Web Audio API - Getting the current offset in a song & onstarted event for a source

I'm playing a segment of a music track using a source in the Web Audio API.

var source = audioCtx.createBufferSource();

source.buffer = audioBuffer;
source.connect(audioCtx.destination);

source.start(when, offset, duration);

I know that there is an event listener that I can use when the source has finished playing, source.onended. Is there an event listener that I can use when the source starts? e.g. source.onstarted?

Furthermore, can at any point get what part of the track is currently playing from a source? Or perhaps even from the audioCtx?

e.g. source.getCurrentOffset(); // 0:21

I would like to avoid my current strategy of starting a setTimeout when the source starts as it's not accurate.

Example

source.start(when, offset, duration);

setTimeout(function() {
    console.log("The track has started!");
}, 1000 * when);

Thanks!