/*
* SPDX-License-Identifier: BSD-2-Clause
*
* Copyright (c) 2021 Goran Mekić
*
* 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.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 THE AUTHOR 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.
*/
#include <sys/soundcard.h>
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#ifndef SAMPLE_SIZE
#define SAMPLE_SIZE 16
#endif
/* Format can be unsigned, in which case replace S with U */
#if SAMPLE_SIZE == 32
typedef int32_t sample_t;
int format = AFMT_S32_NE; /* Signed 32bit native endian format */
#elif SAMPLE_SIZE == 16
typedef int16_t sample_t;
int format = AFMT_S16_NE; /* Signed 16bit native endian format */
#elif SAMPLE_SIZE == 8
typedef int8_t sample_t;
int format = AFMT_S8_NE; /* Signed 8bit native endian format */
#else
#error Unsupported sample format!
typedef int32_t sample_t;
int format = AFMT_S32_NE; /* Not a real value, just silencing
* compiler errors */
#endif
/*
* Minimal configuration for OSS
* For real world applications, this structure will probably contain many
* more fields
*/
typedef struct config {
char *device;
int channels;
int fd;
int format;
int frag;
int sample_count;
int sample_rate;
int sample_size;
int chsamples;
int mmap;
oss_audioinfo audio_info;
audio_buf_info buffer_info;
} config_t;
/*
* Error state is indicated by value=-1 in which case application exits
* with error
*/
static inline void
check_error(const int value, const char *message)
{
if (value == -1) {
fprintf(stderr, "OSS error: %s %s\n", message, strerror(errno));
exit(1);
}
}
/* Calculate frag by giving it minimal size of buffer */
static inline int
size2frag(int x)
{
int frag = 0;
while ((1 << frag) < x) {
++frag;
}
return frag;
}
/*
* Split input buffer into channels. Input buffer is in interleaved format
* which means if we have 2 channels (L and R), this is what the buffer of
* 8 samples would contain: L,R,L,R,L,R,L,R. The result are two channels
* containing: L,L,L,L and R,R,R,R.
*/
void
oss_split(config_t *config, sample_t *input, sample_t *output)
{
int channel;
int index;
for (int i = 0; i < config->sample_count; ++i) {
channel = i % config->channels;
index = i / config->channels;
output[channel * index] = input[i];
}
}
/*
* Convert channels into interleaved format and place it in output
* buffer
*/
void
oss_merge(config_t *config, sample_t *input, sample_t *output)
{
for (int channel = 0; channel < config->channels; ++channel) {
for (int index = 0; index < config->chsamples; ++index) {
output[index * config->channels + channel] = input[channel * index];
}
}
}
void
oss_init(config_t *config)
{
int error;
int tmp;
/* Open the device for read and write */
config->fd = open(config->device, O_RDWR);
check_error(config->fd, "open");
/* Get device information */
config->audio_info.dev = -1;
error = ioctl(config->fd, SNDCTL_ENGINEINFO, &(config->audio_info));
check_error(error, "SNDCTL_ENGINEINFO");
printf("min_channels: %d\n", config->audio_info.min_channels);
printf("max_channels: %d\n", config->audio_info.max_channels);
printf("latency: %d\n", config->audio_info.latency);
printf("handle: %s\n", config->audio_info.handle);
if (config->audio_info.min_rate > config->sample_rate || config->sample_rate > config->audio_info.max_rate) {
fprintf(stderr, "%s doesn't support chosen ", config->device);
fprintf(stderr, "samplerate of %dHz!\n", config->sample_rate);
exit(1);
}
if (config->channels < 1) {
config->channels = config->audio_info.max_channels;
}
/*
* If device is going to be used in mmap mode, disable all format
* conversions. Official OSS documentation states error code should not be
* checked. http://manuals.opensound.com/developer/mmap_test.c.html#LOC10
*/
if (config->mmap) {
tmp = 0;
ioctl(config->fd, SNDCTL_DSP_COOKEDMODE, &tmp);
}
/*
* Set number of channels. If number of channels is chosen to the value
* near the one wanted, save it in config
*/
tmp = config->channels;
error = ioctl(config->fd, SNDCTL_DSP_CHANNELS, &tmp);
check_error(error, "SNDCTL_DSP_CHANNELS");
if (tmp != config->channels) { /* or check if tmp is close enough? */
fprintf(stderr, "%s doesn't support chosen ", config->device);
fprintf(stderr, "channel count of %d", config->channels);
fprintf(stderr, ", set to %d!\n", tmp);
}
config->channels = tmp;
/* Set format, or bit size: 8, 16, 24 or 32 bit sample */
tmp = config->format;
error = ioctl(config->fd, SNDCTL_DSP_SETFMT, &tmp);
check_error(error, "SNDCTL_DSP_SETFMT");
if (tmp != config->format) {
fprintf(stderr, "%s doesn't support chosen sample format!\n", config->device);
exit(1);
}
/* Most common values for samplerate (in kHz): 44.1, 48, 88.2, 96 */
tmp = config->sample_rate;
error = ioctl(config->fd, SNDCTL_DSP_SPEED, &tmp);
check_error(error, "SNDCTL_DSP_SPEED");
/* Get and check device capabilities */
error = ioctl(config->fd, SNDCTL_DSP_GETCAPS, &(config->audio_info.caps));
check_error(error, "SNDCTL_DSP_GETCAPS");
if (!(config->audio_info.caps & PCM_CAP_DUPLEX)) {
fprintf(stderr, "Device doesn't support full duplex!\n");
exit(1);
}
if (config->mmap) {
if (!(config->audio_info.caps & PCM_CAP_TRIGGER)) {
fprintf(stderr, "Device doesn't support triggering!\n");
exit(1);
}
if (!(config->audio_info.caps & PCM_CAP_MMAP)) {
fprintf(stderr, "Device doesn't support mmap mode!\n");
exit(1);
}
}
/*
* If desired frag is smaller than minimum, based on number of channels
* and format (size in bits: 8, 16, 24, 32), set that as frag. Buffer size
* is 2^frag, but the real size of the buffer will be read when the
* configuration of the device is successfull
*/
int min_frag = size2frag(config->sample_size * config->channels);
if (config->frag < min_frag) {
config->frag = min_frag;
}
/*
* Allocate buffer in fragments. Total buffer will be split in number
* of fragments (2 by default)
*/
if (config->buffer_info.fragments < 0) {
config->buffer_info.fragments = 2;
}
tmp = ((config->buffer_info.fragments) << 16) | config->frag;
error = ioctl(config->fd, SNDCTL_DSP_SETFRAGMENT, &tmp);
check_error(error, "SNDCTL_DSP_SETFRAGMENT");
/* When all is set and ready to go, get the size of buffer */
error = ioctl(config->fd, SNDCTL_DSP_GETOSPACE, &(config->buffer_info));
check_error(error, "SNDCTL_DSP_GETOSPACE");
if (config->buffer_info.bytes < 1) {
fprintf(
stderr,
"OSS buffer error: buffer size can not be %d\n",
config->buffer_info.bytes
);
exit(1);
}
config->sample_count = config->buffer_info.bytes / config->sample_size;
config->chsamples = config->sample_count / config->channels;
}
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