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Use fixed point arithmetic with s16 biquads.

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This commit is contained in:
David Reid
2020-01-29 18:50:50 +10:00
parent 02df9b2e9a
commit c8b6fdaf2c
1 changed files with 38 additions and 21 deletions
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research/ma_lpf.h
+38 -21
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@@ -145,6 +145,15 @@ ma_uint32 ma_lpf_get_latency(ma_lpf* pLPF);
#if defined(MINIAUDIO_IMPLEMENTATION)
#ifndef MA_BIQUAD_FIXED_POINT_SHIFT
#define MA_BIQUAD_FIXED_POINT_SHIFT 14
#endif
static ma_int32 ma_biquad_float_to_fp(double x)
{
return (ma_int32)(x * (1 << MA_BIQUAD_FIXED_POINT_SHIFT));
}
ma_biquad_config ma_biquad_config_init(ma_format format, ma_uint32 channels, double a0, double a1, double a2, double b0, double b1, double b2)
{
ma_biquad_config config;
@@ -196,11 +205,19 @@ ma_result ma_biquad_reinit(const ma_biquad_config* pConfig, ma_biquad* pBQ)
pBQ->channels = pConfig->channels;
/* Normalize. */
pBQ->a1.f32 = (float)(pConfig->a1 / pConfig->a0);
pBQ->a2.f32 = (float)(pConfig->a2 / pConfig->a0);
pBQ->b0.f32 = (float)(pConfig->b0 / pConfig->a0);
pBQ->b1.f32 = (float)(pConfig->b1 / pConfig->a0);
pBQ->b2.f32 = (float)(pConfig->b2 / pConfig->a0);
if (pConfig->format == ma_format_f32) {
pBQ->a1.f32 = (float)(pConfig->a1 / pConfig->a0);
pBQ->a2.f32 = (float)(pConfig->a2 / pConfig->a0);
pBQ->b0.f32 = (float)(pConfig->b0 / pConfig->a0);
pBQ->b1.f32 = (float)(pConfig->b1 / pConfig->a0);
pBQ->b2.f32 = (float)(pConfig->b2 / pConfig->a0);
} else {
pBQ->a1.s32 = ma_biquad_float_to_fp(pConfig->a1 / pConfig->a0);
pBQ->a2.s32 = ma_biquad_float_to_fp(pConfig->a2 / pConfig->a0);
pBQ->b0.s32 = ma_biquad_float_to_fp(pConfig->b0 / pConfig->a0);
pBQ->b1.s32 = ma_biquad_float_to_fp(pConfig->b1 / pConfig->a0);
pBQ->b2.s32 = ma_biquad_float_to_fp(pConfig->b2 / pConfig->a0);
}
return MA_SUCCESS;
}
@@ -233,25 +250,25 @@ static MA_INLINE void ma_biquad_process_pcm_frame_f32__direct_form_2_transposed(
static MA_INLINE void ma_biquad_process_pcm_frame_s16__direct_form_2_transposed(ma_biquad* pBQ, ma_int16* pY, const ma_int16* pX)
{
ma_uint32 c;
const float a1 = pBQ->a1.f32;
const float a2 = pBQ->a2.f32;
const float b0 = pBQ->b0.f32;
const float b1 = pBQ->b1.f32;
const float b2 = pBQ->b2.f32;
const ma_int32 a1 = pBQ->a1.s32;
const ma_int32 a2 = pBQ->a2.s32;
const ma_int32 b0 = pBQ->b0.s32;
const ma_int32 b1 = pBQ->b1.s32;
const ma_int32 b2 = pBQ->b2.s32;
for (c = 0; c < pBQ->channels; c += 1) {
float r1 = pBQ->r1[c].f32;
float r2 = pBQ->r2[c].f32;
float x = pX[c] / 32767.0f; /* s16 -> f32 */
float y;
ma_int32 r1 = pBQ->r1[c].s32;
ma_int32 r2 = pBQ->r2[c].s32;
ma_int32 x = pX[c];
ma_int32 y;
y = b0*x + r1;
r1 = b1*x - a1*y + r2;
r2 = b2*x - a2*y;
y = (b0*x + r1) >> MA_BIQUAD_FIXED_POINT_SHIFT;
r1 = (b1*x - a1*y + r2);
r2 = (b2*x - a2*y);
pY[c] = (ma_int16)ma_clamp((ma_int32)(y * 32767.0f), -32768, 32767); /* f32 -> s16 */
pBQ->r1[c].f32 = r1;
pBQ->r2[c].f32 = r2;
pY[c] = (ma_int16)ma_clamp(y, -32768, 32767);
pBQ->r1[c].s32 = r1;
pBQ->r2[c].s32 = r2;
}
}
@@ -270,7 +287,7 @@ ma_result ma_biquad_process_pcm_frames(ma_biquad* pBQ, void* pFramesOut, const v
const float* pX = (const float*)pFramesIn;
for (n = 0; n < frameCount; n += 1) {
ma_biquad_process_pcm_frame_f32__direct_form_2_transposed(pBQ, pY + n*pBQ->channels, pX + n*pBQ->channels);
ma_biquad_process_pcm_frame_f32__direct_form_2_transposed(pBQ, pY, pX);
pY += pBQ->channels;
pX += pBQ->channels;
}