# The MIDIMonster

Named for it's scary math, the MIDIMonster is a universal translation
tool between multi-channel absolute-value-based control and/or bus protocols,
such as MIDI, DMX/ArtNet and OSC.

It allows the user to translate channels on one protocol into channels on another
(or the same) protocol, eg

* Translate MIDI Control Changes into Notes
* Translate MIDI Notes into ArtNet
* Translate OSC messages into MIDI
* Use an OSC app as a simple lighting controller via ArtNet

## Usage

The MIDImonster takes as it's first argument the name of an optional configuration file
to use (`monster.cfg` is used as default if none is specified). The configuration
file syntax is explained in the next section.

## Configuration

Each protocol supported by MIDIMonster is implemented by a *backend*, which takes
global protocol-specific options and provides *instance*s, which can be configured further.

The configuration is stored in a file with a format very similar to the common
INI file format. A section is started by a header in `[]` braces, followed by
lines of the form `option = value`.

Lines starting with a semicolon are treated as comments and ignored. Inline comments
are not currently supported.

A configuration section may either be a *backend configuration* section, started by
`[backend <backend-name>]`, an *instance configuration* section, started by
`[<backend-name> <instance-name>]` or a *mapping* section started by `[map]`.

The `[map]` section consists of lines of channel-to-channel assignments, reading like

```
instance.channel-a < instance.channel-b
instance.channel-a > instance.channel-b
instance.channel-c <> instance.channel-d
```

The first line above maps any event originating from `instance.channel-b` to be output
on `instance.channel-a` (right-to-left mapping).

The second line makes that mapping a bi-directional mapping, so both of those channels
output eachothers events.

The last line is a shorter way to create a bi-directional mapping.

An example configuration file can be found in [unifest-17.cfg](unifest-17.cfg).

## Backend documentation
This section documents the configuration options supported by the various backends.

### The `artnet` backend

The ArtNet backend provides read-write access to the UDP-based ArtNet protocol for lighting
fixture control.

#### Global configuration

| Option	| Example value		| Default value 	| Description		|
|---------------|-----------------------|-----------------------|-----------------------|
| `bind`	| `127.0.0.1 6454`	| *none*		| What address and port to bind the ArtNet socket to |
| `net`		| `0`			| `0`			| The default net to use |

#### Instance configuration

| Option	| Example value		| Default value 	| Description		|
|---------------|-----------------------|-----------------------|-----------------------|
| `net`		| `0`			| `0`			| ArtNet net to use	|
| `uni`		| `0`			| `0`			| ArtNet universe to use|
| `output`	| `true`		| `false`		| Controls whether ArtNet frames for this universe are output (otherwise the universe is input-only) |
| `dest`	| `10.2.2.2`		| `255.255.255.255`	| Destination address for sent ArtNet frames |

#### Channel specification

A channel is specified by it's universe index. Channel indices start at 1 and end at 512.

Example mapping:
```
net1.231 < net2.123
```

#### Known bugs / problems

Currently, no keep-alive frames are sent and the minimum inter-frame-time is disregarded.

### The `midi` backend

The MIDI backend provides read-write access to the MIDI protocol via virtual ports.

#### Global configuration

| Option	| Example value		| Default value 	| Description		|
|---------------|-----------------------|-----------------------|-----------------------|
| `name`	| `MIDIMonster`		| none			| MIDI client name	|

#### Instance configuration

| Option	| Example value		| Default value 	| Description		|
|---------------|-----------------------|-----------------------|-----------------------|
| `read`	| `20:0`		| none			| MIDI device to connect for input |
| `write`	| `DeviceName`		| none			| MIDI device to connect for output |

MIDI device names may either be `client:port` portnames or prefixes of MIDI device names.
Run `aconnect -i` to list input ports and `aconnect -o` to list output ports.

Each instance also provides a virtual port, so MIDI devices can also be connected with `aconnect <sender> <receiver>`.

#### Channel specification

The MIDI backend supports multiple channel types

* `cc` - Control Changes
* `note` - Note On/Off messages
* `nrpn` - NRPNs (not yet implemented)

A channel is specified using `<type><channel>.<index>`.

Example mapping:
```
midi1.cc0.9 > midi2.note1.4
```
#### Known bugs / problems

Currently, no Note Off messages are sent (instead, Note On messages with a velocity of 0 are
generated, which amount to the same thing according to the spec). This may be implemented as
a configuration option at a later time.

NRPNs are not yet fully implemented, though rudimentary support is in the codebase.

The channel specification syntax is currently a bit clunky.

### The `loopback` backend

This backend allows the user to create logical mapping channels, for example to exchange triggering
channels easier later. All events that are input are immediately output again on the same channel.

#### Global configuration

All global configuration is ignored.

#### Instance configuration

All instance configuration is ignored

#### Channel specification

A channel may have any string for a name.

Example mapping:
```
loop.foo < loop.bar123
```

#### Known bugs / problems

It is possible to configure loops using this backend. Triggering a loop
will create a deadlock, preventing any other backends from generating events.
Be careful with bidirectional channel mappings, as any input will be immediately
output to the same channel again.

### 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

This backend does not take any global configuration.

#### 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 |
| `dest`	| `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 in the instance configuration using an assignment of the syntax

```
/local/osc/path = <format> <min> <max> <min> <max> ...
```

The OSC path to be configured must only be the local part (omitting a configured instance root).
**<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
```

#### 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

Ping requests are not yet answered. There may be some problems using broadcast output and input.

## Building

This section will explain how to build the provided sources to be able to run
`midimonster`.

### Prerequisites

In order to build the MIDIMonster, you'll need some libraries that provide
support for the protocols to translate.

* libasound2-dev (for the MIDI backend)
* A C compiler
* GNUmake

### Build

Just running `make` in the source directory should do the trick.

## Development

The architecture is split into the `midimonster` core, handling mapping
and resource management, and the backends, which are shared objects loaded
at start time, which provide a protocol mapping to instances / channels.

The API and structures are more-or-less documented in [midimonster.h](midimonster.h),
more detailed documentation may follow.