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 2019-02-21 11:27:19 +01:00
parent ce00c6755a
commit c21cc0eb6e
2 changed files with 183 additions and 0 deletions

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

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