Skip to content

Commit

Permalink
High pass filteer addition for DC bias removal. thanks gbdev team.
Browse files Browse the repository at this point in the history
  • Loading branch information
@taisel
taisel committed Jan 6, 2012
1 parent 3b35b40 commit 93e1bd6
Showing 1 changed file with 25 additions and 15 deletions.
40 changes: 25 additions & 15 deletions js/GameBoyCore.js
View file
Expand Up @@ -129,6 +129,8 @@ function GameBoyCore(canvas, ROMImage) {
//Vin Shit:
this.VinLeftChannelMasterVolume = 1; //Computed post-mixing volume.
this.VinRightChannelMasterVolume = 1; //Computed post-mixing volume.
this.capacitorCharge = 0;
this.capacitorFactor = 0;
//Channel paths enabled:
this.leftChannel0 = false;
this.leftChannel1 = false;
Expand Down Expand Up @@ -4239,7 +4241,8 @@ GameBoyCore.prototype.saveState = function () {
this.interruptsRequested,
this.interruptsEnabled,
this.remainingClocks,
this.colorizedGBPalettes
this.colorizedGBPalettes,
this.capacitorCharge
];
}
GameBoyCore.prototype.returnFromState = function (returnedFrom) {
Expand Down Expand Up @@ -4417,7 +4420,8 @@ GameBoyCore.prototype.returnFromState = function (returnedFrom) {
this.interruptsEnabled = state[index++];
this.checkIRQMatching();
this.remainingClocks = state[index++];
this.colorizedGBPalettes = state[index];
this.colorizedGBPalettes = state[index++];
this.capacitorCharge = state[index];
this.fromSaveState = true;
this.TICKTable = this.toTypedArray(this.TICKTable, "uint8");
this.SecondaryTICKTable = this.toTypedArray(this.SecondaryTICKTable, "uint8");
Expand Down Expand Up @@ -5101,7 +5105,7 @@ GameBoyCore.prototype.initSound = function () {
this.sampleSize = settings[14] / 1000 * settings[6];
this.audioHandle = new XAudioServer(this.soundChannelsAllocated, settings[14], (this.sampleSize * 4) << this.soundFrameShifter, (this.sampleSize * 20) << this.soundFrameShifter, function (sampleCount) {
return parentObj.audioUnderRun(sampleCount);
}, -1);
}, 0);
cout("...Audio Channels: " + this.soundChannelsAllocated, 0);
cout("...Sample Rate: " + settings[14], 0);
this.initAudioBuffer();
Expand Down Expand Up @@ -5129,6 +5133,7 @@ GameBoyCore.prototype.initAudioBuffer = function () {
cout("...Samples per clock cycle (Per Channel): " + this.samplesOut, 0);
this.numSamplesTotal = this.sampleSize << this.soundFrameShifter;
this.currentBuffer = this.getTypedArray(this.numSamplesTotal, -1, "float32");
this.capacitorFactor = Math.pow(0.999958, (4194304 / 2) / settings[14]);
this.intializeWhiteNoise();
}
GameBoyCore.prototype.intializeWhiteNoise = function () {
Expand Down Expand Up @@ -5297,15 +5302,20 @@ GameBoyCore.prototype.initializeAudioStartState = function (resetType) {
this.VinLeftChannelMasterVolume = 1;
this.VinRightChannelMasterVolume = 1;
}
GameBoyCore.prototype.highPass = function (signalIn) {
var out = signalIn - this.capacitorCharge;
this.capacitorCharge = signalIn - out * this.capacitorFactor;
return out;
}
//Below are the audio generation functions timed against the CPU:
GameBoyCore.prototype.generateAudio = function (numSamples) {
if (this.soundMasterEnabled) {
if (!settings[1]) { //Split Mono & Stereo into two, to avoid this if statement every iteration of the loop.
