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dcfilter: more correct algorithm. doesn't sound any different. speed unchanged.

This commit is contained in:
goyuken 2012-12-09 20:02:43 +00:00
parent 34a6248606
commit b9f37d7ed8
2 changed files with 30 additions and 19 deletions
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4
BizHawk.Emulation/Consoles/Nintendo/Gameboy/Gambatte.cs
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@ -738,7 +738,9 @@ namespace BizHawk.Emulation.Consoles.GB
void InitSound()
{
resampler = new Sound.Utilities.SpeexResampler(2, 2097152, 44100, 2097152, 44100, null, this);
dcfilter = Sound.Utilities.DCFilter.AsISyncSoundProvider(resampler, 65536);
//dcfilter = Sound.Utilities.DCFilter.AsISyncSoundProvider(resampler, 65536);
// lowpass filtering on an actual GB was probably pretty aggressive?
dcfilter = Sound.Utilities.DCFilter.AsISyncSoundProvider(resampler, 2048);
}
void DisposeSound()

45
BizHawk.Emulation/Sound/Utilities/DCFilter.cs
View File

@ -20,10 +20,21 @@ namespace BizHawk.Emulation.Sound.Utilities
ISoundProvider input;
ISyncSoundProvider syncinput;
int sumL = 0;
int sumR = 0;
int latchL = 0;
int latchR = 0;
int accumL = 0;
int accumR = 0;
Queue<short> buffer;
static int DepthFromFilterwidth(int filterwidth)
{
int ret = -2;
while (filterwidth > 0)
{
filterwidth >>= 1;
ret++;
}
return ret;
}
int depth;
@ -48,14 +59,11 @@ namespace BizHawk.Emulation.Sound.Utilities
DCFilter(ISoundProvider input, ISyncSoundProvider syncinput, int filterwidth)
{
if (filterwidth < 1 || filterwidth > 65536)
if (filterwidth < 8 || filterwidth > 65536)
throw new ArgumentOutOfRangeException();
this.input = input;
this.syncinput = syncinput;
depth = filterwidth;
buffer = new Queue<short>(depth * 2);
for (int i = 0; i < depth * 2; i++)
buffer.Enqueue(0);
depth = DepthFromFilterwidth(filterwidth);
}
/// <summary>
@ -72,16 +80,17 @@ namespace BizHawk.Emulation.Sound.Utilities
{
for (int i = 0; i < length; i += 2)
{
sumL -= buffer.Dequeue();
sumR -= buffer.Dequeue();
short L = samplesin[i];
short R = samplesin[i + 1];
sumL += L;
sumR += R;
buffer.Enqueue(L);
buffer.Enqueue(R);
int bigL = L - sumL / depth;
int bigR = R - sumR / depth;
int L = samplesin[i] << 12;
int R = samplesin[i + 1] << 12;
accumL -= accumL >> depth;
accumR -= accumR >> depth;
accumL += L - latchL;
accumR += R - latchR;
latchL = L;
latchR = R;
int bigL = accumL >> 12;
int bigR = accumR >> 12;
// check for clipping
if (bigL > 32767)
samplesout[i] = 32767;