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#include <alsa/asoundlib.h>
struct AudioALSA : Audio {
AudioALSA() { initialize(); }
~AudioALSA() { terminate(); }
auto availableDevices() -> string_vector {
return queryDevices();
}
auto availableFrequencies() -> vector<double> {
return {44100.0, 48000.0, 96000.0};
}
auto availableLatencies() -> vector<uint> {
return {20, 40, 60, 80, 100};
}
auto availableChannels() -> vector<uint> {
return {2};
}
auto ready() -> bool { return _ready; }
auto device() -> string { return _device; }
auto blocking() -> bool { return _blocking; }
auto channels() -> uint { return 2; }
auto frequency() -> double { return _frequency; }
auto latency() -> uint { return _latency; }
auto setDevice(string device) -> bool {
if(_device == device) return true;
_device = device;
return initialize();
}
auto setBlocking(bool blocking) -> bool {
if(_blocking == blocking) return true;
_blocking = blocking;
return true;
}
auto setFrequency(double frequency) -> bool {
if(_frequency == frequency) return true;
_frequency = frequency;
return initialize();
}
auto setLatency(uint latency) -> bool {
if(_latency == latency) return true;
_latency = latency;
return initialize();
}
auto output(const double samples[]) -> void {
if(!ready()) return;
_buffer[_offset] = (uint16_t)sclamp<16>(samples[0] * 32767.0) << 0;
_buffer[_offset] |= (uint16_t)sclamp<16>(samples[1] * 32767.0) << 16;
if(++_offset < _periodSize) return;
snd_pcm_sframes_t available;
do {
available = snd_pcm_avail_update(_interface);
if(available < 0) snd_pcm_recover(_interface, available, 1);
if(available < _offset) {
if(!_blocking) {
_offset = 0;
return;
}
int error = snd_pcm_wait(_interface, -1);
if(error < 0) snd_pcm_recover(_interface, error, 1);
}
} while(available < _offset);
uint32_t* output = _buffer;
int i = 4;
while(_offset > 0 && i--) {
snd_pcm_sframes_t written = snd_pcm_writei(_interface, output, _offset);
if(written < 0) {
//no samples written
snd_pcm_recover(_interface, written, 1);
} else if(written <= _offset) {
_offset -= written;
output += written;
}
}
if(i < 0) {
if(_buffer == output) {
_offset--;
output++;
}
memory::move(_buffer, output, _offset * sizeof(uint32_t));
}
}
private:
auto initialize() -> bool {
terminate();
string device = "default";
if(queryDevices().find(_device)) device = _device;
if(snd_pcm_open(&_interface, device, SND_PCM_STREAM_PLAYBACK, SND_PCM_NONBLOCK) < 0) return terminate(), false;
uint rate = (uint)_frequency;
uint bufferTime = _latency * 1000;
uint periodTime = _latency * 1000 / 4;
snd_pcm_hw_params_t* hardwareParameters;
snd_pcm_hw_params_alloca(&hardwareParameters);
if(snd_pcm_hw_params_any(_interface, hardwareParameters) < 0) return terminate(), false;
if(snd_pcm_hw_params_set_access(_interface, hardwareParameters, SND_PCM_ACCESS_RW_INTERLEAVED) < 0
|| snd_pcm_hw_params_set_format(_interface, hardwareParameters, SND_PCM_FORMAT_S16_LE) < 0
|| snd_pcm_hw_params_set_channels(_interface, hardwareParameters, 2) < 0
|| snd_pcm_hw_params_set_rate_near(_interface, hardwareParameters, &rate, 0) < 0
|| snd_pcm_hw_params_set_period_time_near(_interface, hardwareParameters, &periodTime, 0) < 0
|| snd_pcm_hw_params_set_buffer_time_near(_interface, hardwareParameters, &bufferTime, 0) < 0
) return terminate(), false;
if(snd_pcm_hw_params(_interface, hardwareParameters) < 0) return terminate(), false;
if(snd_pcm_get_params(_interface, &_bufferSize, &_periodSize) < 0) return terminate(), false;
snd_pcm_sw_params_t* softwareParameters;
snd_pcm_sw_params_alloca(&softwareParameters);
if(snd_pcm_sw_params_current(_interface, softwareParameters) < 0) return terminate(), false;
if(snd_pcm_sw_params_set_start_threshold(_interface, softwareParameters,
(_bufferSize / _periodSize) * _periodSize) < 0
) return terminate(), false;
if(snd_pcm_sw_params(_interface, softwareParameters) < 0) return terminate(), false;
_buffer = new uint32_t[_periodSize]();
_offset = 0;
return _ready = true;
}
auto terminate() -> void {
_ready = false;
if(_interface) {
//snd_pcm_drain(_interface); //prevents popping noise; but causes multi-second lag
snd_pcm_close(_interface);
_interface = nullptr;
}
if(_buffer) {
delete[] _buffer;
_buffer = nullptr;
}
}
auto queryDevices() -> string_vector {
string_vector devices;
char** list;
if(snd_device_name_hint(-1, "pcm", (void***)&list) == 0) {
uint index = 0;
while(list[index]) {
char* deviceName = snd_device_name_get_hint(list[index], "NAME");
if(deviceName) devices.append(deviceName);
free(deviceName);
index++;
}
}
snd_device_name_free_hint((void**)list);
return devices;
}
bool _ready = false;
string _device;
bool _blocking = true;
double _frequency = 48000.0;
uint _latency = 40;
snd_pcm_t* _interface = nullptr;
snd_pcm_uframes_t _bufferSize;
snd_pcm_uframes_t _periodSize;
uint32_t* _buffer = nullptr;
uint _offset = 0;
};
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