Open Sound Control utilities for node.js
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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.


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

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

npm test
npm run-script coverage

For the browser

If you want to use this library in a browser, you can build a browserified file (build/osc-min.js) with

npm install
npm run-script browserify

Examples

A simple OSC printer;

sock = udp.createSocket("udp4", function(msg, rinfo) {
  var error, error1;
  try {
    return console.log(osc.fromBuffer(msg));
  } catch (error1) {
    error = error1;
    return console.log("invalid OSC packet");
  }
});

sock.bind(inport);

Send a bunch of args every two seconds;

sendHeartbeat = function() {
  var buf;
  buf = osc.toBuffer({
    address: "/heartbeat",
    args: [
      12, "sttttring", new Buffer("beat"), {
        type: "integer",
        value: 7
      }
    ]
  });
  return udp.send(buf, 0, buf.length, outport, "localhost");
};

setInterval(sendHeartbeat, 2000);

A simple OSC redirecter;

sock = udp.createSocket("udp4", function(msg, rinfo) {
  var error, error1, redirected;
  try {
    redirected = osc.applyAddressTransform(msg, function(address) {
      return "/redirect" + address;
    });
    return sock.send(redirected, 0, redirected.length, outport, "localhost");
  } catch (error1) {
    error = error1;
    return console.log("error redirecting: " + error);
  }
});

sock.bind(inport);

more examples are available in the examples/ directory.


Exported functions


.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.


.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.

See "JavaScript representations of the OSC types" below.


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

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


.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.

.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.


.timetagToDate(ntpTimeTag)

Convert a timetag array to a JavaScript Date object in your local timezone.

Received OSC bundles converted with fromBuffer will have a timetag array: [secondsSince1970, fractionalSeconds] This utility is useful for logging. Accuracy is reduced to milliseconds.


.dateToTimetag(date)

Convert a JavaScript Date to a NTP timetag array [secondsSince1970, fractionalSeconds].

toBuffer already accepts Dates for timetags so you might not need this function. If you need to schedule bundles with finer than millisecond accuracy then you could use this to help assemble the NTP array.


.timetagToTimestamp(timeTag)

Convert a timetag array to the number of seconds since the UNIX epoch.


.timestampToTimetag(timeStamp)

Convert a number of seconds since the UNIX epoch to a timetag array.


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"
            args : [arg1,arg2]
        }
    

    Where args is an array of OSC Arguments. oscType is optional. args 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
    • array - array of OSC Arguments

    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, array or blob, depending on its javascript type (String, Number, Array, Buffer, respectively)

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

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

    oscType "bundle"

    timetag is one of:

    • null - meaning now, the current time. By the time the bundle is received it will too late and depending on the receiver may be discarded or you may be scolded for being late.
    • number - relative seconds from now with millisecond accuracy.
    • Date - a JavaScript Date object in your local time zone. OSC timetags use UTC timezone, so do not try to adjust for timezones, this is not needed.
    • Array - [numberOfSecondsSince1900, fractionalSeconds] Both values are numbers. This gives full timing accuracy of 1/(2^32) seconds.

elements is an Array of either OSC Message or OSC Bundle


License

Licensed under the terms found in COPYING (zlib license)