(Web Audio API) A test to see if accumulating sample time drifts away from AudioContext.currentTime.

drift.html

<script>
    var ac = new webkitAudioContext;
    var j = ac.createScriptProcessor(1024, 1, 1);
    
    var startTime, startTimeGrabbed = false, samples = 0, sampleCountTime = 0, frames = 0;
    
    j.onaudioprocess = function (event) {
        if (!startTimeGrabbed) {
            startTime = ac.currentTime;
            samples = 0;
            sampleCountTime = ac.currentTime;
            frames = 0;
            startTimeGrabbed = true;
        }

        var drift_ms = Math.round(1000 * (sampleCountTime - ac.currentTime));

        if ((frames++) % 100 === 0) {
            console.log("Frame stats = " + JSON.stringify({
                startTime: startTime, 
                samples: samples, 
                sampleCountTime: sampleCountTime, 
                currentTime: ac.currentTime,
                drift_ms: drift_ms
            }));
        }

        if (Math.abs(sampleCountTime - ac.currentTime) > 0.1) {
            console.log("Drift = " + drift_ms + " ms");
        }

        samples += event.inputBuffer.length;
        sampleCountTime += event.inputBuffer.duration;
    };
    
    j.connect(ac.destination);
</script>