Tone.js/test/helper/CompareToFile.js

define(["helper/Offline", "Tone/core/Buffer", "deps/audiobuffer-to-wav", "deps/fft"], function(Offline, Buffer, audioBufferToWav, FFT){

	if (window.__karma__){
		Buffer.baseUrl = "/base/test/";
	}

	return function(callback, url, threshold, RENDER_NEW){
		if (!RENDER_NEW){

			threshold = threshold || 20;
			var baseUrl = "./audio/compare/";
			return Buffer.fromUrl(baseUrl+url).then(function(buffer){
				return Offline(callback, buffer.duration, buffer.numberOfChannels).then(function(renderedBuffer){
					return {
						rendered : renderedBuffer,
						target : buffer
					};
				});
			}).then(function(buffers){
				//go through and compare everything
				var renderedValues = buffers.rendered.toArray();
				var targetValues = buffers.target.toArray();
				targetValues.forEach(function(channel, channelNumber){
					var fftSize = 2048;
					var renderedChannel = renderedValues[channelNumber];
					for (var i = 0; i < channel.length; i+=fftSize){
						if (i + fftSize <= channel.length){
							var renderedPhasors = FFT.fft(renderedChannel.slice(i, i+fftSize));
							var targetPhasors = FFT.fft(channel.slice(i, i+fftSize));
							var renderedMagnitudes = FFT.util.fftMag(renderedPhasors);
							var targetMagnitudes = FFT.util.fftMag(targetPhasors);
							targetMagnitudes.forEach(function(value, index){
								expect(value).to.be.closeTo(renderedMagnitudes[index], threshold);
							});
						}
					}
				});
			});

		} else {
			var duration = threshold || 1;
			return Offline(callback, duration, 2).then(function(buffer){
				var wave = audioBufferToWav(buffer.get());
				var blob = new Blob([wave], { type : "audio/wav" });
				var blobUrl = window.URL.createObjectURL(blob);
				var a = document.createElement("a");
				a.href = blobUrl;
				a.download = url;
				a.click();
				window.URL.revokeObjectURL(blobUrl);
			});
		}
	};

});