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diff --git a/backends/osc.md b/backends/osc.md new file mode 100644 index 0000000..1446e06 --- /dev/null +++ b/backends/osc.md @@ -0,0 +1,103 @@ +### The `osc` backend + +This backend offers read and write access to the Open Sound Control protocol, +spoken primarily by visual interface tools and hardware such as TouchOSC. + +#### Global configuration + +| Option | Example value | Default value | Description | +|---------------|-----------------------|-----------------------|-----------------------| +| `detect` | `on` | `off` | Output the path of all incoming OSC packets to allow for easier configuration. Any path filters configured using the `root` instance configuration options still apply. | + +#### Instance configuration + +| Option | Example value | Default value | Description | +|---------------|-----------------------|-----------------------|-----------------------| +| `root` | `/my/osc/path` | none | An OSC path prefix to be prepended to all channels | +| `bind` | `:: 8000` | none | The host and port to listen on | +| `destination` | `10.11.12.13 8001` | none | Remote address to send OSC data to. Setting this enables the instance for output. The special value `learn` causes the MIDImonster to always reply to the address the last incoming packet came from. A different remote port for responses can be forced with the syntax `learn@<port>` | + +Note that specifying an instance root speeds up matching, as packets not matching +it are ignored early in processing. + +Channels that are to be output or require a value range different from the default ranges (see below) +require special configuration, as their types and limits have to be set. + +This is done by specifying *patterns* in the instance configuration using an assignment of the syntax + +``` +/local/osc/path = <format> <min> <max> <min> <max> ... +``` + +The pattern will be matched only against the local part (that is, the path excluding any configured instance root). +Patterns may contain the following expressions (conforming to the [OSC pattern matching specification](http://opensoundcontrol.org/spec-1_0)): +* `?` matches any single legal character +* `*` matches zero or more legal characters +* A comma-separated list of strings inside curly braces `{}` matches any of the strings +* A string of characters within square brackets `[]` matches any character in the string + * Two characters with a `-` between them specify a range of characters + * An exclamation mark immediately after the opening `[` negates the meaning of the expression (ie. it matches characters not in the range) +* Any other legal character matches only itself + +**format** may be any sequence of valid OSC type characters. See below for a table of supported +OSC types. + +For each component of the path, the minimum and maximum values must be given separated by spaces. +Components may be accessed in the mapping section as detailed in the next section. + +An example configuration for transmission of an OSC message with 2 floating point components with +a range between 0.0 and 2.0 (for example, an X-Y control), would look as follows: + +``` +/1/xy1 = ff 0.0 2.0 0.0 2.0 +``` + +To configure a range of faders, an expression similar to the following line could be used + +``` +/1/fader* = f 0.0 1.0 +``` + +When matching channels against the patterns to use, the first matching pattern (in the order in which they have been configured) will be used +as configuration for that channel. + +#### Channel specification + +A channel may be any valid OSC path, to which the instance root will be prepended if +set. Multi-value controls (such as X-Y pads) are supported by appending `:n` to the path, +where `n` is the parameter index, with the first (and default) one being `0`. + +Example mapping: +``` +osc1./1/xy1:0 > osc2./1/fader1 +``` + +Note that any channel that is to be output will need to be set up in the instance +configuration. + +#### Supported types & value ranges + +OSC allows controls to have individual value ranges and supports different parameter types. +The following types are currently supported by the MIDImonster: + +* **i**: 32-bit signed integer +* **f**: 32-bit IEEE floating point +* **h**: 64-bit signed integer +* **d**: 64-bit double precision floating point + +For each type, there is a default value range which will be assumed if the channel is not otherwise +configured using the instance configuration. Values out of a channels range will be clipped. + +The default ranges are: + +* **i**: `0` to `255` +* **f**: `0.0` to `1.0` +* **h**: `0` to `1024` +* **d**: `0.0` to `1.0` + +#### Known bugs / problems + +The OSC path match currently works on the unit of characters. This may lead to some unexpected results +when matching expressions of the form `*<expr>`. + +Ping requests are not yet answered. There may be some problems using broadcast output and input. |