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 <sys/soundcard.h>
33 #include "oss.h"
34
35 /*
36 * Split input buffer into channels. The input buffer is in interleaved format,
37 * which means if we have 2 channels (L and R), this is what the buffer of 8
38 * samples would contain: L,R,L,R,L,R,L,R. The result of this function is a
39 * buffer containing: L,L,L,L,R,R,R,R.
40 */
41 static void
to_channels(struct config * config,void * output)42 to_channels(struct config *config, void *output)
43 {
44 uint8_t *in = config->buf;
45 uint8_t *out = output;
46 int i, channel, index, offset, byte;
47
48 /* Iterate over bytes in the input buffer */
49 for (byte = 0; byte < config->buffer_info.bytes;
50 byte += config->sample_size) {
51 /*
52 * Get index of a sample in the input buffer measured in
53 * samples
54 */
55 i = byte / config->sample_size;
56
57 /* Get which channel is being processed */
58 channel = i % config->audio_info.max_channels;
59
60 /* Get offset of the sample inside a single channel */
61 offset = i / config->audio_info.max_channels;
62
63 /* Get index of a sample in the output buffer */
64 index = (channel * config->chsamples + offset) *
65 config->sample_size;
66
67 /* Copy singe sample from input to output */
68 memcpy(out+index, in+byte, config->sample_size);
69 }
70 }
71
72 /*
73 * Convert channels into interleaved format and put into output buffer
74 */
75 static void
to_interleaved(struct config * config,void * input)76 to_interleaved(struct config *config, void *input)
77 {
78 uint8_t *out = config->buf;
79 uint8_t *in = input;
80 int i, index, offset, channel, byte;
81
82 /* Iterate over bytes in the input buffer */
83 for (byte = 0; byte < config->buffer_info.bytes;
84 byte += config->sample_size) {
85 /*
86 * Get index of a sample in the input buffer measured in
87 * samples
88 */
89 index = byte / config->sample_size;
90
91 /* Get which channel is being processed */
92 channel = index / config->chsamples;
93
94 /* Get offset of the sample inside a single channel */
95 offset = index % config->chsamples;
96
97 /* Get index of a sample in the output buffer */
98 i = (config->audio_info.max_channels * offset + channel) *
99 config->sample_size;
100
101 /* Copy singe sample from input to output */
102 memcpy(out+i, in+byte, config->sample_size);
103 }
104 }
105
106 int
main(int argc,char * argv[])107 main(int argc, char *argv[])
108 {
109 struct config config = {
110 .device = "/dev/dsp",
111 .mode = O_RDWR,
112 .format = AFMT_S32_NE,
113 .sample_rate = 48000,
114 };
115 int32_t *channels;
116 int rc, bytes;
117
118 oss_init(&config);
119 if (config.format != AFMT_S32_NE)
120 errx(1, "Device doesn't support signed 32bit samples. "
121 "Check with 'sndctl' if it can be configured for 's32le' format.");
122 bytes = config.buffer_info.bytes;
123 channels = malloc(bytes);
124
125 for (;;) {
126 if ((rc = read(config.fd, config.buf, bytes)) < bytes) {
127 warn("Requested %d bytes, but read %d!\n", bytes, rc);
128 break;
129 }
130 /*
131 * Strictly speaking, we could omit "channels" and operate only
132 * using config->buf, but this example tries to show the real
133 * world application usage. The problem is that the buffer is
134 * in interleaved format, and if you'd like to do any
135 * processing and/or mixing, it is easier to do that if samples
136 * are grouped per channel.
137 */
138 to_channels(&config, channels);
139 to_interleaved(&config, channels);
140 if ((rc = write(config.fd, config.buf, bytes)) < bytes) {
141 warn("Requested %d bytes, but wrote %d!\n", bytes, rc);
142 break;
143 }
144 }
145
146 free(channels);
147 free(config.buf);
148 close(config.fd);
149
150 return (0);
151 }
152