osc-min

osc-min

simple utilities for open sound control in node.js

This package provides some node.js utilities for working with OSC, a format for sound and systems control.
Here we implement the OSC 1.1 specification. OSC is a transport-independent protocol, so we don't provide any server objects, as you should be able to use OSC over any transport you like. The most common is probably udp, but tcp is not unheard of.

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Installation

The easiest way to get osc-min is through NPM. After install npm, you can install osc-min in the current directory with

npm install osc-min

If you'd rather get osc-min through github (for example, if you're forking it), you still need npm to install dependencies, which you can do with

npm install --dev

Once you've got all the dependencies you should be able to run the unit tests with

npm test
npm run-script coverage

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Examples

A simple OSC printer

sock = udp.createSocket "udp4", (msg, rinfo) ->
    try
        console.log osc.fromBuffer msg
    catch error
        console.log "invalid OSC packet"
sock.bind inport

Send a bunch of arguments every two seconds

sendHeartbeat = () ->
    buf = osc.toBuffer(
        address : "/heartbeat"
        arguments : [
            12
            "sttttring"
            new Buffer "beat"
            {type : "integer", value : 7}
        ]
    )
    
    udp.send buf, 0, buf.length, outport, "localhost"
    
setInterval sendHeartbeat, 2000

A simple OSC redirecter

sock = udp.createSocket "udp4", (msg, rinfo) ->
    try
        redirected = osc.applyAddressTransform msg, (address) -> "/redirect" + address
        sock.send(
            redirected,
            0,
            redirected.length,
            outport,
            "localhost"
        )
    catch error
        console.log "error redirecting: " + error
sock.bind inport

more examples are available in the examples/ directory.

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Exported functions

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.fromBuffer(buffer, [strict])

takes a node.js Buffer of a complete OSC Packet and outputs the javascript representation, or throws if the buffer is ill-formed.

strict is an optional parameter that makes the function fail more often.

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.toBuffer(object, [strict])

takes a OSC packet javascript representation as defined below and returns a node.js Buffer, or throws if the representation is ill-formed.

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.toBuffer(address, arguments[], [strict])

alternative syntax for above. Assumes this is an OSC Message as defined below, and arguments is an array of OSC Arguments or single OSC Argument

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.applyAddressTransform(buffer, transform)

takes a callback that takes a string and outputs a string, and applies that to the address of the message encoded in the buffer, and outputs an encoded buffer.

If the buffer encodes an OSC Bundle, this applies the function to each address in the bundle.

There's two subtle reasons you'd want to use this function rather than composing fromBuffer and toBuffer:

• Future-proofing - if the OSC message uses an argument typecode that we don't understand, calling fromBuffer will throw. The only time when applyAddressTranform might fail is if the address is malformed.
• Accuracy - javascript represents numbers as 64-bit floats, so some OSC types will not be able to be represented accurately. If accuracy is important to you, then, you should never convert the OSC message to a javascript representation.

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.applyMessageTransform(buffer, transform)

takes a function that takes and returns a javascript OSC Message representation, and applies that to each message encoded in the buffer, and outputs a new buffer with the new address.

If the buffer encodes an osc-bundle, this applies the function to each message in the bundle.

See notes above for applyAddressTransform for why you might want to use this. While this does parse and re-pack the messages, the bundle timetags are left in their accurate and prestine state.

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Javascript representations of the OSC types.

See the spec for more information on the OSC types.

• An OSC Packet is an OSC Message or an OSC Bundle.

• An OSC Message:

      {
          oscType : "message"
          address : "/address/pattern/might/have/wildcards"
          arguments : [arg1,arg2]
      }
  

  Where arguments is an array of OSC Arguments. oscType is optional. arguments can be a single element.

• An OSC Argument is represented as a javascript object with the following layout:

      {
          type : "string"
          value : "value"
      }
  

  Where the type is one of the following:

  • string - string value
  • float - numeric value
  • integer - numeric value
  • blob - node.js Buffer value
  • true - value is boolean true
  • false - value is boolean false
  • null - no value
  • bang - no value (this is the I type tag)
  • timetag - numeric value

  Note that type is always a string - i.e. "true" rather than true.

  The following non-standard types are also supported:

  • double - numeric value (encodes to a float64 value)

  For messages sent to the toBuffer function, type is optional. If the argument is not an object, it will be interpreted as either string, float, or blob, depending on its javascript type.

• An OSC Bundle is represented as a javascript object with the following layout

      {
          oscType : "bundle"
          timetag : 7
          elements : [element1, element]
      }
  

  Where the timetag is a javascript-native numeric value of the timetag, and elements is an array of either an OSC Bundle or an OSC Message The oscType field is optional, but is always returned by api functions.