ScreenCaptureReader.cpp

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// Copyright (c) 2008-2026 OpenShot Studios, LLC
//
// SPDX-License-Identifier: LGPL-3.0-or-later
 
#include "ScreenCaptureReader.h"
 
#include <algorithm>
#include <cctype>
#include <chrono>
#include <condition_variable>
#include <cstdlib>
#include <deque>
#include <limits>
#include <mutex>
#include <sstream>
#include <thread>
#include <vector>
 
#if defined(__linux__)
    #include <dlfcn.h>
#endif
 
extern "C" {
    #include <libavdevice/avdevice.h>
    #include <libavutil/imgutils.h>
}
 
#if defined(_WIN32)
    // Instantiate the Core Audio COM GUIDs in this translation unit. Older
    // MinGW-w64 uuid import libraries do not provide all WASAPI identifiers.
    #include <initguid.h>
    #include <audioclient.h>
    #include <mmdeviceapi.h>
#endif
 
#include "Exceptions.h"
#include "Frame.h"
#include "QtUtilities.h"
 
using namespace openshot;
 
#if defined(HAVE_WAYLAND_CAPTURE_PLUGIN) && defined(__linux__)
namespace
{
    using WaylandBackendFactory = std::unique_ptr<ScreenCaptureReader::CaptureBackendReader> (*) (
        const ScreenCaptureSettings&, ReaderInfo&);
 
    void* load_wayland_capture_backend(std::string& error_message)
    {
        Dl_info library_info {};
        if (dladdr(reinterpret_cast<void*>(load_wayland_capture_backend), &library_info)
            && library_info.dli_fname) {
            std::string library_path(library_info.dli_fname);
            const auto separator = library_path.find_last_of('/');
            if (separator != std::string::npos) {
                const std::string module_path = library_path.substr(0, separator + 1)
                    + "libopenshot-wayland-capture.so";
                if (void* module = dlopen(module_path.c_str(), RTLD_NOW | RTLD_LOCAL)) {
                    return module;
                }
                const char* error = dlerror();
                error_message = error ? error : "unable to load PipeWire support.";
                return nullptr;
            }
        }
        void* module = dlopen("libopenshot-wayland-capture.so", RTLD_NOW | RTLD_LOCAL);
        if (!module) {
            const char* error = dlerror();
            error_message = error ? error : "unable to load PipeWire support.";
        }
        return module;
    }
}
#endif
 
#if defined(__linux__)
class ScreenCaptureReader::SystemAudioCapture
{
public:
    explicit SystemAudioCapture(const ScreenCaptureSettings& new_settings)
        : settings(new_settings) {}
 
    ~SystemAudioCapture() { Close(); }
 
    void Open()
    {
        if (format_context) return;
        avdevice_register_all();
        AVInputFormat* input_format = const_cast<AVInputFormat*>(av_find_input_format("pulse"));
        if (!input_format) {
            throw InvalidOptions("FFmpeg PulseAudio input is unavailable for system audio capture.");
        }
 
        format_context = avformat_alloc_context();
        if (!format_context) {
            throw OutOfMemory("Unable to allocate system audio capture context.");
        }
        format_context->interrupt_callback.callback = InterruptCallback;
        format_context->interrupt_callback.opaque = &close_requested;
 
        AVDictionary* options = nullptr;
        av_dict_set(&options, "sample_rate", std::to_string(settings.audio_sample_rate).c_str(), 0);
        av_dict_set(&options, "channels", std::to_string(settings.audio_channels).c_str(), 0);
        const std::string device = settings.audio_device.empty() ? "@DEFAULT_MONITOR@" : settings.audio_device;
        const int open_result = avformat_open_input(&format_context, device.c_str(), input_format, &options);
        av_dict_free(&options);
        if (open_result < 0) {
            throw InvalidFile("Unable to open system audio capture input: " + std::string(av_err2str(open_result)), device);
        }
        if (avformat_find_stream_info(format_context, nullptr) < 0) {
            throw InvalidFile("Unable to read system audio capture stream information.", device);
        }
        for (unsigned int index = 0; index < format_context->nb_streams; ++index) {
            if (format_context->streams[index]->codecpar->codec_type == AVMEDIA_TYPE_AUDIO) {
                audio_stream = static_cast<int>(index);
                break;
            }
        }
        if (audio_stream < 0) {
            throw InvalidFile("No audio stream found in system audio capture input.", device);
        }
        AVStream* stream = format_context->streams[audio_stream];
        const AVCodec* codec = avcodec_find_decoder(stream->codecpar->codec_id);
        codec_context = codec ? ffmpeg_get_codec_context(stream, codec) : nullptr;
        if (!codec_context || avcodec_open2(codec_context, codec, nullptr) < 0) {
            throw InvalidCodec("Unable to open system audio capture decoder.", device);
        }
        packet = av_packet_alloc();
        decoded_frame = av_frame_alloc();
        if (!packet || !decoded_frame) {
            throw OutOfMemory("Unable to allocate system audio capture buffers.");
        }
        settings.audio_sample_rate = codec_context->sample_rate > 0
            ? codec_context->sample_rate : settings.audio_sample_rate;
        channels.assign(settings.audio_channels, {});
        close_requested = false;
        worker = std::thread(&SystemAudioCapture::CaptureLoop, this);
    }
 
