How can I get the current time of the AudioBufferSourceNode?
When working with audio elements ( <audio>
) or contexts ( AudioContext
), you can check their property currentTime
to know exactly the playback time of your buffer.
This is all great until I created multiple sources (or AudioBufferSourceNode
) in one AudioContext
.
Sources may be reproduced at different times, so I will need to find out their respective ones currentTime
to illustrate:
Some basic codes to work:
buffer1 = [0,1,0]; //not real buffers
buffer2 = [1,0,1];
ctx = new AudioContext();
source1 = ctx.createBufferSourceNode();
source1.buffer = buffer1;
source1.connect(ctx.destination);
source1.start(0);
source2 = ctx.createBufferSourceNode();
source2.buffer = buffer2;
source2.connect(ctx.destination);
setTimeout(1000/*some time later*/){
source2.start(0);
}
setTimeout(1500/*some more time later*/){
getCurrentTime();
}
function getCurrentTime(){
/* magic */
/* more magic */
console.log("the sources currentTime values are obviously 1500 (source1) and 500 (source2).");
}
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I usually wrap a sound source node that monitors the playback state. I've tried to keep the code below to a minimum to show the basics.
The basic idea is to keep track of the sound's start time and the time the sound is "paused", and use these values to get the current time and resume playback from the paused position.
I put a working example in the codepen
function createSound(buffer, context) {
var sourceNode = null,
startedAt = 0,
pausedAt = 0,
playing = false;
var play = function() {
var offset = pausedAt;
sourceNode = context.createBufferSource();
sourceNode.connect(context.destination);
sourceNode.buffer = buffer;
sourceNode.start(0, offset);
startedAt = context.currentTime - offset;
pausedAt = 0;
playing = true;
};
var pause = function() {
var elapsed = context.currentTime - startedAt;
stop();
pausedAt = elapsed;
};
var stop = function() {
if (sourceNode) {
sourceNode.disconnect();
sourceNode.stop(0);
sourceNode = null;
}
pausedAt = 0;
startedAt = 0;
playing = false;
};
var getPlaying = function() {
return playing;
};
var getCurrentTime = function() {
if(pausedAt) {
return pausedAt;
}
if(startedAt) {
return context.currentTime - startedAt;
}
return 0;
};
var getDuration = function() {
return buffer.duration;
};
return {
getCurrentTime: getCurrentTime,
getDuration: getDuration,
getPlaying: getPlaying,
play: play,
pause: pause,
stop: stop
};
}
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