/* * 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 #include #include #include #include #include #include #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; }