mayhem-firmware/firmware/baseband/dsp_decimate.cpp

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/*
* Copyright (C) 2014 Jared Boone, ShareBrained Technology, Inc.
*
* This file is part of PortaPack.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2, or (at your option)
* any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; see the file COPYING. If not, write to
* the Free Software Foundation, Inc., 51 Franklin Street,
* Boston, MA 02110-1301, USA.
*/
#include "dsp_decimate.hpp"
#include <hal.h>
namespace dsp {
namespace decimate {
buffer_c16_t TranslateByFSOver4AndDecimateBy2CIC3::execute(buffer_c8_t src, buffer_c16_t dst) {
/* Translates incoming complex<int8_t> samples by -fs/4,
* decimates by two using a non-recursive third-order CIC filter.
*/
/* Derivation of algorithm:
* Original CIC filter (decimating by two):
* D_I0 = i3 * 1 + i2 * 3 + i1 * 3 + i0 * 1
* D_Q0 = q3 * 1 + q2 * 3 + q1 * 3 + q0 * 1
*
* D_I1 = i5 * 1 + i4 * 3 + i3 * 3 + i2 * 1
* D_Q1 = q5 * 1 + q4 * 3 + q3 * 3 + q2 * 1
*
* Translate -fs/4, phased 180 degrees, accomplished by complex multiplication
* of complex length-4 sequence:
*
* Substitute:
* i0 = -i0, q0 = -q0
* i1 = -q1, q1 = i1
* i2 = i2, q2 = q2
* i3 = q3, q3 = -i3
* i4 = -i4, q4 = -q4
* i5 = -q5, q5 = i5
*
* Resulting taps (with decimation by 2, four samples in, two samples out):
* D_I0 = q3 * 1 + i2 * 3 + -q1 * 3 + -i0 * 1
* D_Q0 = -i3 * 1 + q2 * 3 + i1 * 3 + -q0 * 1
*
* D_I1 = -q5 * 1 + -i4 * 3 + q3 * 3 + i2 * 1
* D_Q1 = i5 * 1 + -q4 * 3 + -i3 * 3 + q2 * 1
*/
// 6 cycles per complex input sample, not including loop overhead.
uint32_t q1_i0 = _q1_i0;
uint32_t q0_i1 = _q0_i1;
/* 3:1 Scaled by 32 to normalize output to +/-32768-ish. */
constexpr uint32_t scale_factor = 32;
const uint32_t k_3_1 = 0x00030001 * scale_factor;
uint32_t* src_p = reinterpret_cast<uint32_t*>(&src.p[0]);
uint32_t* const src_end = reinterpret_cast<uint32_t*>(&src.p[src.count]);
uint32_t* dst_p = reinterpret_cast<uint32_t*>(&dst.p[0]);
while(src_p < src_end) {
const uint32_t q3_i3_q2_i2 = *(src_p++); // 3
const uint32_t q5_i5_q4_i4 = *(src_p++);
const uint32_t i2_i3 = __SXTB16(q3_i3_q2_i2, 16); // 1: (q3_i3_q2_i2 ror 16)[23:16]:(q3_i3_q2_i2 ror 16)[7:0]
const uint32_t q3_q2 = __SXTB16(q3_i3_q2_i2, 8); // 1: (q3_i3_q2_i2 ror 8)[23:16]:(q3_i3_q2_i2 ror 8)[7:0]
const uint32_t i2_q3 = __PKHTB(i2_i3, q3_q2, 16); // 1: Rn[31:16]:(Rm>>16)[15:0]
const uint32_t i3_q2 = __PKHBT(q3_q2, i2_i3, 16); // 1:(Rm<<16)[31:16]:Rn[15:0]
// D_I0 = 3 * (i2 - q1) + (q3 - i0)
const uint32_t i2_m_q1_q3_m_i0 = __QSUB16(i2_q3, q1_i0); // 1: Rn[31:16]-Rm[31:16]:Rn[15:0]-Rm[15:0]
const uint32_t d_i0 = __SMUAD(k_3_1, i2_m_q1_q3_m_i0); // 1: Rm[15:0]*Rs[15:0]+Rm[31:16]*Rs[31:16]
// D_Q0 = 3 * (q2 + i1) - (i3 + q0)
const uint32_t i3_p_q0_q2_p_i1 = __QADD16(i3_q2, q0_i1); // 1: Rn[31:16]+Rm[31:16]:Rn[15:0]+Rm[15:0]
const uint32_t d_q0 = __SMUSDX(i3_p_q0_q2_p_i1, k_3_1); // 1: Rm[15:0]*Rs[31:16]Rm[31:16]*RsX[15:0]
const uint32_t d_q0_i0 = __PKHBT(d_i0, d_q0, 16); // 1: (Rm<<16)[31:16]:Rn[15:0]
