are sent to this port.
5512is the error port number: used for asynchronous error notifications.
Note that if a
declare name "Foo"; line is present in the DSP program,
Foo will be used as the OSC root name, otherwise the DSP filename will be used instead.
These OSC parameters can be changed from the command line using one of the following options:
-port numbersets the port number used by the application to receive messages.
-outport numbersets the port number used by the application to transmit messages.
-errport numbersets the port number used by the application to transmit error messages.
-desthost hostsets the destination host for the messages sent by the application. Note that the destination address can be changed with the first incoming message: first received packet from another host sets the destination address to this host.
-xmit 0|1|2turns transmission OFF, ALL, or ALIAS (default OFF). When transmission is OFF, input elements can be controlled using their addresses or aliases (if present). When transmission is ALL, input elements can be controlled using their addresses or aliases (if present), user's actions and output elements (i.e.,
bargraph, etc.) are transmitted as OSC messages as well as aliases (if present). When transmission is ALIAS, input elements can only be controlled using their aliases, user's actions and output elements are transmitted as aliases only.
-xmitfilter pathallows to filter output messages. Note that
pathcan be a regular expression (like
./noise -xmit 1 -desthost 192.168.1.104 -outport 6000
noise with transmission mode ON, using
192.168.1.104 on port
6000 as destination.
Automatic Port Allocation
In order to address each application individually, only one application can be listening on a single port at one time. Therefore when the default incoming port 5510 is already opened by some other application, an application will automatically try increasing port numbers until it finds an available port. Let say that we start
mixer (two Faust-generated applications with OSC support) on the same machine, we'll get the following:
$ ./noise & ... Faust OSC version 0.93 application 'noise' is running on UDP ports 5510, 5511, 5512 $ ./mixer ... Faust OSC version 0.93 application 'mixer' is running on UDP ports 5513, 5511, 5512
mixer application fails to open the default incoming port
5510 because it is already opened by
noise. Therefore it tries to find an available port starting from
5513 and opens it. Please note that the two outcoming ports
5512 are shared by all running applications.
Discovering OSC Applications
oscdump from the liblo package provide a convenient mean to experiment with OSC control and potentially debug applications with OSC support.
`oscsend [hostname] [port] [address] [types] [values]`: sends OSC messages via UDP. `[types]` is a string, the letters indicates the type of the following values: `i=integer`, `f=float`, `s=string`, etc.
`oscdump [port]`: receives OSC messages via UDP and dump to standard output
Note that OSC messages can be sent from any OSC-compatible applications (e.g., PureData, Max/MSP, etc.).
In the following examples, we'll use two separate terminal windows. The first one will be used to send OSC messages to the
noise application using
oscsend. The second terminal will be used to monitor the messages sent by the application using
oscdump. Commands executed on terminal 1 will be preceded by
T1$. Messages received on terminal 2 will be preceded by
T2:. To monitor on terminal T2 the OSC messages received on UDP port 5511,
oscdump will be used:
T2$ oscdump 5511
Once set we can use the
hello message to scan UDP ports for Faust applications. For example:
T1$ oscsend localhost 5510 "/*" s hello
gives us the root message address, the network and the UDP ports used by the noise application:
T2: /noise siii "192.168.1.102" 5510 5511 5512
Discovering the OSC Interface of an Application
The OSC interface of an application (the set of OSC messages we can use to control it) can be discovered by sending the
get message to the root:
T1$ oscsend localhost 5510 /noise s get
As an answer to this OSC message, a full description is printed in terminal T2:
T2: /noise sF "xmit" #F T2: /noise ss "desthost" "127.0.0.1" T2: /noise si "outport" 5511 T2: /noise si "errport" 5512 T2: /noise/level fff 0.000000 0.000000 1.000000
The root of the OSC interface is
/noise. Transmission is OFF,
xmit is set to false. The destination host for sending messages is
127.0.0.1, the output port is
5511 and the error port is
5512. The application has only one user interface element:
/noise/level with current value
0.0, minimal value
0.0 and maximal value
Widget's OSC Address
Each widget of an application has a unique OSC address obtained by concatenating the labels of it's surrounding groups with its own label.
There are potential conflicts between widget's labels and the OSC address space. An OSC symbolic name is an ASCII string consisting of a restricted set of printable characters. Therefore to ensure compatibility spaces are replaced by underscores and some other characters (asterisk, comma, forward, question mark, open bracket, close bracket, open curly brace, close curly brace) are replaced by hyphens.
