kcat/openal-soft
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Implement an alternative low-pass filter

Browse Source 
This method samples from the buffer so that it gets a time-correct 5khz stream,
which is subtracted from the original sample and has the high-frequency gain
applied, then added back.
A better method may be to average all the samples from the current one to the
one freq/5000 away, instead of bilinear filtering the two nearest freq/5000
apart. Processing cost will need to determine its viability
This commit is contained in:
Chris Robinson 2008-07-23 22:29:53 -07:00
parent d45b1207d0
commit a75e75aef5
2 changed files with 32 additions and 39 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

68
Alc/ALu.c
View File

@ -210,20 +210,9 @@ static __inline ALvoid aluMatrixVector(ALfloat *vector,ALfloat matrix[3][3])
memcpy(vector, result, sizeof(result));
}
static __inline ALfloat aluComputeSample(ALfloat GainHF, ALfloat sample, ALfloat LastSample)
static __inline ALfloat aluComputeSample(ALfloat GainHF, ALfloat sample, ALfloat LowSample)
{
if(GainHF < 1.0f)
{
if(GainHF > 0.0f)
{
sample *= GainHF;
sample += LastSample * (1.0f-GainHF);
}
else
sample = 0.0f;
}
return sample;
return LowSample + ((sample - LowSample) * GainHF);
}
static ALvoid CalcSourceParams(ALCcontext *ALContext, ALsource *ALSource,
@ -603,11 +592,13 @@ ALvoid aluMixData(ALCcontext *ALContext,ALvoid *buffer,ALsizei size,ALenum forma
ALuint BlockAlign,BufferSize;
ALuint DataSize=0,DataPosInt=0,DataPosFrac=0;
ALuint Channels,Frequency,ulExtraSamples;
ALfloat DrySample, WetSample;
ALboolean doReverb;
ALfloat Pitch;
ALint Looping,increment,State;
ALuint Buffer,fraction;
ALint Looping,State;
ALint fraction,increment;
ALint LowFrac;
ALuint LowStep;
ALuint Buffer;
ALuint SamplesToDo;
ALsource *ALSource;
ALbuffer *ALBuffer;
@ -676,8 +667,6 @@ ALvoid aluMixData(ALCcontext *ALContext,ALvoid *buffer,ALsizei size,ALenum forma
//Get source info
DataPosInt = ALSource->position;
DataPosFrac = ALSource->position_fraction;
DrySample = ALSource->LastDrySample;
WetSample = ALSource->LastWetSample;
//Compute 18.14 fixed point step
increment = (ALint)(Pitch*(ALfloat)(1L<<FRACTIONBITS));
@ -722,36 +711,45 @@ ALvoid aluMixData(ALCcontext *ALContext,ALvoid *buffer,ALsizei size,ALenum forma
BufferSize = min(BufferSize, (SamplesToDo-j));
//Actual sample mixing loop
LowStep = Frequency/5000;
if(LowStep < 1) LowStep = 1;
if(LowStep > 8) LowStep = 8;
Data += DataPosInt*Channels;
while(BufferSize--)
{
k = DataPosFrac>>FRACTIONBITS;
fraction = DataPosFrac&FRACTIONMASK;
LowFrac = ((DataPosFrac+(DataPosInt<<FRACTIONBITS))/LowStep)&FRACTIONMASK;
if(Channels==1)
{
ALfloat sample, lowsamp, outsamp;
//First order interpolator
