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Readme.md

Node libavcodec bindings BuildStatus

navcodec is a module that aims to provide a node wrapper for the excellent libavcodec library. The module does not aim to make a 1 to 1 mapping between this library and javascript. Instead the aim is to create a new javascript API inspired by the underlying library that is more javascript oriented and easier to use.

The initial priority will be to make the transcoding use case, and later move to other uses cases such as playing, filtering, editing, etc.

Follow optimalbits for news and updates regarding this library.

Transcoding

navcodec = require('navcodec');

navcodec.open('myinput.mov', function(err, media){
  if(media){
    media.addOutput('myoutput.mp4', {
        width:640,
        height:480,
        audioBitrate:128000,
        videoBitrate:500000
    });

    media.transcode(function(err, progress, time){
      console.log(progress);
      if(progress === 100){
        console.log('total transcoding time:'+time);
      }
    }
  }
});

This will transcode myinput.mov into myoutput.mp4 according to the given options. The callback will be called with a progress variable between 0 and 100.

Since the transcode uses mostly libavcodec optimized functions, the above example will run really fast.

Available options (and their defaults):

width ( input width )
height (input height )
videoBitrate (input bitrate if available, 0 otherwise)
videoCodec ( standard codec for current file container)
keepAspectRatio (true)
audioBitrate (input bitrate if available, 0 otherwise)
sampleRate (44100)
channels (2),
audioCodec (standard codec for current file container)
skipAudio (false)
skipVideo (false)
maxVideoFrames (inf)
videoFrameInterval (1)

Multiple outputs

Several outputs can be added to the media object, and when transcoding the data will be processed in parallel. This is quite convenient when generating thumbnails (which will be very cheap to generate), or if several output formats are required (will only require one decoding process of the input file):

navcodec.open('myinput.mov', function(err, media){
  if(media){
    media.addOutput('myoutput.mp4', {
        width:640,
        height:480,
        audioBitrate:128000,
        videoBitrate:500000
    });

    media.addOutput('thumbnail.mp4', {
        width:80,
        height:60,
        skipAudio:true,
        videoBitrate:50000
    });

    media.transcode(function(err, progress, time){
      console.log(progress);
      if(progress === 100){
        console.log('total transcoding time:'+time);
      }
    });
  }
});

Jpeg Thumbnails

A very common use case is the generation of a jpeg thumbnail to represent some video sequence. This can be easily accomplished by calling the function thumbnail. It can be called once or several times if different options are required. See the following example, where for every generated thumbnail a time offset is choosen:

navcodec.open('myinput.mov', function(err, media){
  if(media){
    media.thumbnail([{'first128.jpg':1, 'secong128.jpg:100.5'},{width:128,height:128});
    media.thumbnail([{'first64.jpg':1, 'secong64.jpg:100.5'},{width:64,height:64});

    media.transcode(function(err, progress, time){
      console.log(progress);
      if(progress === 100){
        console.log('total transcoding time:'+time);
      }
    });
  }
});

Note that generating thumbnails at the same time as transcoding a full video is a extreamly cheap operation.

Metadata

Metadata is available after opening the media file. Its just a javascript object with keys and values:

navcodec.open('walk.flac', function(err, media){
  if(media){
    console.log(media.metadata);
  }
});

The previous example would result in the following output:

{
  ARTIST: 'Foo Fighters',
  TITLE: 'Walk',
  ALBUM: 'Wasting Light',
  DATE: '2011',
  track: '11',
  TOTALTRACKS: '11',
  GENRE: 'Rock',
  album_artist: 'Foo Fighters',
  'ALBUM ARTIST': 'Foo Fighters',
  COMMENT: 'EAC V1.0 beta 1, Secure Mode, Test & Copy, AccurateRip, FLAC 1.2.1b -8' 
}

Besides the 'metadata' property, other convenient properties are also available in the media object:

width
height
videoBitrate
audioBitrate
bitrate
samplerate
duration

Optimize for Web

h.264 files created by libavcodec include the moov atom block at the end of the file (Understanding the MPEG-4 movie atom).

navcodec provides a function called relocateMoov that will move the moov atom at the begining of the file, thus making it better for seeking in a web based player. Example:

navcodec.relocateMoov('myinput.mp4','myoutput.mp4', function(err){
  if(err){
    console.log(err);
  }
});

Install

navcodec depends on libavcodec, and this library must be installed before you can install this module using npm.

The library needed is libavcodec version 0.8 and above. Version 0.8 includes some new APIs, that are used by this extension.

For most unixes there are packages available, in ubuntu for example use libavcodec-dev. If you want you can also compile the source code with your preferred settings, this can be useful if you want to get the maximum performance from the library.

For Mac OSX use brew and install the ffmpeg package.

brew install ffmpeg

Note that version 0.8 of libavcodec is brand new and the afore mentioned package managers may not have yet updated it.

When the libavcodec dependencies are fulfilled, just use npm to install the package:

npm install navcodec

Compiling libavcodec (Recommended)

  • Download the latest stable 0.8 release from libav.org

  • Uncompress the tarball, Ex:

    tar -xvf libav-0.8.tar.gz cd libav-0.8

  • Configure your makefile, example:

    ./configure  --prefix=/usr/local --enable-shared --enable-gpl --enable-version3 --enable-nonfree --enable-hardcoded-tables --cc=/usr/bin/clang --enable-libfaac --enable-libmp3lame --enable-libtheora --enable-libvorbis --enable-libvpx --enable-libxvid --enable-libx264
    

You may want to add some hardware acceleration flags for your architecture, for example:

--enable-vda  (Mac OS)
--enable-vaapi (Linux/Unix Intel)
--enable-vdpau (Linux/Unix Nvidia)

you can get a list of other configuration options using:

./configure --help
  • Compile the libraries:

    make
    
  • Install

    make install
    

References

Ubuntu HOWTO: Install and use the latest FFmpeg and x264

Todo

  • Make Asynchronous.
  • AC35.1 to stereo transcoding.
  • multiple pass encoding.
  • Add support for libavfilter.

License

Copyright(c) 2012 Optimal Bits Sweden AB. All rights reserved.

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

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