media_helpers.cpp

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#include "media_helpers.hpp"
 
#include <mxvk/mxvk_cv.hpp>
 
#include <chrono>
#include <exception>
#include <iostream>
#include <utility>
 
namespace acmxvk {
    LatestCameraFrame::~LatestCameraFrame() { stop(); }
 
    void LatestCameraFrame::start(mxvk::VK_Capture &source) {
        stop();
        {
            std::lock_guard<std::mutex> lock(frame_mutex);
            capture_source = &source;
            stopping = false;
            latest_frame.release();
            published_generation = 0;
            consumed_generation = 0;
        }
        capture_thread = std::thread(&LatestCameraFrame::captureLoop, this);
    }
 
    void LatestCameraFrame::stop() noexcept {
        {
            std::lock_guard<std::mutex> lock(frame_mutex);
            stopping = true;
        }
        frame_condition.notify_all();
        if (capture_thread.joinable()) {
            capture_thread.join();
        }
        std::lock_guard<std::mutex> lock(frame_mutex);
        capture_source = nullptr;
        latest_frame.release();
        published_generation = 0;
        consumed_generation = 0;
    }
 
    bool LatestCameraFrame::takeLatest(cv::Mat &frame, bool wait_for_first) {
        std::unique_lock<std::mutex> lock(frame_mutex);
        if (wait_for_first && published_generation == 0 && !stopping) {
            frame_condition.wait_for(lock, std::chrono::seconds(3), [&] { return stopping || published_generation > 0; });
        }
        if (stopping || published_generation == consumed_generation || latest_frame.empty()) {
            return false;
        }
        frame = latest_frame;
        consumed_generation = published_generation;
        return true;
    }
 
    void LatestCameraFrame::captureLoop() noexcept {
        while (true) {
            mxvk::VK_Capture *source = nullptr;
            {
                std::lock_guard<std::mutex> lock(frame_mutex);
                if (stopping) {
                    return;
                }
                source = capture_source;
            }
            if (source == nullptr) {
                return;
            }
 
            cv::Mat captured;
            bool read_frame = false;
            try {
                read_frame = source->read(captured);
            } catch (const std::exception &error) {
                std::cerr << "acmxvk: asynchronous camera read failed: " << error.what() << '\n';
            } catch (...) {
                std::cerr << "acmxvk: asynchronous camera read failed\n";
            }
            if (!read_frame || captured.empty()) {
                std::this_thread::sleep_for(std::chrono::milliseconds(5));
                continue;
            }
 
            {
                std::lock_guard<std::mutex> lock(frame_mutex);
                if (stopping) {
                    return;
                }
                latest_frame = std::move(captured);
                ++published_generation;
            }
            frame_condition.notify_one();
        }
    }
} // namespace acmxvk