ALfloat sample = (ALfloat)((ALshort)(((Data[k]*((1L<<FRACTIONBITS)-fraction))+(Data[k+1]*(fraction)))>>FRACTIONBITS));
sample = (Data[k]*((1<<FRACTIONBITS)-fraction) +
Data[k+1]*fraction) >> FRACTIONBITS;
lowsamp = (Data[((k+DataPosInt)/LowStep )*LowStep - DataPosInt]*((1<<FRACTIONBITS)-LowFrac) +
Data[((k+DataPosInt)/LowStep + 1)*LowStep - DataPosInt]*LowFrac) >>
FRACTIONBITS;
//Direct path final mix buffer and panning
DrySample = aluComputeSample(DryGainHF, sample, DrySample);
DryBuffer[j][FRONT_LEFT] += DrySample*DrySend[FRONT_LEFT];
DryBuffer[j][FRONT_RIGHT] += DrySample*DrySend[FRONT_RIGHT];
DryBuffer[j][SIDE_LEFT] += DrySample*DrySend[SIDE_LEFT];
DryBuffer[j][SIDE_RIGHT] += DrySample*DrySend[SIDE_RIGHT];
DryBuffer[j][BACK_LEFT] += DrySample*DrySend[BACK_LEFT];
DryBuffer[j][BACK_RIGHT] += DrySample*DrySend[BACK_RIGHT];
outsamp = aluComputeSample(DryGainHF, sample, lowsamp);
DryBuffer[j][FRONT_LEFT] += outsamp*DrySend[FRONT_LEFT];
DryBuffer[j][FRONT_RIGHT] += outsamp*DrySend[FRONT_RIGHT];
DryBuffer[j][SIDE_LEFT] += outsamp*DrySend[SIDE_LEFT];
DryBuffer[j][SIDE_RIGHT] += outsamp*DrySend[SIDE_RIGHT];
DryBuffer[j][BACK_LEFT] += outsamp*DrySend[BACK_LEFT];
DryBuffer[j][BACK_RIGHT] += outsamp*DrySend[BACK_RIGHT];
//Room path final mix buffer and panning
WetSample = aluComputeSample(WetGainHF, sample, WetSample);
outsamp = aluComputeSample(WetGainHF, sample, lowsamp);
if(doReverb)
ReverbBuffer[j] += WetSample;
ReverbBuffer[j] += outsamp;
else
{
WetBuffer[j][FRONT_LEFT] += WetSample*WetSend[FRONT_LEFT];
WetBuffer[j][FRONT_RIGHT] += WetSample*WetSend[FRONT_RIGHT];
WetBuffer[j][SIDE_LEFT] += WetSample*WetSend[SIDE_LEFT];
WetBuffer[j][SIDE_RIGHT] += WetSample*WetSend[SIDE_RIGHT];
WetBuffer[j][BACK_LEFT] += WetSample*WetSend[BACK_LEFT];
WetBuffer[j][BACK_RIGHT] += WetSample*WetSend[BACK_RIGHT];
WetBuffer[j][FRONT_LEFT] += outsamp*WetSend[FRONT_LEFT];
WetBuffer[j][FRONT_RIGHT] += outsamp*WetSend[FRONT_RIGHT];
WetBuffer[j][SIDE_LEFT] += outsamp*WetSend[SIDE_LEFT];
WetBuffer[j][SIDE_RIGHT] += outsamp*WetSend[SIDE_RIGHT];
WetBuffer[j][BACK_LEFT] += outsamp*WetSend[BACK_LEFT];
WetBuffer[j][BACK_RIGHT] += outsamp*WetSend[BACK_RIGHT];
}
}
else
@ -826,8 +824,6 @@ ALvoid aluMixData(ALCcontext *ALContext,ALvoid *buffer,ALsizei size,ALenum forma
//Update source info
ALSource->position = DataPosInt;
ALSource->position_fraction = DataPosFrac;
ALSource->LastDrySample = DrySample;
ALSource->LastWetSample = WetSample;
}
//Handle looping sources

3
OpenAL32/Include/alSource.h
View File

@ -70,9 +70,6 @@ typedef struct ALsource
ALfilter WetFilter;
} Send[MAX_SENDS];
ALfloat LastDrySample;
ALfloat LastWetSample;
ALboolean DryGainHFAuto;
ALboolean WetGainAuto;
ALboolean WetGainHFAuto;