mirror of
https://github.com/bluekitchen/btstack.git
synced 2025-03-18 13:20:46 +00:00
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
parent
ce00c6755a
commit
c21cc0eb6e
94
src/btstack_resample.c
Normal file
94
src/btstack_resample.c
Normal file
@ -0,0 +1,94 @@
|
||||
/*
|
||||
* 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;
|
||||
}
|
||||
89
src/btstack_resample.h
Normal file
89
src/btstack_resample.h
Normal file
@ -0,0 +1,89 @@
|
||||
/*
|
||||
* 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
|
||||
Loading…
x
Reference in New Issue
Block a user