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Add function for c8->c16 decimate by two without fs/4 shift.
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@ -26,6 +26,63 @@
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namespace dsp {
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namespace decimate {
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buffer_c16_t Complex8DecimateBy2CIC3::execute(buffer_c8_t src, buffer_c16_t dst) {
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/* Decimates by two using a non-recursive third-order CIC filter.
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*/
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/* CIC filter (decimating by two):
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* D_I0 = i3 * 1 + i2 * 3 + i1 * 3 + i0 * 1
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* D_Q0 = q3 * 1 + q2 * 3 + q1 * 3 + q0 * 1
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*
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* D_I1 = i5 * 1 + i4 * 3 + i3 * 3 + i2 * 1
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* D_Q1 = q5 * 1 + q4 * 3 + q3 * 3 + q2 * 1
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*/
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uint32_t i1_i0 = _i1_i0;
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uint32_t q1_q0 = _q1_q0;
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/* 3:1 Scaled by 32 to normalize output to +/-32768-ish. */
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constexpr uint32_t scale_factor = 32;
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constexpr uint32_t k_3_1 = 0x00030001 * scale_factor;
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uint32_t* src_p = reinterpret_cast<uint32_t*>(&src.p[0]);
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uint32_t* const src_end = reinterpret_cast<uint32_t*>(&src.p[src.count]);
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uint32_t* dst_p = reinterpret_cast<uint32_t*>(&dst.p[0]);
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while(src_p < src_end) {
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const uint32_t q3_i3_q2_i2 = *(src_p++); // 3
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const uint32_t q5_i5_q4_i4 = *(src_p++);
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const uint32_t d_i0_partial = __SMUAD(k_3_1, i1_i0); // 1: = 3 * i1 + 1 * i0
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const uint32_t i3_i2 = __SXTB16(q3_i3_q2_i2, 0); // 1: (q3_i3_q2_i2 ror 0)[23:16]:(q3_i3_q2_i2 ror 0)[7:0]
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const uint32_t d_i0 = __SMLADX(k_3_1, i3_i2, d_i0_partial); // 1: + 3 * i2 + 1 * i3
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const uint32_t d_q0_partial = __SMUAD(k_3_1, q1_q0); // 1: = 3 * q1 * 1 * q0
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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]
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const uint32_t d_q0 = __SMLADX(k_3_1, q3_q2, d_q0_partial); // 1: + 3 * q2 + 1 * q3
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const uint32_t d_q0_i0 = __PKHBT(d_i0, d_q0, 16); // 1: (Rm<<16)[31:16]:Rn[15:0]
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const uint32_t d_i1_partial = __SMUAD(k_3_1, i3_i2); // 1: = 3 * i3 + 1 * i2
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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]
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const uint32_t d_i1 = __SMLADX(k_3_1, i5_i4, d_i1_partial); // 1: + 1 * i5 + 3 * i4
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const uint32_t d_q1_partial = __SMUAD(k_3_1, q3_q2); // 1: = 3 * q3 * 1 * q2
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const uint32_t q5_q4 = __SXTB16(q5_i5_q4_i4, 8); // 1: (q5_i5_q4_i4 ror 8)[23:16]:(q5_i5_q4_i4 ror 8)[7:0]
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const uint32_t d_q1 = __SMLADX(k_3_1, q5_q4, d_q1_partial); // 1: + 1 * q5 + 3 * q4
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const uint32_t d_q1_i1 = __PKHBT(d_i1, d_q1, 16); // 1: (Rm<<16)[31:16]:Rn[15:0]
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*(dst_p++) = d_q0_i0; // 3
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*(dst_p++) = d_q1_i1;
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i1_i0 = i5_i4;
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q1_q0 = q5_q4;
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}
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_i1_i0 = i1_i0;
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_q1_q0 = q1_q0;
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return { dst.p, src.count / 2, src.sampling_rate / 2 };
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}
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buffer_c16_t TranslateByFSOver4AndDecimateBy2CIC3::execute(buffer_c8_t src, buffer_c16_t dst) {
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/* Translates incoming complex<int8_t> samples by -fs/4,
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* decimates by two using a non-recursive third-order CIC filter.
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@ -34,6 +34,18 @@
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namespace dsp {
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namespace decimate {
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class Complex8DecimateBy2CIC3 {
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public:
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buffer_c16_t execute(
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buffer_c8_t src,
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buffer_c16_t dst
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);
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private:
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uint32_t _i1_i0 { 0 };
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uint32_t _q1_q0 { 0 };
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};
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class TranslateByFSOver4AndDecimateBy2CIC3 {
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public:
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buffer_c16_t execute(
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