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flac.js Build Status

JavaScript FLAC (audio format) de- and encoder

Project WebsiteMinimal demo

flac.js encodes or decodes whole files to FLAC, the Free Lossless Audio Codec. Supported input formats are wav, rf64, w64, aif, flac (flac in its native container as well as in oga/ogg). It is supposed to do the same as the flac executable that can be built from the FLAC sources.

flac.js was built with Emscripten.

Building

If you just want to use flac.js, you don't have to build it. In this case, see using instead.

Prerequisites

  • A recent linux build system
  • Emscripten 1.25.0 installed and activated

Build script

Encoder

git clone git://github.com/Rillke/flac.js.git flacenc.js
cd flacenc.js
git checkout encoder
git submodule update --init
./make.sh

Using

A pre-compiled script together with some auxiliary scripts making use from JavaScript easier is in the /worker directory. iframe.html is a minimal usage example. Test it live. It starts the encoding process posting command: 'encode' to the worker:

var worker = new Worker( 'worker/EmsWorkerProxy.js' );
// Files to be read and posted back
// after encoding completed
var outData = {
	// File name
	'encoded.flac': {
		// MIME type
		'MIME': 'audio/flac'
	}
};

worker.onmessage = function( e ) {
	// Handle incoming data
};

// Prepare files etc.

// Post all data and the encode command
// to the web worker
worker.postMessage( {
	command: 'encode',
	args: args,
	outData: outData,
	fileData: storedFiles
} );
  • command: 'encode'|'prefetch' DOMString that either starts encoding (or decoding) or prefetching the worker script. Posting a prefetch command in advance is optional, depends on the user experience you'd like to create and does not require further arguments. If the script is not prefetched, it will be downloaded when 'encode' is invoked.
  • args: Array holding the command line arguments (DOMString)
  • outData: Object literal of information about the files that should be read out of the worker's file system after encoding completed
  • fileData: Object literal of input file data mapping file names to Uint8Arrays

A more extensive example is available on the project's website.

Bummer! A 3.5 MiB web worker!

Yeah, the data file - flac.data.js - is huge but conists mostly of null characters and compresses very well; a compressed size of 30.2 KB when sent gziped is possible.

In case one is just out for encoding to flac, one might replace worker/flac.js with worker/flac.encoder.js and worker/flac.data.js with flac.encoder.data.js in the downloaded project page. This way the worker is about 1 MiB in total (uncompressed).

The 3.5 MiB results from flac's decoder and analyzer's huge stack size.

Contributing

Submit patches to this GitHub repository or file issues.

License

See LICENSE.md