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Switches to using the supply-on-demand audio route through SDL.

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This gives an additional hook from which machine updates can be hooked, so separates that buffer size from any implicit frame rate assumptions.
This commit is contained in:
Thomas Harte 2017-11-22 19:36:39 -05:00
parent dc4f58e40c
commit c1b7bceec8
1 changed files with 32 additions and 6 deletions
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38
OSBindings/SDL/main.cpp
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@ -42,17 +42,41 @@ struct BestEffortUpdaterDelegate: public Concurrency::BestEffortUpdater::Delegat
}; };
// This is set to a relatively large number for now. // This is set to a relatively large number for now.
const int AudioBufferSize = 1024;
struct SpeakerDelegate: public Outputs::Speaker::Delegate { struct SpeakerDelegate: public Outputs::Speaker::Delegate {
static const int buffer_size = 1024;
void speaker_did_complete_samples(Outputs::Speaker *speaker, const std::vector<int16_t> &buffer) { void speaker_did_complete_samples(Outputs::Speaker *speaker, const std::vector<int16_t> &buffer) {
if(SDL_GetQueuedAudioSize(audio_device) < AudioBufferSize*3) std::lock_guard<std::mutex> lock_guard(audio_buffer_mutex_);
SDL_QueueAudio(audio_device, reinterpret_cast<const void *>(buffer.data()), static_cast<Uint32>(buffer.size() * sizeof(uint16_t))); if(audio_buffer_.size() > buffer_size) {
audio_buffer_.erase(audio_buffer_.begin(), audio_buffer_.end() - buffer_size);
}
audio_buffer_.insert(audio_buffer_.end(), buffer.begin(), buffer.end());
}
void audio_callback(Uint8 *stream, int len) {
updater->update(); updater->update();
std::lock_guard<std::mutex> lock_guard(audio_buffer_mutex_);
std::size_t sample_length = static_cast<std::size_t>(len) / sizeof(int16_t);
std::size_t copy_length = std::min(sample_length, audio_buffer_.size());
int16_t *target = static_cast<int16_t *>(static_cast<void *>(stream));
std::memcpy(stream, audio_buffer_.data(), copy_length * sizeof(int16_t));
if(copy_length < sample_length) {
std::memset(&target[copy_length], 0, (sample_length - copy_length) * sizeof(int16_t));
}
audio_buffer_.erase(audio_buffer_.begin(), audio_buffer_.begin() + copy_length);
}
static void SDL_audio_callback(void *userdata, Uint8 *stream, int len) {
reinterpret_cast<SpeakerDelegate *>(userdata)->audio_callback(stream, len);
} }
SDL_AudioDeviceID audio_device; SDL_AudioDeviceID audio_device;
Concurrency::BestEffortUpdater *updater; Concurrency::BestEffortUpdater *updater;
std::mutex audio_buffer_mutex_;
std::vector<int16_t> audio_buffer_;
}; };
bool KeyboardKeyForSDLScancode(SDL_Keycode scancode, Inputs::Keyboard::Key &key) { bool KeyboardKeyForSDLScancode(SDL_Keycode scancode, Inputs::Keyboard::Key &key) {
@ -345,11 +369,13 @@ int main(int argc, char *argv[]) {
desired_audio_spec.freq = 48000; // TODO: how can I get SDL to reveal the output rate of this machine? desired_audio_spec.freq = 48000; // TODO: how can I get SDL to reveal the output rate of this machine?
desired_audio_spec.format = AUDIO_S16; desired_audio_spec.format = AUDIO_S16;
desired_audio_spec.channels = 1; desired_audio_spec.channels = 1;
desired_audio_spec.samples = AudioBufferSize; desired_audio_spec.samples = SpeakerDelegate::buffer_size;
desired_audio_spec.callback = SpeakerDelegate::SDL_audio_callback;
desired_audio_spec.userdata = &speaker_delegate;
speaker_delegate.audio_device = SDL_OpenAudioDevice(nullptr, 0, &desired_audio_spec, &obtained_audio_spec, SDL_AUDIO_ALLOW_FREQUENCY_CHANGE); speaker_delegate.audio_device = SDL_OpenAudioDevice(nullptr, 0, &desired_audio_spec, &obtained_audio_spec, SDL_AUDIO_ALLOW_FREQUENCY_CHANGE);
speaker->set_output_rate(obtained_audio_spec.freq, obtained_audio_spec.samples); speaker->set_output_rate(obtained_audio_spec.freq, desired_audio_spec.samples);
speaker->set_delegate(&speaker_delegate); speaker->set_delegate(&speaker_delegate);
SDL_PauseAudioDevice(speaker_delegate.audio_device, 0); SDL_PauseAudioDevice(speaker_delegate.audio_device, 0);
} }