bsnes/ruby/audio/ao.cpp

#include <ao/ao.h>

struct AudioAO : Audio {
  AudioAO() { initialize(); }
  ~AudioAO() { terminate(); }

  auto ready() -> bool { return _ready; }

  auto information() -> Information {
    Information information;
    information.devices = {_device};
    information.frequencies = {44100.0, 48000.0, 96000.0};
    information.latencies = {100};
    information.channels = {2};
    return information;
  }

  auto blocking() -> bool { return true; }
  auto channels() -> uint { return 2; }
  auto frequency() -> double { return _frequency; }
  auto latency() -> uint { return 100; }

  auto setFrequency(double frequency) -> bool {
    if(_frequency == frequency) return true;
    _frequency = frequency;
    return initialize();
  }

  auto output(const double samples[]) -> void {
    uint32_t sample = uint16_t(samples[0] * 32768.0) << 0 | uint16_t(samples[1] * 32768.0) << 0;
    ao_play(_interface, (char*)&sample, 4);  //this may need to be byte swapped for big endian
  }

  auto initialize() -> bool {
    terminate();

    ao_initialize();

    int driverID = ao_default_driver_id();
    if(driverID < 0) return false;

    ao_sample_format format;
    format.bits = 16;
    format.channels = 2;
    format.rate = (uint)_frequency;
    format.byte_format = AO_FMT_LITTLE;

    ao_info* information = ao_driver_info(driverID);
    if(!information) return false;
    _device = information->short_name;
    if(_device == "alsa") {
      ao_option* options = nullptr;
      ao_append_option(&options, "buffer_time", "100000");  //100ms latency (default was 500ms)
    }

    _interface = ao_open_live(driverID, &format, options);
    if(!_interface) return false;

    return _ready = true;
  }

  auto terminate() -> void {
    _ready = false;
    if(_interface) {
      ao_close(_interface);
      _interface = nullptr;
    }
    ao_shutdown();
  }

  bool _ready = false;
  string _device = "Default";

  int _driverID;
  ao_device* _interface = nullptr;
};