1 /* 2 * SPDX-License-Identifier: BSD-2-Clause 3 * 4 * Copyright (c) 2024 The FreeBSD Foundation 5 * Copyright (c) 2025 Goran Mekić 6 * 7 * Portions of this software were developed by Christos Margiolis 8 * <christos@FreeBSD.org> under sponsorship from the FreeBSD Foundation. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29 * SUCH DAMAGE. 30 */ 31 32 #include "oss.h" 33 34 /* 35 * Split input buffer into channels. The input buffer is in interleaved format, 36 * which means if we have 2 channels (L and R), this is what the buffer of 8 37 * samples would contain: L,R,L,R,L,R,L,R. The result of this function is a 38 * buffer containing: L,L,L,L,R,R,R,R. 39 */ 40 static void 41 to_channels(struct config *config, void *output) 42 { 43 uint8_t *in = config->buf; 44 uint8_t *out = output; 45 int i, channel, index, offset, byte; 46 47 /* Iterate over bytes in the input buffer */ 48 for (byte = 0; byte < config->buffer_info.bytes; 49 byte += config->sample_size) { 50 /* 51 * Get index of a sample in the input buffer measured in 52 * samples 53 */ 54 i = byte / config->sample_size; 55 56 /* Get which channel is being processed */ 57 channel = i % config->audio_info.max_channels; 58 59 /* Get offset of the sample inside a single channel */ 60 offset = i / config->audio_info.max_channels; 61 62 /* Get index of a sample in the output buffer */ 63 index = (channel * config->chsamples + offset) * 64 config->sample_size; 65 66 /* Copy singe sample from input to output */ 67 memcpy(out+index, in+byte, config->sample_size); 68 } 69 } 70 71 /* 72 * Convert channels into interleaved format and put into output buffer 73 */ 74 static void 75 to_interleaved(struct config *config, void *input) 76 { 77 uint8_t *out = config->buf; 78 uint8_t *in = input; 79 int i, index, offset, channel, byte; 80 81 /* Iterate over bytes in the input buffer */ 82 for (byte = 0; byte < config->buffer_info.bytes; 83 byte += config->sample_size) { 84 /* 85 * Get index of a sample in the input buffer measured in 86 * samples 87 */ 88 index = byte / config->sample_size; 89 90 /* Get which channel is being processed */ 91 channel = index / config->chsamples; 92 93 /* Get offset of the sample inside a single channel */ 94 offset = index % config->chsamples; 95 96 /* Get index of a sample in the output buffer */ 97 i = (config->audio_info.max_channels * offset + channel) * 98 config->sample_size; 99 100 /* Copy singe sample from input to output */ 101 memcpy(out+i, in+byte, config->sample_size); 102 } 103 } 104 105 int 106 main(int argc, char *argv[]) 107 { 108 struct config config = { 109 .device = "/dev/dsp", 110 .mode = O_RDWR, 111 .format = AFMT_S32_NE, 112 .sample_rate = 48000, 113 }; 114 int32_t *channels; 115 int rc, bytes; 116 117 oss_init(&config); 118 bytes = config.buffer_info.bytes; 119 channels = malloc(bytes); 120 121 for (;;) { 122 if ((rc = read(config.fd, config.buf, bytes)) < bytes) { 123 warn("Requested %d bytes, but read %d!\n", bytes, rc); 124 break; 125 } 126 /* 127 * Strictly speaking, we could omit "channels" and operate only 128 * using config->buf, but this example tries to show the real 129 * world application usage. The problem is that the buffer is 130 * in interleaved format, and if you'd like to do any 131 * processing and/or mixing, it is easier to do that if samples 132 * are grouped per channel. 133 */ 134 to_channels(&config, channels); 135 to_interleaved(&config, channels); 136 if ((rc = write(config.fd, config.buf, bytes)) < bytes) { 137 warn("Requested %d bytes, but wrote %d!\n", bytes, rc); 138 break; 139 } 140 } 141 142 free(channels); 143 free(config.buf); 144 close(config.fd); 145 146 return (0); 147 } 148