frame refactoring, add audio frame and sdl default device input

src/content/sdl_audio_frame_stream2.cpp

@@ -0,0 +1,79 @@
+#include "./sdl_audio_frame_stream2.hpp"
+#include "SDL_audio.h"
+
+#include <iostream>
+#include <vector>
+
+SDLAudioInputDevice::SDLAudioInputDevice(void) : _stream{nullptr, &SDL_DestroyAudioStream} {
+	constexpr SDL_AudioSpec spec = { SDL_AUDIO_S16, 1, 48000 };
+
+	_stream = {
+		SDL_OpenAudioDeviceStream(SDL_AUDIO_DEVICE_DEFAULT_CAPTURE, &spec, nullptr, nullptr),
+		&SDL_DestroyAudioStream
+	};
+
+	if (!static_cast<bool>(_stream)) {
+		std::cerr << "SDL open audio device failed!\n";
+	}
+
+	const auto audio_device_id = SDL_GetAudioStreamDevice(_stream.get());
+	SDL_ResumeAudioDevice(audio_device_id);
+
+	static constexpr size_t buffer_size {512}; // in samples
+	const auto interval_ms {buffer_size/(spec.freq * 1000)};
+
+	_thread = std::thread([this, interval_ms, spec](void) {
+		while (!_thread_should_quit) {
+			//static std::vector<int16_t> buffer(buffer_size);
+			static AudioFrame tmp_frame {
+				0, // TODO: seq
+				spec.freq, spec.channels,
+				std::vector<int16_t>(buffer_size)
+			};
+
+			auto& buffer = std::get<std::vector<int16_t>>(tmp_frame.buffer);
+			buffer.resize(buffer_size);
+
+			const auto read_bytes = SDL_GetAudioStreamData(
+				_stream.get(),
+				buffer.data(),
+				buffer.size()*sizeof(int16_t)
+			);
+			//if (read_bytes != 0) {
+				//std::cerr << "read " << read_bytes << "/" << buffer.size()*sizeof(int16_t) << " audio bytes\n";
+			//}
+
+			// no new frame yet, or error
+			if (read_bytes <= 0) {
+				// only sleep 1/5, we expected a frame
+				std::this_thread::sleep_for(std::chrono::milliseconds(int64_t(interval_ms/5)));
+				continue;
+			}
+
+			buffer.resize(read_bytes/sizeof(int16_t)); // this might be costly?
+
+			bool someone_listening {false};
+			someone_listening = push(tmp_frame);
+
+			if (someone_listening) {
+				// double the interval on acquire
+				std::this_thread::sleep_for(std::chrono::milliseconds(int64_t(interval_ms/2)));
+			} else {
+				std::cerr << "i guess no one is listening\n";
+				// we just sleep 32x as long, bc no one is listening
+				// with the hardcoded settings, this is ~320ms
+				// TODO: just hardcode something like 500ms?
+				// TODO: suspend
+				std::this_thread::sleep_for(std::chrono::milliseconds(int64_t(interval_ms*32)));
+			}
+		}
+	});
+}
+
+SDLAudioInputDevice::~SDLAudioInputDevice(void) {
+	// TODO: pause audio device?
+	_thread_should_quit = true;
+	_thread.join();
+	// TODO: what to do if readers are still present?
+}
+