const uint32_t i5_i4 = __SXTB16(q5_i5_q4_i4, 0); // 1: (q5_i5_q4_i4 ror 0)[23:16]:(q5_i5_q4_i4 ror 0)[7:0]
const uint32_t q4_q5 = __SXTB16(q5_i5_q4_i4, 24); // 1: (q5_i5_q4_i4 ror 24)[23:16]:(q5_i5_q4_i4 ror 24)[7:0]
const uint32_t q4_i5 = __PKHTB(q4_q5, i5_i4, 16); // 1: Rn[31:16]:(Rm>>16)[15:0]
const uint32_t q5_i4 = __PKHBT(i5_i4, q4_q5, 16); // 1: (Rm<<16)[31:16]:Rn[15:0]
// D_I1 = (i2 - q5) + 3 * (q3 - i4)
const uint32_t i2_m_q5_q3_m_i4 = __QSUB16(i2_q3, q5_i4); // 1: Rn[31:16]-Rm[31:16]:Rn[15:0]-Rm[15:0]
const uint32_t d_i1 = __SMUADX(i2_m_q5_q3_m_i4, k_3_1); // 1: Rm[15:0]*Rs[31:16]+Rm[31:16]*Rs[15:0]
// D_Q1 = (i5 + q2) - 3 * (q4 + i3)
const uint32_t q4_p_i3_i5_p_q2 = __QADD16(q4_i5, i3_q2); // 1: Rn[31:16]+Rm[31:16]:Rn[15:0]+Rm[15:0]
const uint32_t d_q1 = __SMUSD(k_3_1, q4_p_i3_i5_p_q2); // 1: Rm[15:0]*Rs[15:0]Rm[31:16]*Rs[31:16]
const uint32_t d_q1_i1 = __PKHBT(d_i1, d_q1, 16); // 1: (Rm<<16)[31:16]:Rn[15:0]
*(dst_p++) = d_q0_i0; // 3
*(dst_p++) = d_q1_i1;
q1_i0 = q5_i4;
q0_i1 = q4_i5;
}
_q1_i0 = q1_i0;
_q0_i1 = q0_i1;
return { dst.p, src.count / 2, src.sampling_rate / 2 };
}
buffer_c16_t DecimateBy2CIC3::execute(
buffer_c16_t src,
buffer_c16_t dst
) {
/* Complex non-recursive 3rd-order CIC filter (taps 1,3,3,1).
* Gain of 8.
* Consumes 16 bytes (4 s16:s16 samples) per loop iteration,
* Produces 8 bytes (2 s16:s16 samples) per loop iteration.
*/
uint32_t t1 = _iq0;
uint32_t t2 = _iq1;
uint32_t t3, t4;
const uint32_t taps = 0x00000003;
auto s = src.p;
auto d = dst.p;
const auto d_end = &dst.p[src.count / 2];
uint32_t i, q;
while(d < d_end) {
i = __SXTH(t1, 0); /* 1: I0 */
q = __SXTH(t1, 16); /* 1: Q0 */
i = __SMLABB(t2, taps, i); /* 1: I1*3 + I0 */
q = __SMLATB(t2, taps, q); /* 1: Q1*3 + Q0 */
t3 = *__SIMD32(s)++; /* 3: Q2:I2 */
t4 = *__SIMD32(s)++; /* Q3:I3 */
i = __SMLABB(t3, taps, i); /* 1: I2*3 + I1*3 + I0 */
q = __SMLATB(t3, taps, q); /* 1: Q2*3 + Q1*3 + Q0 */
int32_t si0 = __SXTAH(i, t4, 0); /* 1: I3 + Q2*3 + Q1*3 + Q0 */
int32_t sq0 = __SXTAH(q, t4, 16); /* 1: Q3 + Q2*3 + Q1*3 + Q0 */
i = __BFI(si0 / 8, sq0 / 8, 16, 16); /* 1: D2_Q0:D2_I0 */
*__SIMD32(d)++ = i; /* D2_Q0:D2_I0 */
i = __SXTH(t3, 0); /* 1: I2 */
q = __SXTH(t3, 16); /* 1: Q2 */
i = __SMLABB(t4, taps, i); /* 1: I3*3 + I2 */
q = __SMLATB(t4, taps, q); /* 1: Q3*3 + Q2 */
t1 = *__SIMD32(s)++; /* 3: Q4:I4 */
t2 = *__SIMD32(s)++; /* Q5:I5 */
i = __SMLABB(t1, taps, i); /* 1: I4*3 + I3*3 + I2 */
q = __SMLATB(t1, taps, q); /* 1: Q4*3 + Q3*3 + Q2 */
int32_t si1 = __SXTAH(i, t2, 0) ; /* 1: I5 + Q4*3 + Q3*3 + Q2 */
int32_t sq1 = __SXTAH(q, t2, 16); /* 1: Q5 + Q4*3 + Q3*3 + Q2 */
i = __BFI(si1 / 8, sq1 / 8, 16, 16); /* 1: D2_Q1:D2_I1 */
*__SIMD32(d)++ = i; /* D2_Q1:D2_I1 */
}
_iq0 = t1;
_iq1 = t2;
return { dst.p, src.count / 2, src.sampling_rate / 2 };
}
buffer_s16_t FIR64AndDecimateBy2Real::execute(
buffer_s16_t src,
buffer_s16_t dst
) {
/* int16_t input (sample count "n" must be multiple of 4)
* -> int16_t output, decimated by 2.
