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Add an all-pass filter that replicates the band splitter's phase shift

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This commit is contained in:
Chris Robinson 2017-07-19 02:48:01 -07:00
parent 0135ddc2e5
commit fea74124c8
2 changed files with 51 additions and 0 deletions
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39
Alc/bformatdec.c
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@ -75,6 +75,45 @@ void bandsplit_process(BandSplitter *splitter, ALfloat *restrict hpout, ALfloat
}
void splitterap_init(SplitterAllpass *splitter, ALfloat freq_mult)
{
ALfloat w = freq_mult * F_TAU;
ALfloat cw = cosf(w);
if(cw > FLT_EPSILON)
splitter->coeff = (sinf(w) - 1.0f) / cw;
else
splitter->coeff = cw * -0.5f;
splitter->z1 = 0.0f;
}
void splitterap_clear(SplitterAllpass *splitter)
{
splitter->z1 = 0.0f;
}
void splitterap_process(SplitterAllpass *splitter, ALfloat *restrict samples, ALsizei count)
{
ALfloat coeff, d, x;
ALfloat z1;
ALsizei i;
coeff = splitter->coeff;
z1 = splitter->z1;
for(i = 0;i < count;i++)
{
x = samples[i];
d = x - coeff*z1;
x = z1 + coeff*d;
z1 = d;
samples[i] = x;
}
splitter->z1 = z1;
}
static const ALfloat UnitScale[MAX_AMBI_COEFFS] = {
1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f,
1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f

12
Alc/bformatdec.h
View File

@ -60,4 +60,16 @@ void bandsplit_clear(BandSplitter *splitter);
void bandsplit_process(BandSplitter *splitter, ALfloat *restrict hpout, ALfloat *restrict lpout,
const ALfloat *input, ALsizei count);
/* The all-pass portion of the band splitter. Applies the same phase shift
* without splitting the signal.
*/
typedef struct SplitterAllpass {
ALfloat coeff;
ALfloat z1;
} SplitterAllpass;
void splitterap_init(SplitterAllpass *splitter, ALfloat freq_mult);
void splitterap_clear(SplitterAllpass *splitter);
void splitterap_process(SplitterAllpass *splitter, ALfloat *restrict samples, ALsizei count);
#endif /* BFORMATDEC_H */