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POCreate a beeping sound using Mozilla audio API
 

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  1. POCreate a beeping sound using Mozilla audio API
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    <p>I'm investigating using the mozilla audio API tone generator:</p> <pre><code> 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, tailPosition; // 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.subarray(tailPosition)); currentWritePosition += written; tailPosition += written; if(tailPosition &lt; tail.length) { // Not all the data was written, saving the tail... 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 &gt; 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 &lt; soundData.length) { // Not all the data was written, saving the tail. tail = soundData; tailPosition = 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&lt;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; } </code></pre> <p>I'd like this tone to be on for 500ms then off for 500ms then repeat until a stop button is pressed. I thought I could just do this by setting the sample numbers 22,050 to 44,100 to zero. However this method does not seem to work. I think it's because the function to repopulate the buffer occurs every 100ms, but this is now beyond the limit of my knowledge. Any help would be very much appreciated.</p>
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