util.js

/**
 * Copyright 2014 IBM Corp. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

"use strict";

var path = require("path"),
	fs = require("fs"),
	mkdirp = require("mkdirp"),
	uuid = require("node-uuid"),
	sox = require("sox");

var dest = path.resolve("./transcode");
mkdirp(dest, function(err) {
	if (err) {
		throw err;
	}
});

var transcode = function(input, output, cb) {
	var job = sox.transcode(input, output, {
		format: "wav",
	});
	job.on("error", function (err) {
		console.error(err)
	});
	job.on("progress", function (amountDone, amountTotal) {
		console.log("progress", amountDone, amountTotal)
	});
	job.on("end", function () {
		console.log("Transcoding finished.")
		cb()
	});
	job.start()
}

module.exports = {
	/**
	 * Work around an iOS bug which prevents WAV files from playing if a valid
	 * duration is not specified. This occurs when streaming an audio file
	 * directly from the source.
	 **/
	fixEncoding: function(stream, res) {
		var id = uuid.v4();
		var input = path.join(dest, "in_" + id + ".wav");
		var writeStream = fs.createWriteStream(input);
		stream.pipe(writeStream);
		writeStream.on("finish", function() {
			var output = path.join(dest, "out_" + id + ".wav");
			transcode(input, output, function() {
				res.sendFile(output, null, function(err) {
					fs.unlink(input);
					fs.unlink(output);
				});
			});
		});
	}
};