* taps are normalized to 1 << 16 == 1.0.
*/
auto src_p = src.p;
auto dst_p = dst.p;
int32_t n = src.count;
for(; n>0; n-=2) {
z[taps_count-2] = *(src_p++);
z[taps_count-1] = *(src_p++);
int32_t t = 0;
for(size_t j=0; j<taps_count; j+=4) {
t += z[j+0] * taps[j+0];
t += z[j+1] * taps[j+1];
t += z[j+2] * taps[j+2];
t += z[j+3] * taps[j+3];
z[j+0] = z[j+0+2];
z[j+1] = z[j+1+2];
z[j+2] = z[j+2+2];
z[j+3] = z[j+3+2];
}
*(dst_p++) = t / 65536;
}
return { dst.p, src.count / 2, src.sampling_rate / 2 };
}
size_t fir_and_decimate_by_2_complex_fast(
const complex16_t* const src_start,
const size_t src_count,
complex16_t* const dst_start,
complex16_t* const z,
const complex16_t* const taps,
const size_t taps_count,
const size_t decimation_factor
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) {
/* int16_t input (sample count "n" must be multiple of decimation_factor)
* -> int16_t output, decimated by decimation_factor.
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* taps are normalized to 1 << 16 == 1.0.
*/
const auto src_p = src_start;
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auto dst_p = dst_start;
while(src_p < &src_start[src_count]) {
/* Put two new samples into delay buffer */
auto z_new_p = &z[taps_count - decimation_factor];
for(size_t i=0; i<decimation_factor; i++) {
*__SIMD32(z_new_p)++ = *__SIMD32(src_p)++;
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}
size_t loop_count = taps_count / 8;
auto t_p = &taps[0];
auto z_p = &z[0];
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int64_t t_real = 0;
int64_t t_imag = 0;
while(loop_count > 0) {
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const auto tap0 = *__SIMD32(t_p)++;
const auto sample0 = *__SIMD32(z_p)++;
const auto tap1 = *__SIMD32(t_p)++;
const auto sample1 = *__SIMD32(z_p)++;
t_real = __SMLSLD(sample0, tap0, t_real);
t_imag = __SMLALDX(sample0, tap0, t_imag);
t_real = __SMLSLD(sample1, tap1, t_real);
t_imag = __SMLALDX(sample1, tap1, t_imag);
const auto tap2 = *__SIMD32(t_p)++;
const auto sample2 = *__SIMD32(z_p)++;
const auto tap3 = *__SIMD32(t_p)++;
const auto sample3 = *__SIMD32(z_p)++;
t_real = __SMLSLD(sample2, tap2, t_real);
t_imag = __SMLALDX(sample2, tap2, t_imag);
t_real = __SMLSLD(sample3, tap3, t_real);
t_imag = __SMLALDX(sample3, tap3, t_imag);
const auto tap4 = *__SIMD32(t_p)++;
const auto sample4 = *__SIMD32(z_p)++;
const auto tap5 = *__SIMD32(t_p)++;
const auto sample5 = *__SIMD32(z_p)++;
t_real = __SMLSLD(sample4, tap4, t_real);
t_imag = __SMLALDX(sample4, tap4, t_imag);
t_real = __SMLSLD(sample5, tap5, t_real);
t_imag = __SMLALDX(sample5, tap5, t_imag);
const auto tap6 = *__SIMD32(t_p)++;
const auto sample6 = *__SIMD32(z_p)++;
const auto tap7 = *__SIMD32(t_p)++;
const auto sample7 = *__SIMD32(z_p)++;
t_real = __SMLSLD(sample6, tap6, t_real);
t_imag = __SMLALDX(sample6, tap6, t_imag);
t_real = __SMLSLD(sample7, tap7, t_real);
t_imag = __SMLALDX(sample7, tap7, t_imag);
loop_count--;
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}
/* TODO: Re-evaluate whether saturation is performed, normalization,
* all that jazz.