Here is as an example, a very simplified monophonic audio mixer with 4 inputs and one output. For each input we have a dmute button and a level slider:
input(v) = vgroup("input %v", *(1-checkbox("mute")) : *(vslider("level", 0, 0, 1, 0.01))); process = hgroup("mixer", par(i, 4, input(i)) :> _);
If we query this application:
T1$ oscsend localhost 5510 "/*" s get
We get a full description of its OSC interface on terminal T2:
T2: /mixer sF "xmit" #F T2: /mixer ss "desthost" "127.0.0.1" T2: /mixer si "outport" 5511 T2: /mixer si "errport" 5512 T2: /mixer/input_0/level fff 0.0000 0.0000 1.0000 T2: /mixer/input_0/mute fff 0.0000 0.0000 1.0000 T2: /mixer/input_1/level fff 0.0000 0.0000 1.0000 T2: /mixer/input_1/mute fff 0.0000 0.0000 1.0000 T2: /mixer/input_2/level fff 0.0000 0.0000 1.0000 T2: /mixer/input_2/mute fff 0.0000 0.0000 1.0000 T2: /mixer/input_3/level fff 0.0000 0.0000 1.0000 T2: /mixer/input_3/mute fff 0.0000 0.0000 1.0000
As we can see, each widget has a unique OSC address obtained by concatenating the top level group label "mixer," with the "input" group label and the widget label (see the Labels as Pathnames Section). Please, note that blank spaces are replaced by underscores and metadata are removed during this operation.
All addresses must have a common root. This is the case in our example because there is a unique horizontal group
mixer containing all widgets. If a common root is missing as in the following code:
input(v) = vgroup("input %v", *(1-checkbox("mute")) : *(vslider("level", 0, 0, 1, 0.01))); process = par(i, 4, input(i)) :> _;
then a default vertical group is automatically create by the Faust compiler using the name of the file
mix4 as label:
T2: /mix4 sF "xmit" #F T2: /mix4 ss "desthost" "127.0.0.1" T2: /mix4 si "outport" 5511 T2: /mix4 si "errport" 5512 T2: /mix4/input_0/level fff 0.0000 0.0000 1.0000 T2: /mix4/input_0/mute fff 0.0000 0.0000 1.0000 T2: /mix4/input_1/level fff 0.0000 0.0000 1.0000 T2: /mix4/input_1/mute fff 0.0000 0.0000 1.0000 T2: /mix4/input_2/level fff 0.0000 0.0000 1.0000 T2: /mix4/input_2/mute fff 0.0000 0.0000 1.0000 T2: /mix4/input_3/level fff 0.0000 0.0000 1.0000 T2: /mix4/input_3/mute fff 0.0000 0.0000 1.0000
Controlling the Application Via OSC
Any user interface element of the application can be controlled by sending one of the previously discovered messages/addresses. For example, to set the noise level of the application to
0.2 the following message can be sent:
T1$ oscsend localhost 5510 /noise/level f 0.2
If we now query
/noise/level we get, as expected, the value
T1$ oscsend localhost 5510 /noise/level s get T2: /noise/level fff 0.2000 0.0000 1.0000
Turning Transmission ON
xmit message at the root level is used to control the realtime transmission of OSC messages corresponding to user interface's actions. For example:
T1$ oscsend localhost 5510 /noise si xmit 1
turns transmission in
ALL mode. Now if we move the level slider we get a bunch of messages:
T2: /noise/level f 0.024000 T2: /noise/level f 0.032000 T2: /noise/level f 0.105000 T2: /noise/level f 0.250000 T2: /noise/level f 0.258000 T2: /noise/level f 0.185000 T2: /noise/level f 0.145000 T2: /noise/level f 0.121000 T2: /noise/level f 0.105000 T2: /noise/level f 0.008000 T2: /noise/level f 0.000000
This feature can be typically used for automation to record and replay actions on the user interface, or to remote control from one application to another. It can be turned OFF any time using:
T1$ oscsend localhost 5510 /noise si xmit 0
Use the ALIAS (
xmit = 2) mode if you need to restrict the access to your program: when the ALIAS mode is used, only aliases of input elements (sliders, buttons...) can be used to control them, and output elements (
bargraph) will only emit on their aliases.
Filtering OSC Messages
When the transmission of OSC messages is ON, all the user interface elements are sent through the OSC connection.
