299 lines
8.6 KiB
C++
299 lines
8.6 KiB
C++
/*****************************************************************************
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Downsampler2xNeon.hpp
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Author: Laurent de Soras, 2016
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--- Legal stuff ---
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This program is free software. It comes without any warranty, to
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the extent permitted by applicable law. You can redistribute it
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and/or modify it under the terms of the Do What The Fuck You Want
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To Public License, Version 2, as published by Sam Hocevar. See
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http://sam.zoy.org/wtfpl/COPYING for more details.
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*Tab=3***********************************************************************/
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#if ! defined (hiir_Downsampler2xNeon_CODEHEADER_INCLUDED)
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#define hiir_Downsampler2xNeon_CODEHEADER_INCLUDED
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/*\\\ INCLUDE FILES \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\*/
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#include "hiir/StageProcNeon.h"
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#include <arm_neon.h>
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#include <cassert>
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namespace hiir
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{
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/*\\\ PUBLIC \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\*/
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/*
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==============================================================================
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Name: ctor
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Throws: Nothing
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==============================================================================
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*/
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template <int NC>
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Downsampler2xNeon <NC>::Downsampler2xNeon ()
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: _filter ()
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{
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for (int i = 0; i < NBR_STAGES + 1; ++i)
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{
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_filter [i]._mem4 = vdupq_n_f32 (0);
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}
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if ((NBR_COEFS & 1) != 0)
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{
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const int pos = (NBR_COEFS ^ 1) & (STAGE_WIDTH - 1);
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_filter [NBR_STAGES]._coef [pos] = 1;
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}
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clear_buffers ();
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}
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/*
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==============================================================================
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Name: set_coefs
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Description:
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Sets filter coefficients. Generate them with the PolyphaseIir2Designer
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class.
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Call this function before doing any processing.
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Input parameters:
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- coef_arr: Array of coefficients. There should be as many coefficients as
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mentioned in the class template parameter.
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Throws: Nothing
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==============================================================================
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*/
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template <int NC>
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void Downsampler2xNeon <NC>::set_coefs (const double coef_arr [])
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{
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assert (coef_arr != 0);
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for (int i = 0; i < NBR_COEFS; ++i)
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{
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const int stage = (i / STAGE_WIDTH) + 1;
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const int pos = (i ^ 1) & (STAGE_WIDTH - 1);
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_filter [stage]._coef [pos] = float (coef_arr [i]);
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}
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}
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/*
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==============================================================================
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Name: process_sample
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Description:
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Downsamples (x2) one pair of samples, to generate one output sample.
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Input parameters:
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- in_ptr: pointer on the two samples to decimate
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Returns: Samplerate-reduced sample.
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Throws: Nothing
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==============================================================================
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*/
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template <int NC>
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float Downsampler2xNeon <NC>::process_sample (const float in_ptr [2])
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{
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assert (in_ptr != 0);
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// Combines two input samples and two mid-processing data
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const float32x2_t spl_in = vreinterpret_f32_u8 (
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vld1_u8 (reinterpret_cast <const uint8_t *> (in_ptr))
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);
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const float32x2_t spl_mid = vget_low_f32 (_filter [NBR_STAGES]._mem4);
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float32x4_t y = vcombine_f32 (spl_in, spl_mid);
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float32x4_t mem = _filter [0]._mem4;
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// Processes each stage
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StageProcNeon <NBR_STAGES>::process_sample_pos (&_filter [0], y, mem);
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_filter [NBR_STAGES]._mem4 = y;
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// Averages both paths and outputs the result
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const float out_0 = vgetq_lane_f32 (y, 3);
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const float out_1 = vgetq_lane_f32 (y, 2);
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const float out = (out_0 + out_1) * 0.5f;
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return out;
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}
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/*
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==============================================================================
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Name: process_block
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Description:
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Downsamples (x2) a block of samples.
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Input and output blocks may overlap, see assert() for details.
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Input parameters:
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- in_ptr: Input array, containing nbr_spl * 2 samples.
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- nbr_spl: Number of samples to output, > 0
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Output parameters:
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- out_ptr: Array for the output samples, capacity: nbr_spl samples.
