Hooklock

Hook + Clock = Hooklock, hook your clocks together

Introduction

This module provides you a stream.Transform that lock your local clock with source clock.

Say you have wanna sync a sequence of timing-sensitive events (like MIDI data or game control events) with your local timeline (like Web Audio API currentTime or nodejs hrtime). The offset between two events eventA.time and eventB.time is offset, after transfer them to your local timeline eventA.happendAt and eventB.happendAt, the newOffset = eventA.happenedAt - eventB.happenedAt should remains the same ( offset === newOffset). hooklock will do the job for you.

If for some reason at some point a new transfered time is already behind the current time, hooklock will re-align the two timelines to make sure all following events are still retain the same intervals (Due to this strategy, the following events will be out-of-sync with previous events, so don't use this module if this is not your desired behavior).

Usage

Init hooklock with options

var Hooklock = require('hooklock'),
    options = {
        threshold: 100,
        latency: 200,
        clock: function () {
            var time = process.hrtime();
            return time[0] * 1e3 + time[1] / 1e6;
        }
    };

var hook = new Hooklock(options);

All options are optional (This sentence sounds good, isn't it?). Default values are:

• threshold: 100
• latency: 100
• clock: use right-now

After instantiation, you can start to pipe or write events to it.

    hook.write({
        data: Math.random(),
        timestamp: 50
    });

    hook.write({
        data: Math.random(),
        timestamp: 100
    });

    hook.write({
        data: Math.random(),
        timestamp: 150 
    });