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/* |
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JJY.js: JJY time signal emulation/transmission library |
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Copyright (c) @plugnburn (831337.xyz) 2017 |
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@license ISC |
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*/ |
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function JJY(distorter) { //JJY constructor |
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distorter = parseFloat(distorter) |
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//create pre-filled constant array for efficient copying |
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var codeProto = '200000000200000000020000000002000000000200000000020000000002'.split('').map(Number) |
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function toBCD(val) { |
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return val%10 + (((val/10)%10)<<4) + ((val/100)<<8) |
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} |
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function calcParity(val){ |
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var i = 0; |
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while(val) { |
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i ^= val & 1 |
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val >>>= 1 |
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} |
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return i |
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} |
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function jjyTimecode(timeObj) { //generate a JJY timecode from any given Date object |
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var ts = { |
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min: toBCD(timeObj.getUTCMinutes()), |
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hour: toBCD(timeObj.getUTCHours()), |
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day: toBCD(Math.floor((timeObj - new Date(timeObj.getUTCFullYear(),0,0,0,0))/864e5)), |
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year: toBCD(timeObj.getUTCFullYear() % 100), |
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weekDay: timeObj.getUTCDay() |
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}, timeCode = codeProto.slice(); |
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//populate minute |
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timeCode[1] = (ts.min>>6)&1 |
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timeCode[2] = (ts.min>>5)&1 |
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timeCode[3] = (ts.min>>4)&1 |
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timeCode[5] = (ts.min>>3)&1 |
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timeCode[6] = (ts.min>>2)&1 |
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timeCode[7] = (ts.min>>1)&1 |
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timeCode[8] = ts.min&1 |
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//populate hour |
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timeCode[12] = (ts.hour>>5)&1 |
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timeCode[13] = (ts.hour>>4)&1 |
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timeCode[15] = (ts.hour>>3)&1 |
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timeCode[16] = (ts.hour>>2)&1 |
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timeCode[17] = (ts.hour>>1)&1 |
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timeCode[18] = ts.hour&1 |
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//populate day number |
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timeCode[22] = (ts.day>>9)&1 |
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timeCode[23] = (ts.day>>8)&1 |
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timeCode[25] = (ts.day>>7)&1 |
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timeCode[26] = (ts.day>>6)&1 |
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timeCode[27] = (ts.day>>5)&1 |
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timeCode[28] = (ts.day>>4)&1 |
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timeCode[30] = (ts.day>>3)&1 |
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timeCode[31] = (ts.day>>2)&1 |
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timeCode[32] = (ts.day>>1)&1 |
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timeCode[33] = ts.day&1 |
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//populate parity bits |
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timeCode[36] = calcParity(ts.hour) |
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timeCode[37] = calcParity(ts.min) |
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//populate year |
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timeCode[41] = (ts.year>>7)&1 |
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timeCode[42] = (ts.year>>6)&1 |
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timeCode[43] = (ts.year>>5)&1 |
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timeCode[44] = (ts.year>>4)&1 |
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timeCode[45] = (ts.year>>3)&1 |
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timeCode[46] = (ts.year>>2)&1 |
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timeCode[47] = (ts.year>>1)&1 |
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timeCode[48] = ts.year&1 |
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//populate day of the week |
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timeCode[50] = ts.weekDay>>2 |
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timeCode[51] = (ts.weekDay>>1)&1 |
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timeCode[52] = ts.weekDay&1 |
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return timeCode |
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} |
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function getJJYTimeCode(timeObj) { |
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var timeRep = timeObj || new Date(Date.now() + 324e5); |
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return { |
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bitCode: jjyTimecode(timeRep), |
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cs: timeRep.getUTCSeconds() |
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} |
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} |
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return { |
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getTimeCode: getJJYTimeCode, //exposed for getting timecode information in non-browser environments |
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run: function(tObj) { //browser-only function, requires Web Audio API support |
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var ctx = new (window.AudioContext || window.webkitAudioContext)(), |
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sr = ctx.sampleRate, |
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opFreq = 40000/3, |
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rp = opFreq/sr, bufSet = [], pwm = [.8, .5, .2]; |
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if(isNaN(distorter) || distorter < 2) |
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distorter = sr/3 |
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ctx.createBuffer = ctx.createBuffer || ctx.webkitCreateBuffer; |
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ctx.createBufferSource = ctx.createBufferSource || ctx.webkitCreateBufferSource; |
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performance.now = performance.now || performance.webkitNow || function(){return (new Date).getTime()} |
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secondTick = (function(tm){ |
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var px = 0, py = 0, dx = 0; |
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return function(cb){ |
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px = performance.now() |
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setTimeout(function(){ |
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dx = (py = performance.now()) - px - tm |
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px = py |
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cb() |
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}, tm - dx/2) |
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} |
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})(1000) |
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// pre-populate the buffers |
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for(var i=0;i<3;i++) { |
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var sLen = sr*pwm[i]; |
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bufSet[i] = ctx.createBuffer(1, sLen, sr); |
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var cData = bufSet[i].getChannelData(0); |
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for(var k=0;k<sLen;k++) |
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cData[k] = Math.floor(distorter*Math.sin(2 * Math.PI * k * rp))/distorter |
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} |
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// play back the timecode |
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var renderMinute = function() { |
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var sigInfo = getJJYTimeCode(tObj), currentIndex = sigInfo.cs, |
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renderSecond = function() { |
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secondTick(currentIndex<59 ? renderSecond : renderMinute) |
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var bs = ctx.createBufferSource() |
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bs.buffer = bufSet[sigInfo.bitCode[currentIndex]] |
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bs.connect(ctx.destination) |
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bs.start() |
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currentIndex++ |
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} |
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renderSecond() |
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} |
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renderMinute() |
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} |
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} |
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} |
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if(typeof module !== 'undefined' && module.exports && this.module !== module) |
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module.exports = JJY() |
I don't know if you can do a pull request to a gist but I have changed the code so that it adapts to the local time zone instead of being hardcoded to Japan (UTC+9). I have modified a single function "getJJYTimeCode" as follows: