transcoding

Media transcoding and streaming support

npm install transcoding
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node-transcoding -- Media transcoding and streaming for node.js

node-transcoding is a library for enabling both offline and real-time media transcoding. In addition to enabling the manipulation of the input media, utilities are provided to ease serving of the output.

Currently supported features:

  • Nothing!

Coming soon (maybe):

  • Everything!

Quickstart

npm install transcoding
node
> var transcoding = require('transcoding');
> transcoding.process('input.flv', 'output.m4v',
    transcoding.profiles.APPLE_TV_2, function(err, sourceInfo, targetInfo) {
      console.log('completed!');
    });

Installation

With npm:

npm install transcoding

From source:

cd ~
git clone https://benvanik@github.com/benvanik/node-transcoding.git
npm link node-transcoding/

Dependencies

node-transcoding requires ffmpeg and its libraries avformat and avcodec. Make sure it's installed and on your path. It must be compiled with libx264 to support most output - note that some distributions don't include this and you may have to compile it yourself. Annoying, I know.

Source

./configure \
    --enable-gpl --enable-nonfree --enable-pthreads \
    --enable-libfaac --enable-libfaad --enable-libmp3lame \
    --enable-libx264
sudo make install

Mac OS X

The easiest way to get ffmpeg is via MacPorts. Install it if needed and run the following from the command line:

sudo port install ffmpeg +gpl +lame +x264 +xvid

You may also need to add the MacPorts paths to your ~./profile:

export C_INCLUDE_PATH=$C_INCLUDE_PATH:/opt/local/include/
export CPLUS_INCLUDE_PATH=$CPLUS_INCLUDE_PATH:/opt/local/include/
export LIBRARY_PATH=$LIBRARY_PATH:/opt/local/lib/

FreeBSD

sudo pkg_add ffmpeg

Linux

# HAHA YEAH RIGHT GOOD LUCK >_>
sudo apt-get install ffmpeg

API

Sources/targets

All APIs take a source and target. Today these must be file paths that can be accessed by normal filesystem APIs. In the future they can be node streams, or in the case of sources HTTP or any other protocol node can open.

Media Information

Whenever 'info' is used, it refers to a MediaInfo object that looks something like this:

{
  container: 'flv',
  duration: 126,         // seconds
  start: 0,              // seconds
  bitrate: 818000,       // bits/sec
  streams: [
    {
      type: 'video',
      codec: 'h264',
      profile: 'Main',
      profileId: 77,
      profileLevel: 30,
      resolution: { width: 640, height: 360 },
      bitrate: 686000,
      fps: 29.97
    }, {
      type: 'audio',
      language: 'eng',
      codec: 'aac',
      sampleRate: 44100, // Hz
      channels: 2,
      bitrate: 131000
    }
  ]
}

Note that many of these fields are optional, such as bitrate, language, profile information, and even fps/duration. Don't go using the values without checking for undefined first.

Querying Media Information

To quickly query media information (duration, codecs used, etc) use the queryInfo API:

var transcoding = require('transcoding');
transcoding.queryInfo(source, function(err, info) {
  // Completed
});

Transcoding Profiles

Transcoding requires a ton of parameters to get the best results. It's a pain in the ass. So what's exposed right now is a profile set that tries to set the best options for you. Pick your profile and pass it into the transcoding APIs.

var transcoding = require('transcoding');
for (var profileName in transcoding.profiles) {
  var profile = transcoding.profiles[profileName];
  console.log(profileName + ':' + util.inspect(profile));
}

Simple Transcoding

If you are doing simple offline transcoding (no need for streaming, extra options, progress updates, etc) then you can use the process API:

var transcoding = require('transcoding');
transcoding.process(source, target, transcoding.profiles.APPLE_TV_2, {}, function(err, sourceInfo, targetInfo) {
  // Completed
});

Note that this effectively just wraps the advanced API, without the need to track events.

Advanced Transcoding

var transcoding = require('transcoding');
var task = transcoding.createTask(source, target, transcoding.profiles.APPLE_TV_2);

task.on('begin', function(sourceInfo, targetInfo) {
  // Transcoding beginning, info available
  console.log('transcoding beginning...');
  console.log('source:');
  console.log(util.inspect(sourceInfo));
  console.log('target:');
  console.log(util.inspect(targetInfo));
});
task.on('progress', function(progress) {
  // New progress made, currrently at timestamp out of duration
  // progress = {
  //   timestamp: 0,        // current seconds timestamp in the media
  //   duration: 0,         // total seconds in the media
  //   timeElapsed: 0,      // seconds elapsed so far
  //   timeEstimated: 0,    // seconds estimated for total task
  //   timeRemaining: 0,    // seconds remaining until done
  //   timeMultiplier: 2    // multiples of real time the transcoding is
  //                        // occuring in (2 = 2x media time)
  // }
  console.log(util.inspect(progress));
  console.log('progress ' + (progress.timestamp / progress.duration) + '%');
});
task.on('error', function(err) {
  // Error occurred, transcoding ending
  console.log('error: ' + err);
});
task.on('end', function() {
  // Transcoding has completed
  console.log('finished');
});

// Start transcoding
task.start();

// At any time, abort transcoding
task.stop();

HTTP Live Streaming

If you are targetting devices that support HTTP Live Streaming (like iOS), you can have the transcoder build the output in realtime as it processes. This enables playback while the transcoding is occuring, as well as some other fancy things such as client-side stream switching (changing audio channels/etc).

// TODO: API for this... something like:
// (where target is used as a base filename for all the extra stuff)
var task = transcoding.createTask(source, target, profile, {
  streaming: {
    segmentDuration: 10,
    allowCaching: true
  }
});
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