转载

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

JACK
PulseAudio
ALSA
CoreAudio
WASAPI
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
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; }

正文到此结束