1 /* 2 * Copyright (C) 2018 BlueKitchen GmbH 3 * 4 * Redistribution and use in source and binary forms, with or without 5 * modification, are permitted provided that the following conditions 6 * are met: 7 * 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 3. Neither the name of the copyright holders nor the names of 14 * contributors may be used to endorse or promote products derived 15 * from this software without specific prior written permission. 16 * 4. Any redistribution, use, or modification is done solely for 17 * personal benefit and not for any commercial purpose or for 18 * monetary gain. 19 * 20 * THIS SOFTWARE IS PROVIDED BY BLUEKITCHEN GMBH AND CONTRIBUTORS 21 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 22 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 23 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL MATTHIAS 24 * RINGWALD OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 25 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 26 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS 27 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 28 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 29 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF 30 * THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 * 33 * Please inquire about commercial licensing options at 34 * [email protected] 35 * 36 */ 37 38 #define BTSTACK_FILE__ "btstack_resample.c" 39 40 #include "btstack_resample.h" 41 42 void btstack_resample_init(btstack_resample_t * context, int num_channels){ 43 context->src_pos = 0; 44 context->src_step = 0x10000; // default resampling 1.0 45 context->last_sample[0] = 0; 46 context->last_sample[1] = 0; 47 context->num_channels = num_channels; 48 } 49 50 void btstack_resample_set_factor(btstack_resample_t * context, uint32_t src_step){ 51 context->src_step = src_step; 52 } 53 54 uint16_t btstack_resample_block(btstack_resample_t * context, const int16_t * input_buffer, uint32_t num_frames, int16_t * output_buffer){ 55 uint16_t dest_frames = 0; 56 uint16_t dest_samples = 0; 57 // samples between last sample of previous block and first sample in current block 58 while (context->src_pos >= 0xffff0000){ 59 const uint16_t t = context->src_pos & 0xffff; 60 int i; 61 for (i=0;i<context->num_channels;i++){ 62 int s1 = context->last_sample[i]; 63 int s2 = input_buffer[i]; 64 int os = ((s1*(0x10000 - t)) + (s2*t)) >> 16; 65 output_buffer[dest_samples++] = os; 66 } 67 dest_frames++; 68 context->src_pos += context->src_step; 69 } 70 // process current block 71 while (true){ 72 const uint16_t src_pos = context->src_pos >> 16; 73 const uint16_t t = context->src_pos & 0xffff; 74 int index = src_pos * context->num_channels; 75 int i; 76 if (src_pos >= (num_frames - 1)){ 77 // store last sample 78 for (i=0;i<context->num_channels;i++){ 79 context->last_sample[i] = input_buffer[index++]; 80 } 81 // samples processed 82 context->src_pos -= num_frames << 16; 83 break; 84 } 85 for (i=0;i<context->num_channels;i++){ 86 int s1 = input_buffer[index]; 87 int s2 = input_buffer[index+context->num_channels]; 88 int os = ((s1*(0x10000 - t)) + (s2*t)) >> 16; 89 output_buffer[dest_samples++] = os; 90 index++; 91 } 92 dest_frames++; 93 context->src_pos += context->src_step; 94 } 95 return dest_frames; 96 } 97