I am using WebAudio to play a sequence of notes. I have a playNote function which works well; I send it note frequency and start and stop times for each note. The generation of the sequence parameters occurs before the actual sound starts, which is a little confusing. The function just creates an oscillator for every note. (I tried other methods and this is the cleanest).
But I would like to stop the sequence asynchronously (e.g. when an external event occurs). I tried setting up a master Gain node that could be used to gate the output, but it seems it needs to be “inside” the function, so it can’t be controlled later on. If I try and turn off my gain object inside the function then it is too late – because the start & stop times have already been passed to the function.
Here is my function:
function playNote(audioContext,frequency, startTime, endTime, last) { gainNode = audioContext.createGain(); //to get smooth rise/fall oscillator = audioContext.createOscillator(); oscillator.frequency.value=frequency; oscillator.connect(gainNode); gainNode.connect(analyserScale); //analyser is global analyserScale.connect(audioContext.destination); gainNode.gain.exponentialRampToValueAtTime(toneOn, startTime + trf); gainNode.gain.exponentialRampToValueAtTime(toneOff, endTime+trf); oscillator.start(startTime); oscillator.stop(endTime); }
Any help appreciated!
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Answer
This does it: Web Audio API: Stop all scheduled sounds from playing. The solution is to keep track of the scheduled oscillators with an array.
The function now becomes: var oscs = []; //list of oscillators
function playNote(audioContext,frequency, startTime, endTime, last, index) { gainNode = audioContext.createGain(); //to get smooth rise/fall oscillator = audioContext.createOscillator(); oscillator.frequency.value=frequency; oscillator.connect(gainNode); //keep track of alll the oscs so that they can be switched off if scale is stopped by user oscs[index] = oscillator; gainNode.connect(analyserScale); //analyser is global analyserScale.connect(audioContext.destination); gainNode.gain.exponentialRampToValueAtTime(toneOn, startTime + trf); gainNode.gain.exponentialRampToValueAtTime(toneOff, endTime+trf); oscillator.start(startTime); oscillator.stop(endTime); }
Then code to stop the oscillators:
for(let i=0; i<oscs.length; i++) { if(oscs[i]){ oscs[i].stop(0); } }