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replace with a more robust state engine implementation

This commit is contained in:
Jakob Ketterl 2023-01-28 16:37:32 +01:00
parent d79a1396a6
commit b1ac8caf9b
1 changed files with 34 additions and 25 deletions
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59
htdocs/lib/AudioEngine.js
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@ -331,7 +331,9 @@ ImaAdpcmCodec.prototype.reset = function() {
this.synchronized = 0;
this.syncWord = "SYNC";
this.syncCounter = 0;
this.skip = 0;
this.phase = 0;
this.syncBuffer = new Uint8Array(4);
this.syncBufferIndex = 0;
};
ImaAdpcmCodec.imaIndexTable = [ -1, -1, -1, -1, 2, 4, 6, 8, -1, -1, -1, -1, 2, 4, 6, 8 ];
@ -359,38 +361,45 @@ ImaAdpcmCodec.prototype.decode = function(data) {
ImaAdpcmCodec.prototype.decodeWithSync = function(data) {
var output = new Int16Array(data.length * 2);
var index = this.skip;
var oi = 0;
while (index < data.length) {
while (this.synchronized < 4 && index < data.length) {
if (data[index] === this.syncWord.charCodeAt(this.synchronized)) {
this.synchronized++;
} else {
this.synchronized = 0;
}
index++;
if (this.synchronized === 4) {
if (index + 4 < data.length) {
var syncData = new Int16Array(data.buffer.slice(index, index + 4));
for (var index = 0; index < data.length; index++) {
switch (this.phase) {
case 0:
// search for sync word
if (data[index] !== this.syncWord.charCodeAt(this.synchronized++)) {
// reset if data is unexpected
this.synchronized = 0;
}
// if sync word has been found pass on to next phase
if (this.synchronized === 4) {
this.syncBufferIndex = 0;
this.phase = 1;
}
break;
case 1:
// read codec runtime data from stream
this.syncBuffer[this.syncBufferIndex++] = data[index];
// if data is complete, apply and pass on to next phase
if (this.syncBufferIndex === 4) {
var syncData = new Int16Array(this.syncBuffer.buffer);
this.stepIndex = syncData[0];
this.predictor = syncData[1];
this.syncCounter = 1000;
this.phase = 2;
}
this.syncCounter = 1000;
index += 4;
break;
}
}
while (index < data.length) {
if (this.syncCounter-- < 0) {
this.synchronized = 0;
case 2:
// decode actual audio data
output[oi++] = this.decodeNibble(data[index] & 0x0F);
output[oi++] = this.decodeNibble(data[index] >> 4);
// if the next sync keyword is due, reset and return to phase 0
if (this.syncCounter-- === 0) {
this.synchronized = 0;
this.phase = 0;
}
break;
}
output[oi++] = this.decodeNibble(data[index] & 0x0F);
output[oi++] = this.decodeNibble(data[index] >> 4);
index++;
}
}
this.skip = index - data.length;
return output.slice(0, oi);
};