= document.getElementById('audio'); // After loadedmetadata event, following media element attributes are known: channels = audio.mozChannels; rate = audio.mozSampleRate; frameBufferLength = audio.mozFrameBufferLength; } function audioAvailable(event) { var samples = event.frameBuffer; var time = event.time; for (var i = 0; i < frameBufferLength; i++) { // Do something with the audio data as it is played. processSample(samples[i], channels, rate); } }
<input type="text" size="4" id="freq" value="440"><label for="hz">Hz</label> <button onclick="start()">play</button> <button onclick="stop()">stop</button> <script type="text/javascript"> function AudioDataDestination(sampleRate, readFn) { // Initialize the audio output. var audio = new Audio(); audio.mozSetup(1, sampleRate); var currentWritePosition = 0; var prebufferSize = sampleRate / 2; // buffer 500ms var tail = null; // The function called with regular interval to populate // the audio output buffer. setInterval(function() { var written; // Check if some data was not written in previous attempts. if(tail) { written = audio.mozWriteAudio(tail); currentWritePosition += written; if(written < tail.length) { // Not all the data was written, saving the tail... tail = tail.slice(written); return; // ... and exit the function. } tail = null; } // Check if we need add some data to the audio output. var currentPosition = audio.mozCurrentSampleOffset(); var available = currentPosition + prebufferSize - currentWritePosition; if(available > 0) { // Request some sound data from the callback function. var soundData = new Float32Array(available); readFn(soundData); // Writting the data. written = audio.mozWriteAudio(soundData); if(written < soundData.length) { // Not all the data was written, saving the tail. tail = soundData.slice(written); } currentWritePosition += written; } }, 100); } // Control and generate the sound. var frequency = 0, currentSoundSample; var sampleRate = 44100; function requestSoundData(soundData) { if (!frequency) { return; // no sound selected } var k = 2* Math.PI * frequency / sampleRate; for (var i=0, size=soundData.length; i<size; i++) { soundData[i] = Math.sin(k * currentSoundSample++); } } var audioDestination = new AudioDataDestination(sampleRate, requestSoundData); function start() { currentSoundSample = 0; frequency = parseFloat(document.getElementById("freq").value); } function stop() { frequency = 0; } </script>
channels) { for(var b=0;b<bufferSize;b++) { var period = ((absoluteBufferPos + b) % 100) / 100; period *= 2 * Math.PI; var val = Math.sin(period); bridge.addToBuffer(val,val); } absoluteBufferPos += bufferSize; };
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![[...] var audio = new Audio(); audio.mozSetup(1, sampleRate); [...] written](https://files.speakerdeck.com/presentations/6fbe46709faf0130ed0c0ebc2299228d/slide_32.jpg){kind=link}
