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btstack_resample: add inear resampling for 16-bit audio code samples using 16 bit/16 bit fixed point math
This commit is contained in:
Matthias Ringwald
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ce00c6755a
commit
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94
src/btstack_resample.c
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94
src/btstack_resample.c
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/*
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* Copyright (C) 2018 BlueKitchen GmbH
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the copyright holders nor the names of
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* contributors may be used to endorse or promote products derived
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* from this software without specific prior written permission.
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* 4. Any redistribution, use, or modification is done solely for
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* personal benefit and not for any commercial purpose or for
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* monetary gain.
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*
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* THIS SOFTWARE IS PROVIDED BY BLUEKITCHEN GMBH AND CONTRIBUTORS
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* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL MATTHIAS
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* RINGWALD OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
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* THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* Please inquire about commercial licensing options at
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* contact@bluekitchen-gmbh.com
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*
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*/
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#include "btstack_resample.h"
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void btstack_resample_init(btstack_resample_t * context, int num_channels){
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context->src_pos = 0;
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context->src_step = 0x10000; // default resampling 1.0
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context->last_sample[0] = 0;
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context->last_sample[1] = 0;
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context->num_channels = num_channels;
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}
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void btstack_resample_set_factor(btstack_resample_t * context, uint32_t src_step){
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context->src_step = src_step;
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}
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uint16_t btstack_resample_block(btstack_resample_t * context, const int16_t * input_buffer, uint32_t num_frames, int16_t * output_buffer){
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uint16_t dest_frames = 0;
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uint16_t dest_samples = 0;
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// samples between last sample of previous block and first sample in current block
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while (context->src_pos >= 0xffff0000){
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const uint16_t t = context->src_pos & 0xffff;
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int i;
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for (i=0;i<context->num_channels;i++){
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int s1 = context->last_sample[i];
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int s2 = input_buffer[i];
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int os = (s1*(0x10000 - t) + s2*t) >> 16;
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output_buffer[dest_samples++] = os;
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}
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dest_frames++;
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context->src_pos += context->src_step;
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}
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// process current block
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while (1){
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const uint16_t src_pos = context->src_pos >> 16;
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const uint16_t t = context->src_pos & 0xffff;
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int index = src_pos * context->num_channels;
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int i;
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if (src_pos >= (num_frames - 1)){
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// store last sample
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for (i=0;i<context->num_channels;i++){
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context->last_sample[i] = input_buffer[index++];
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}
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// samples processed
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context->src_pos -= num_frames << 16;
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break;
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}
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for (i=0;i<context->num_channels;i++){
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int s1 = input_buffer[index];
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int s2 = input_buffer[index+context->num_channels];
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int os = (s1*(0x10000 - t) + s2*t) >> 16;
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output_buffer[dest_samples++] = os;
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index++;
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}
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dest_frames++;
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context->src_pos += context->src_step;
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}
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return dest_frames;
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}
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89
src/btstack_resample.h
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89
src/btstack_resample.h
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@ -0,0 +1,89 @@
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/*
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* Copyright (C) 2018 BlueKitchen GmbH
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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||||
* notice, this list of conditions and the following disclaimer in the
|
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the copyright holders nor the names of
|
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* contributors may be used to endorse or promote products derived
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* from this software without specific prior written permission.
|
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* 4. Any redistribution, use, or modification is done solely for
|
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* personal benefit and not for any commercial purpose or for
|
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* monetary gain.
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*
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* THIS SOFTWARE IS PROVIDED BY BLUEKITCHEN GMBH AND CONTRIBUTORS
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* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
|
||||
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
|
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL MATTHIAS
|
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* RINGWALD OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
|
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
|
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
|
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
|
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* THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* Please inquire about commercial licensing options at
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* contact@bluekitchen-gmbh.com
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*
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*/
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#ifndef __BTSTACK_RESAMPLE_H
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#define __BTSTACK_RESAMPLE_H
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#include <stdint.h>
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#if defined __cplusplus
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extern "C" {
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#endif
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/*
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* btstack_resample.h
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*
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* Linear resampling for 16-bit audio code samples using 16 bit/16 bit fixed point math
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*/
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#define BTSTACK_RESAMPLE_MAX_CHANNELS 2
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typedef struct {
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uint32_t src_pos;
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uint32_t src_step;
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int16_t last_sample[BTSTACK_RESAMPLE_MAX_CHANNELS];
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int num_channels;
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} btstack_resample_t;
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/**
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* @brief Init resample context
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* @param num_channels
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* @returns btstack_audio implementation
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*/
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void btstack_resample_init(btstack_resample_t * context, int num_channels);
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/**
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* @brief Set resampling factor
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* @param factor as fixed point value, identity is 0x10000
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*/
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void btstack_resample_set_factor(btstack_resample_t * context, uint32_t factor);
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/**
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* @brief Process block of input samples
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* @note size of output buffer is not checked
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* @param input_buffer
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* @param num_frames
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* @param output_buffer
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* @returns number destination frames
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*/
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uint16_t btstack_resample_block(btstack_resample_t * context, const int16_t * input_buffer, uint32_t num_frames, int16_t * output_buffer);
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#if defined __cplusplus
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}
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#endif
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#endif
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