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Throws: Nothing
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==============================================================================
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*/
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template <int NC>
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void Downsampler2xNeon <NC>::process_block (float out_ptr [], const float in_ptr [], long nbr_spl)
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{
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assert (in_ptr != 0);
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assert (out_ptr != 0);
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assert (out_ptr <= in_ptr || out_ptr >= in_ptr + nbr_spl * 2);
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assert (nbr_spl > 0);
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long pos = 0;
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do
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{
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out_ptr [pos] = process_sample (in_ptr + pos * 2);
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++ pos;
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}
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while (pos < nbr_spl);
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}
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/*
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==============================================================================
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Name: process_sample_split
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Description:
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Split (spectrum-wise) in half a pair of samples. The lower part of the
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spectrum is a classic downsampling, equivalent to the output of
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process_sample().
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The higher part is the complementary signal: original filter response
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is flipped from left to right, becoming a high-pass filter with the same
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cutoff frequency. This signal is then critically sampled (decimation by 2),
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flipping the spectrum: Fs/4...Fs/2 becomes Fs/4...0.
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Input parameters:
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- in_ptr: pointer on the pair of input samples
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Output parameters:
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- low: output sample, lower part of the spectrum (downsampling)
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- high: output sample, higher part of the spectrum.
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Throws: Nothing
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==============================================================================
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*/
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template <int NC>
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void Downsampler2xNeon <NC>::process_sample_split (float &low, float &high, const float in_ptr [2])
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{
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assert (in_ptr != 0);
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// Combines two input samples and two mid-processing data
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const float32x2_t spl_in = vreinterpret_f32_u8 (
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vld1_u8 (reinterpret_cast <const uint8_t *> (in_ptr))
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);
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const float32x2_t spl_mid = vget_low_f32 (_filter [NBR_STAGES]._mem4);
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float32x4_t y = vcombine_f32 (spl_in, spl_mid);
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float32x4_t mem = _filter [0]._mem4;
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// Processes each stage
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StageProcNeon <NBR_STAGES>::process_sample_pos (&_filter [0], y, mem);
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_filter [NBR_STAGES]._mem4 = y;
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// Outputs the result
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const float out_0 = vgetq_lane_f32 (y, 3);
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const float out_1 = vgetq_lane_f32 (y, 2);
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low = (out_0 + out_1) * 0.5f;
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high = out_0 - low;
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}
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/*
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==============================================================================
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Name: process_block_split
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Description:
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Split (spectrum-wise) in half a block of samples. The lower part of the
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spectrum is a classic downsampling, equivalent to the output of
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process_block().
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The higher part is the complementary signal: original filter response
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is flipped from left to right, becoming a high-pass filter with the same
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cutoff frequency. This signal is then critically sampled (decimation by 2),
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flipping the spectrum: Fs/4...Fs/2 becomes Fs/4...0.
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Input and output blocks may overlap, see assert() for details.
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Input parameters:
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- in_ptr: Input array, containing nbr_spl * 2 samples.
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- nbr_spl: Number of samples for each output, > 0
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Output parameters:
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- out_l_ptr: Array for the output samples, lower part of the spectrum
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(downsampling). Capacity: nbr_spl samples.
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- out_h_ptr: Array for the output samples, higher part of the spectrum.
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Capacity: nbr_spl samples.
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Throws: Nothing
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==============================================================================
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*/
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template <int NC>
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void Downsampler2xNeon <NC>::process_block_split (float out_l_ptr [], float out_h_ptr [], const float in_ptr [], long nbr_spl)
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{
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assert (in_ptr != 0);
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assert (out_l_ptr != 0);
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assert (out_l_ptr <= in_ptr || out_l_ptr >= in_ptr + nbr_spl * 2);
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assert (out_h_ptr != 0);
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assert (out_h_ptr <= in_ptr || out_h_ptr >= in_ptr + nbr_spl * 2);
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assert (out_h_ptr != out_l_ptr);
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assert (nbr_spl > 0);
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long pos = 0;
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do
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{
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process_sample_split (out_l_ptr [pos], out_h_ptr [pos], in_ptr + pos * 2);
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++ pos;
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}
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while (pos < nbr_spl);
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}
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/*
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==============================================================================
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Name: clear_buffers
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Description:
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Clears filter memory, as if it processed silence since an infinite amount
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of time.
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Throws: Nothing
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==============================================================================
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*/
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template <int NC>
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void Downsampler2xNeon <NC>::clear_buffers ()
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{
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for (int i = 0; i < NBR_STAGES + 1; ++i)
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{
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_filter [i]._mem4 = vdupq_n_f32 (0);
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}
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}
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/*\\\ PROTECTED \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\*/
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/*\\\ PRIVATE \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\*/
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} // namespace hiir
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#endif // hiir_Downsampler2xNeon_CODEHEADER_INCLUDED
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/*\\\ EOF \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\*/
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