T2: /harpe/level f 0.024000 T2: /harpe/hand f 0.1 T2: /harpe/level f 0.024000 T2: /harpe/hand f 0.25 T2: /harpe/level f 0.024000 T2: /harpe/hand f 0.44 T2: /noise/level f 0.145000 T2: /harpe/hand f 0.78 T2: /noise/level f 0.145000 T2: /harpe/hand f 0.99
We can choose to filter unwanted parameters (or group of parameters). For example:
T1$ oscsend localhost 5510 /harpe si xmit 1 xmitfilter /harpe/level
As a result, we will receive:
T2: /harpe/hand f 0.1 T2: /harpe/hand f 0.25 T2: /harpe/hand f 0.44 T2: /harpe/hand f 0.78
To reset the filter, send:
T1$ oscsend localhost 5510 /harpe si xmit 1 xmitfilter
Using OSC Aliases
Aliases are a convenient mechanism to control a Faust application from a preexisting set of OSC messages.
Let's say we want to control our previous noise example with TouchOSC on Android. The first step is to configure the TouchOSC host to
192.168.1.102 (the host running our noise application) and outgoing port to
Then we can use
oscdump 5510 (after quitting the noise application in order to free port
5510) to visualize the OSC messages sent by TouchOSC. Let's use for that the left slider of "simple layout". Here is what we get:
T2: /1/fader1 f 0.000000 T2: /1/fader1 f 0.004975 T2: /1/fader1 f 0.004975 T2: /1/fader1 f 0.008125 T2: /1/fader1 f 0.017473 T2: /1/fader1 f 0.032499 T2: /1/fader1 f 0.051032 T2: ... T2: /1/fader1 f 0.993289 T2: /1/fader1 f 1.000000
We can associate this OSC message to the noise level slider by inserting the metadata
[osc:/1/fader1 0 1] into the slider's label:
Several osc aliases can be inserted into a single label allowing the same widget to be controlled by several OSC messages
import("stdfaust.lib"); process = no.noise*hslider("level[osc:/1/fader1 0 1]",0,0,1,0.01);
Because the range of
/1/fader1 is 0 to 1 (like the level slider), we can remove the range mapping information and write simply :
import("stdfaust.lib"); process = no.noise*hslider("level[osc:/1/fader1]",0,0,1,0.01);
TouchOSC can also send accelerometer data by enabling
Settings/Options/Accelerometer. Using again
oscdump 5510 we can visualize the messages sent by TouchOSC:
T2: ... T2: /accxyz fff -0.147842 0.019752 9.694721 T2: /accxyz fff -0.157419 0.016161 9.686341 T2: /accxyz fff -0.167594 0.012570 9.683948 T2: ...
As we can see, TouchOSC sends the x, y and z accelerometers in a single message, as a triplet of values ranging approximately from -9.81 to 9.81. In order to select the appropriate accelerometer, we need to concatenate to
/accxyz a suffix
/2. For example
/accxyz/0 will correspond to x,
/accxyz/1 to y, etc. We also need to define a mapping because the ranges are different:
import("stdfaust.lib"); process = no.noise * hslider("level[osc:/accxyz/0 0 9.81]",0,0,1,0.01);
||top left rotary knob|
||middle left rotary knob|
||bottom left rotary knob|
||bottom left push button|
||bottom center left push button|
||top center left toggle button|
||middle center left toggle button|
||center left vertical fader|
||top center right toggle button|
||middle center right toggle button|
||center right vertical toggle button|
||top right rotary knob|
||middle right rotary knob|
||bottom right rotary knob|
||bottom center right push button|
||bottom right push button|
||bottom horizontal fader|
OSC Cheat Sheet
||default listening port|
||default transmission port|
||default error port|
||alternative listening ports|
Command Line Options
||set the port number used by the application to receive messages|
||set the port number used by the application to transmit messages|
||set the port number used by the application to transmit error messages|
||set the destination host for the messages sent by the application|
||turn transmission OFF, ALL or ALIAS (default OFF)|
||filter the Faust paths at emission time|
||discover if any OSC application is listening on port port|
||query OSC interface of application listening on port port|
||query JSON description of application listening on port port|
||set transmission mode|
||get widget's value|
||set widget's value|
||alias with , mapping|
||alias with min, max clipping|
DSP with polyphonic support
When the DSP code is compiled in polyphonic mode, the generated program will create a more complex hierarchy to possibly access and control individual voices.
The following OSC messages reflect the same DSP code either compiled normally, or in polyphonic mode (only part of the OSC hierarchies are displayed here):
// Mono mode /Organ/vol f -10.0 /Organ/pan f 0.0
// Polyphonic mode /Polyphonic/Voices/Organ/pan f 0.0 /Polyphonic/Voices/Organ/vol f -10.0 ... /Polyphonic/Voice1/Organ/vol f -10.0 /Polyphonic/Voice1/Organ/pan f 0.0 ... /Polyphonic/Voice2/Organ/vol f -10.0 /Polyphonic/Voice2/Organ/pan f 0.0