framestream2 (with rigtorp/SPSCQueue)

src/content/sdl_video_frame_stream2.cpp

@@ -0,0 +1,81 @@
+#include "./sdl_video_frame_stream2.hpp"
+
+#include <chrono>
+#include <cstdint>
+#include <iostream>
+#include <memory>
+#include <thread>
+
+SDLVideoCameraContent::SDLVideoCameraContent(void) {
+	int devcount = 0;
+	SDL_CameraDeviceID *devices = SDL_GetCameraDevices(&devcount);
+
+	if (devices == nullptr || devcount < 1) {
+		throw int(1); // TODO: proper exception?
+	}
+
+	std::cout << "### found cameras:\n";
+	for (int i = 0; i < devcount; i++) {
+		const SDL_CameraDeviceID device = devices[i];
+		char *name = SDL_GetCameraDeviceName(device);
+
+		std::cout << "  - Camera #" << i << ": " << name << "\n";
+
+		SDL_free(name);
+	}
+
+	_camera = {
+		SDL_OpenCameraDevice(devices[0], nullptr),
+		&SDL_CloseCamera
+	};
+	if (!static_cast<bool>(_camera)) {
+		throw int(2);
+	}
+
+	SDL_CameraSpec spec;
+	float interval {0.1f};
+	if (SDL_GetCameraFormat(_camera.get(), &spec) < 0) {
+		// meh
+	} else {
+		// interval
+		interval = float(spec.interval_numerator)/float(spec.interval_denominator);
+		std::cout << "camera interval: " << interval*1000 << "ms\n";
+	}
+
+	_thread = std::thread([this, interval](void) {
+		while (!_thread_should_quit) {
+			Uint64 timestampNS = 0;
+			SDL_Surface* sdl_frame_next = SDL_AcquireCameraFrame(_camera.get(), &timestampNS);
+
+			// no new frame yet, or error
+			if (sdl_frame_next == nullptr) {
+				// only sleep 1/10, we expected a frame
+				std::this_thread::sleep_for(std::chrono::milliseconds(int64_t(interval*1000 / 10)));
+				continue;
+			}
+
+			SDLVideoFrame new_frame {
+				timestampNS,
+				sdl_frame_next
+			};
+
+			bool someone_listening = pushValue(new_frame);
+
+			SDL_ReleaseCameraFrame(_camera.get(), sdl_frame_next);
+
+			if (someone_listening) {
+				// TODO: maybe double the freq?
+				std::this_thread::sleep_for(std::chrono::milliseconds(int64_t(interval*1000)));
+			} else {
+				// we just sleep 4x as long, bc no one is listening
+				std::this_thread::sleep_for(std::chrono::milliseconds(int64_t(interval*1000*4)));
+			}
+		}
+	});
+}
+
+SDLVideoCameraContent::~SDLVideoCameraContent(void) {
+	_thread_should_quit = true;
+	_thread.join();
+	// TODO: what to do if readers are still present?
+}