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#include <alsa/asoundlib.h>
struct AudioALSA : AudioDriver {
AudioALSA& self = *this;
AudioALSA(Audio& super) : AudioDriver(super) {}
~AudioALSA() { terminate(); }
auto create() -> bool override {
super.setDevice("default");
super.setChannels(2);
super.setFrequency(48000);
super.setLatency(20);
return initialize();
}
auto driver() -> string override { return "ALSA"; }
auto ready() -> bool override { return _ready; }
auto hasBlocking() -> bool override { return true; }
auto hasDynamic() -> bool override { return true; }
auto hasDevices() -> vector<string> override {
vector<string> devices;
char** list;
if(snd_device_name_hint(-1, "pcm", (void***)&list) == 0) {
u32 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;
}
auto hasChannels() -> vector<u32> override {
return {2};
}
auto hasFrequencies() -> vector<u32> override {
return {44100, 48000, 96000};
}
auto hasLatencies() -> vector<u32> override {
return {20, 40, 60, 80, 100};
}
auto setDevice(string device) -> bool override { return initialize(); }
auto setBlocking(bool blocking) -> bool override { return true; }
auto setChannels(u32 channels) -> bool override { return true; }
auto setFrequency(u32 frequency) -> bool override { return initialize(); }
auto setLatency(u32 latency) -> bool override { return initialize(); }
auto level() -> f64 override {
snd_pcm_sframes_t available;
for(u32 timeout : range(256)) {
available = snd_pcm_avail_update(_interface);
if(available >= 0) break;
snd_pcm_recover(_interface, available, 1);
}
return (f64)(_bufferSize - available) / _bufferSize;
}
auto output(const f64 samples[]) -> void override {
_buffer[_offset] = (u16)sclamp<16>(samples[0] * 32767.0) << 0;
_buffer[_offset] |= (u16)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);
continue;
}
if(available < _offset) {
if(!self.blocking) {
_offset = 0;
return;
}
s32 error = snd_pcm_wait(_interface, -1);
if(error < 0) snd_pcm_recover(_interface, error, 1);
}
} while(available < _offset);
u32* output = _buffer;
s32 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<u32>(_buffer, output, _offset);
}
}
private:
auto initialize() -> bool {
terminate();
if(!hasDevices().find(self.device)) self.device = "default";
if(snd_pcm_open(&_interface, self.device, SND_PCM_STREAM_PLAYBACK, SND_PCM_NONBLOCK) < 0) return terminate(), false;
u32 rate = self.frequency;
u32 bufferTime = self.latency * 1000;
u32 periodTime = self.latency * 1000 / 8;
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 / 2) < 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;
}
}
bool _ready = false;
snd_pcm_t* _interface = nullptr;
snd_pcm_uframes_t _bufferSize;
snd_pcm_uframes_t _periodSize;
u32* _buffer = nullptr;
u32 _offset = 0;
};
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