libsoundio跨平台实时音频驱动
libsoundio 是轻量级抽象的声音驱动程序，是一个跨平台实时音频输入和输出的 C99 库。libsoundio 提供文档完善的 API，适用于实时软件，比如游戏，数字音频工作站，音乐播放器等等实用工具。
libsoundio 非常健壮，可以正确处理内存不足的状态。
特性&限制
支持的后端
Dummy (silence)
支持原始设备和共享设备
支持设备 ID 和友好的名字
支持优化每个后端的使用
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C 语言库，仅仅依赖于后端 API 库和 libc
支持频道布局
基础正弦波示例
#include <soundio/soundio.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
static const float PI = 3.1415926535f;
static float seconds_offset = 0.0f;
static void write_callback(struct SoundIoOutStream *outstream,
int frame_count_min, int frame_count_max)
{
const struct SoundIoChannelLayout *layout = &outstream->layout;
float float_sample_rate = outstream->sample_rate;
float seconds_per_frame = 1.0f / float_sample_rate;
struct SoundIoChannelArea *areas;
int frames_left = frame_count_max;
int err;
while (frames_left > 0) {
int frame_count = frames_left;
if ((err = soundio_outstream_begin_write(outstream, &areas, &frame_count))) {
fprintf(stderr, "%s\n", soundio_strerror(err));
exit(1);
}
if (!frame_count)
break;
float pitch = 440.0f;
float radians_per_second = pitch * 2.0f * PI;
for (int frame = 0; frame < frame_count; frame += 1) {
float sample = sinf((seconds_offset + frame * seconds_per_frame) * radians_per_second);
for (int channel = 0; channel < layout->channel_count; channel += 1) {
float *ptr = (float*)(areas[channel].ptr + areas[channel].step * frame);
*ptr = sample;
}
}
seconds_offset += seconds_per_frame * frame_count;
if ((err = soundio_outstream_end_write(outstream))) {
fprintf(stderr, "%s\n", soundio_strerror(err));
exit(1);
}
frames_left -= frame_count;
}
}
int main(int argc, char **argv) {
int err;
struct SoundIo *soundio = soundio_create();
if (!soundio) {
fprintf(stderr, "out of memory\n");
return 1;
}
if ((err = soundio_connect(soundio))) {
fprintf(stderr, "error connecting: %s", soundio_strerror(err));
return 1;
}
soundio_flush_events(soundio);
int default_out_device_index = soundio_default_output_device_index(soundio);
if (default_out_device_index < 0) {
fprintf(stderr, "no output device found");
return 1;
}
struct SoundIoDevice *device = soundio_get_output_device(soundio, default_out_device_index);
if (!device) {
fprintf(stderr, "out of memory");
return 1;
}
fprintf(stderr, "Output device: %s\n", device->name);
struct SoundIoOutStream *outstream = soundio_outstream_create(device);
outstream->format = SoundIoFormatFloat32NE;
outstream->write_callback = write_callback;
if ((err = soundio_outstream_open(outstream))) {
fprintf(stderr, "unable to open device: %s", soundio_strerror(err));
return 1;
}
if (outstream->layout_error)
fprintf(stderr, "unable to set channel layout: %s\n", soundio_strerror(outstream->layout_error));
if ((err = soundio_outstream_start(outstream))) {
fprintf(stderr, "unable to start device: %s", soundio_strerror(err));
return 1;
}
for (;;)
soundio_wait_events(soundio);
soundio_outstream_destroy(outstream);
soundio_device_unref(device);
soundio_destroy(soundio);
return 0;
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