*/
const int32_t r = t_real >> 16;
const int32_t i = t_imag >> 16;
const int32_t r_sat = __SSAT(r, 16);
const int32_t i_sat = __SSAT(i, 16);
*__SIMD32(dst_p)++ = __PKHBT(
r_sat,
i_sat,
16
);
/* Shift sample buffer left/down by decimation factor. */
const size_t unroll_factor = 4;
size_t shift_count = (taps_count - 1) / unroll_factor;
auto t = &z[0];
auto s = &z[decimation_factor];
while(shift_count > 0) {
*__SIMD32(t)++ = *__SIMD32(s)++;
*__SIMD32(t)++ = *__SIMD32(s)++;
*__SIMD32(t)++ = *__SIMD32(s)++;
*__SIMD32(t)++ = *__SIMD32(s)++;
shift_count--;
}
shift_count = (taps_count - 1) % unroll_factor;
while(shift_count > 0) {
*(t++) = *(s++);
shift_count--;
}
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}
return src_count / decimation_factor;
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}
buffer_s16_t DecimateBy2CIC4Real::execute(
buffer_s16_t src,
buffer_s16_t dst
) {
auto src_p = src.p;
auto dst_p = dst.p;
int32_t n = src.count;
for(; n>0; n-=2) {
/* TODO: Probably a lot of room to optimize... */
z[0] = z[2];
z[1] = z[3];
z[2] = z[4];
z[3] = *(src_p++);
z[4] = *(src_p++);
int32_t t = z[0] + z[1] * 4 + z[2] * 6 + z[3] * 4 + z[4];
*(dst_p++) = t / 16;
}
return { dst.p, src.count / 2, src.sampling_rate / 2 };
}
#if 0
buffer_c16_t DecimateBy2HBF5Complex::execute(
buffer_c16_t const src,
buffer_c16_t const dst
) {
auto src_p = src.p;
auto dst_p = dst.p;
int32_t n = src.count;
for(; n>0; n-=2) {
/* TODO: Probably a lot of room to optimize... */
z[0] = z[2];
//z[1] = z[3];
z[2] = z[4];
//z[3] = z[5];
z[4] = z[6];
z[5] = z[7];
z[6] = z[8];
z[7] = z[9];
z[8] = z[10];
z[9] = *(src_p++);
z[10] = *(src_p++);
int32_t t_real { z[5].real * 256 };
int32_t t_imag { z[5].imag * 256 };
t_real += (z[ 0].real + z[10].real) * 3;
t_imag += (z[ 0].imag + z[10].imag) * 3;
t_real -= (z[ 2].real + z[ 8].real) * 25;
t_imag -= (z[ 2].imag + z[ 8].imag) * 25;
t_real += (z[ 4].real + z[ 6].real) * 150;
t_imag += (z[ 4].imag + z[ 6].imag) * 150;
*(dst_p++) = { t_real / 256, t_imag / 256 };
}
return { dst.p, src.count / 2, src.sampling_rate / 2 };
}
buffer_c16_t DecimateBy2HBF7Complex::execute(
buffer_c16_t const src,
buffer_c16_t const dst
) {
auto src_p = src.p;
auto dst_p = dst.p;
int32_t n = src.count;
for(; n>0; n-=2) {
/* TODO: Probably a lot of room to optimize... */
z[0] = z[2];
//z[1] = z[3];
z[2] = z[4];
//z[3] = z[5];
z[4] = z[6];
z[5] = z[7];
z[6] = z[8];
z[7] = z[9];
z[8] = z[10];
z[9] = *(src_p++);
z[10] = *(src_p++);
int32_t t_real { z[5].real * 512 };
int32_t t_imag { z[5].imag * 512 };
t_real += (z[ 0].real + z[10].real) * 7;
t_imag += (z[ 0].imag + z[10].imag) * 7;
t_real -= (z[ 2].real + z[ 8].real) * 53;
t_imag -= (z[ 2].imag + z[ 8].imag) * 53;
t_real += (z[ 4].real + z[ 6].real) * 302;
t_imag += (z[ 4].imag + z[ 6].imag) * 302;
*(dst_p++) = { t_real / 512, t_imag / 512 };
}
return { dst.p, src.count / 2, src.sampling_rate / 2 };
}
#endif
} /* namespace decimate */
} /* namespace dsp */