navcodec provides a high level and flexible javascript module for video and audio transcoding based on the excelent libavcodec(from the FFmpeg team) library.
This module can transcode almost any known video and audio format efficiently, it can generate multiple thumbnails or output video in multiple resolutions in parallel quickly with low memory consumption while also optimizing the output for web reproduction.
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#Examples
navcodec = require('navcodec');
navcodec.open('myinput.mov', null, function(err, media){
if(media){
media.addOutput('myoutput.mp4', {
width:640,
height:480,
audioBitrate:128000,
videoBitrate:500000
});
media.transcode(function(err, progress, finished, time){
console.log(progress);
if(finished){
console.log("Total transcoding time: " + time + "ms");
}
}
}
});
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):
// Input
itsoffset (n/a)
y (true)
stats (true)
logLevel (n/a)
// Output
streamCopy (n/a, nullfies a videoBitrate, videoCodec, audioBitrate, audioCodec, sampleRate)
// Video
width (input width)
height (input height)
videoBitrate (input bitrate if available, 0 otherwise)
videoCodec (standard codec for current file container)
keepAspectRatio (true)
rotate ('clock' for clockwise, 'cclock' for counter clockwise)
fps (specify the output frames per second)
minFps (specify the output minimum frames per second)
skipVideo (false)
skipVideoFrames (0)*
videoBSF (n/a)
format (n/a)
// Audio
audioBitrate (input bitrate if available, 0 otherwise)
sampleRate (44100)
channels (2)
audioCodec (standard codec for current file container)
skipAudio (false)
format (n/a)
// Thumbnails
keepAspectRatio (true)
width (input width)
height (input height)
*Experimental feature.
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', null, 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 + "ms");
}
});
}
});
##Resolution video pyramid
You can use Navcodec to transcode a video into multiple resolutions, forming a pyramid of resolutions, than can later be used to deliver the most efficient version for a given client in terms of screen resolution or bandwidth.
Media##addPyramid(basename: string, maxSize, minSize, options);
So for example, if you want to transcode to a pyramid of images similar to the ones in you tube:
media.addPyramid('new.mp4', {width: 1920}, {witdh: 240}, {keepAspectRatio: true, videoBitrate: '2000k'});
This will produce a pyramid of videos like the following:
1080-new.mp4
70
##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', null, 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 + "ms");
}
});
}
});
Note that generating thumbnails at the same time as transcoding a full video is a extreamly cheap operation.
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
Normally, a mp4 file created by ffmpeg or any other transcoder, places the index at the end of the file (moov block). This makes impossible for a web browser to perform seeking until the whole file has been downloaded.
Navcodec includes a useful utility 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);
}
});
navcodec depends on libavcodec, and this library must be installed before you can install this module using npm.
The current version of libavcodec needed by navcodec is 0.9.1 and above.
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 0.9.x 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
-
Download the latest stable 0.9.x release from libav.org
-
Uncompress the tarball, Ex:
tar -xvf libav-0.9.1.tar.gz && cd libav-0.9.1 -
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 -
Notes
Mac users will need to install Xcode in order to be able to compile libavcodec by themselves.
It may be needed to install libvpx separatelly if you need WebM support (in Mac):
brew install libvpx
Ubuntu HOWTO: Install and use the latest FFmpeg and x264
- Multiple pass encoding
- Support presets
- Support for filters
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