while (--numSamples > -1) {
//STEREO
this.audioChannelsComputeStereo();
this.currentBuffer[this.audioIndex++] = this.currentSampleLeft * this.VinLeftChannelMasterVolume - 1;
this.currentBuffer[this.audioIndex++] = this.currentSampleRight * this.VinRightChannelMasterVolume - 1;
this.currentBuffer[this.audioIndex++] = this.highPass(this.currentSampleLeft * this.VinLeftChannelMasterVolume - 1);
this.currentBuffer[this.audioIndex++] = this.highPass(this.currentSampleRight * this.VinRightChannelMasterVolume - 1);
if (this.audioIndex == this.numSamplesTotal) {
this.audioIndex = 0;
this.audioHandle.writeAudio(this.currentBuffer);
Expand All @@ -5316,7 +5326,7 @@ GameBoyCore.prototype.generateAudio = function (numSamples) {
while (--numSamples > -1) {
//MONO
this.audioChannelsComputeMono();
this.currentBuffer[this.audioIndex++] = this.currentSampleRight * this.VinRightChannelMasterVolume - 1;
this.currentBuffer[this.audioIndex++] = this.highPass(this.currentSampleRight * this.VinRightChannelMasterVolume - 1);
if (this.audioIndex == this.numSamplesTotal) {
this.audioIndex = 0;
this.audioHandle.writeAudio(this.currentBuffer);
Expand All @@ -5329,8 +5339,8 @@ GameBoyCore.prototype.generateAudio = function (numSamples) {
if (!settings[1]) {
while (--numSamples > -1) {
//STEREO
this.currentBuffer[this.audioIndex++] = -1;
this.currentBuffer[this.audioIndex++] = -1;
this.currentBuffer[this.audioIndex++] = 0;
this.currentBuffer[this.audioIndex++] = 0;
if (this.audioIndex == this.numSamplesTotal) {
this.audioIndex = 0;
this.audioHandle.writeAudio(this.currentBuffer);
Expand All @@ -5340,7 +5350,7 @@ GameBoyCore.prototype.generateAudio = function (numSamples) {
else {
while (--numSamples > -1) {
//MONO
this.currentBuffer[this.audioIndex++] = -1;
this.currentBuffer[this.audioIndex++] = 0;
if (this.audioIndex == this.numSamplesTotal) {
this.audioIndex = 0;
this.audioHandle.writeAudio(this.currentBuffer);
Expand Down Expand Up @@ -5707,15 +5717,15 @@ GameBoyCore.prototype.generateAudioSafe = function (tempBuffer, numSamples) {
while (--numSamples >= 0) {
//STEREO
this.audioChannelsComputeStereoSafe();
tempBuffer.push(this.currentSampleLeft * this.VinLeftChannelMasterVolume - 1);
tempBuffer.push(this.currentSampleRight * this.VinRightChannelMasterVolume - 1);
tempBuffer.push(this.highPass(this.currentSampleLeft * this.VinLeftChannelMasterVolume - 1));
tempBuffer.push(this.highPass(this.currentSampleRight * this.VinRightChannelMasterVolume - 1));
}
}
else {
while (--numSamples >= 0) {
//MONO
this.audioChannelsComputeMonoSafe();
tempBuffer.push(this.currentSampleRight * this.VinRightChannelMasterVolume - 1);
tempBuffer.push(this.highPass(this.currentSampleRight * this.VinRightChannelMasterVolume - 1));
}
}
}
Expand All @@ -5724,14 +5734,14 @@ GameBoyCore.prototype.generateAudioSafe = function (tempBuffer, numSamples) {
if (!settings[1]) {
while (--numSamples >= 0) {
//STEREO
tempBuffer.push(-1);
tempBuffer.push(-1);
tempBuffer.push(0);
tempBuffer.push(0);
}
}
else {
while (--numSamples >= 0) {
//MONO
tempBuffer.push(-1);
tempBuffer.push(0);
}
}
}
Expand Down

0 comments on commit 93e1bd6

Please sign in to comment.