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use local implementation of ima adpcm instead of sdr.js

This commit is contained in:
Jakob Ketterl 2020-01-05 23:26:27 +01:00
parent 15d351258f
commit c8c5ce8105
1 changed files with 48 additions and 1 deletions
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49
htdocs/lib/AudioEngine.js
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@ -14,7 +14,7 @@ function AudioEngine(maxBufferLength, audioReporter) {
this.allowed = this.audioContext.state === 'running';
this.started = false;
this.audioCodec = new sdrjs.ImaAdpcm();
this.audioCodec = new ImaAdpcmCodec();
this.compression = 'none';
this.setupResampling();
@ -228,3 +228,50 @@ AudioEngine.prototype.getBuffersize = function() {
if (!this.audioBuffers) return 0;
return this.audioBuffers.map(function(b){ return b.length; }).reduce(function(a, b){ return a + b; }, 0);
};
function ImaAdpcmCodec() {
this.stepIndex = 0;
this.predictor = 0;
this.step = 0;
}
ImaAdpcmCodec.imaIndexTable = [ -1, -1, -1, -1, 2, 4, 6, 8, -1, -1, -1, -1, 2, 4, 6, 8 ];
ImaAdpcmCodec.imaStepTable = [
7, 8, 9, 10, 11, 12, 13, 14, 16, 17,
19, 21, 23, 25, 28, 31, 34, 37, 41, 45,
50, 55, 60, 66, 73, 80, 88, 97, 107, 118,
130, 143, 157, 173, 190, 209, 230, 253, 279, 307,
337, 371, 408, 449, 494, 544, 598, 658, 724, 796,
876, 963, 1060, 1166, 1282, 1411, 1552, 1707, 1878, 2066,
2272, 2499, 2749, 3024, 3327, 3660, 4026, 4428, 4871, 5358,
5894, 6484, 7132, 7845, 8630, 9493, 10442, 11487, 12635, 13899,
15289, 16818, 18500, 20350, 22385, 24623, 27086, 29794, 32767
];
ImaAdpcmCodec.prototype.decode = function(data) {
var output = new Int16Array(data.length * 2);
for (var i = 0; i < data.length; i++) {
output[i * 2] = this.decodeNibble(data[i] & 0x0F);
output[i * 2 + 1] = this.decodeNibble((data[i] >> 4) & 0x0F);
}
return output;
};
ImaAdpcmCodec.prototype.decodeNibble = function(nibble) {
this.stepIndex += ImaAdpcmCodec.imaIndexTable[nibble];
this.stepIndex = Math.min(Math.max(this.stepIndex, 0), 88);
var diff = this.step >> 3;
if (nibble & 1) diff += this.step >> 2;
if (nibble & 2) diff += this.step >> 1;
if (nibble & 4) diff += this.step;
if (nibble & 8) diff = -diff;
this.predictor += diff;
this.predictor = Math.min(Math.max(this.predictor, -32768), 32767);
this.step = ImaAdpcmCodec.imaStepTable[this.stepIndex];
return this.predictor;
};