    void Close()
    {
        close_requested = true;
        ready.notify_all();
        if (worker.joinable()) {
            worker.join();
        }
        if (decoded_frame) av_frame_free(&decoded_frame);
        if (packet) av_packet_free(&packet);
        if (codec_context) avcodec_free_context(&codec_context);
        if (format_context) avformat_close_input(&format_context);
    }
 
    void AddFrameAudio(const std::shared_ptr<Frame>& frame, int64_t number, const Fraction& fps)
    {
        int sample_count = 0;
        for (int64_t frame_number = last_output_frame + 1; frame_number <= number; ++frame_number) {
            sample_count += Frame::GetSamplesPerFrame(
                frame_number, fps, settings.audio_sample_rate, settings.audio_channels);
        }
        last_output_frame = std::max(last_output_frame, number);
        if (!frame || sample_count <= 0) return;
 
        std::unique_lock<std::mutex> lock(queue_mutex);
        // The capture backend commonly delivers its first buffer later than the
        // first video frame.  Writing silence after the old 100 ms timeout moved
        // every subsequently-delivered sample later on the recording timeline.
        // Allow the first frame to establish the audio epoch before falling back
        // to the short steady-state wait used for later frames.
        const auto wait_time = timeline_started
            ? std::chrono::milliseconds(100)
            : std::chrono::milliseconds(3000);
        ready.wait_for(lock, wait_time, [this, sample_count]() {
            return close_requested || (!channels.empty() && static_cast<int>(channels[0].size()) >= sample_count);
        });
        if (!channels.empty() && static_cast<int>(channels[0].size()) >= sample_count) {
            timeline_started = true;
        }
        frame->SampleRate(settings.audio_sample_rate);
        frame->ChannelsLayout(settings.audio_channels == 1 ? LAYOUT_MONO : LAYOUT_STEREO);
        for (int channel = 0; channel < settings.audio_channels; ++channel) {
            std::vector<float> samples(sample_count, 0.0f);
            if (channel < static_cast<int>(channels.size())) {
                const int available = std::min(sample_count, static_cast<int>(channels[channel].size()));
                for (int index = 0; index < available; ++index) {
                    samples[index] = channels[channel].front();
                    channels[channel].pop_front();
                }
            }
            frame->AddAudio(true, channel, 0, samples.data(), sample_count, 1.0f);
        }
    }
 
    void Reset()
    {
        std::lock_guard<std::mutex> lock(queue_mutex);
        for (auto& channel : channels) channel.clear();
        last_output_frame = 0;
        timeline_started = false;
    }
 
    int SampleRate() const { return settings.audio_sample_rate; }
    int Channels() const { return settings.audio_channels; }
 
private:
    static int InterruptCallback(void* opaque)
    {
        const auto* requested = static_cast<std::atomic<bool>*>(opaque);
        return requested && requested->load() ? 1 : 0;
    }
 
    float SampleAt(const AVFrame* frame, int channel, int sample) const
    {
        const AVSampleFormat format = static_cast<AVSampleFormat>(frame->format);
        const bool planar = av_sample_fmt_is_planar(format) != 0;
        const int source_channels = std::max(1,
#if HAVE_CH_LAYOUT
            codec_context->ch_layout.nb_channels
#else
            codec_context->channels
#endif
        );
        const int source_channel = std::min(channel, source_channels - 1);
        const uint8_t* data = planar ? frame->extended_data[source_channel] : frame->extended_data[0];
        const int offset = planar ? sample : sample * source_channels + source_channel;
        switch (format) {
        case AV_SAMPLE_FMT_U8: case AV_SAMPLE_FMT_U8P:
            return (static_cast<const uint8_t*>(static_cast<const void*>(data))[offset] - 128) / 128.0f;
        case AV_SAMPLE_FMT_S16: case AV_SAMPLE_FMT_S16P:
            return static_cast<const int16_t*>(static_cast<const void*>(data))[offset] / 32768.0f;
        case AV_SAMPLE_FMT_S32: case AV_SAMPLE_FMT_S32P:
            return static_cast<float>(static_cast<const int32_t*>(static_cast<const void*>(data))[offset] / 2147483648.0);
        case AV_SAMPLE_FMT_FLT: case AV_SAMPLE_FMT_FLTP:
            return static_cast<const float*>(static_cast<const void*>(data))[offset];
        case AV_SAMPLE_FMT_DBL: case AV_SAMPLE_FMT_DBLP:
            return static_cast<float>(static_cast<const double*>(static_cast<const void*>(data))[offset]);
        default:
            return 0.0f;
        }
    }
 
    void CaptureLoop()
    {
        while (!close_requested) {
            const int read_result = av_read_frame(format_context, packet);
            if (read_result == AVERROR(EAGAIN)) continue;
            if (read_result < 0) break;
            if (packet->stream_index != audio_stream) {
                av_packet_unref(packet);
                continue;
            }
            const int send_result = avcodec_send_packet(codec_context, packet);
            av_packet_unref(packet);
            if (send_result < 0) continue;
            while (avcodec_receive_frame(codec_context, decoded_frame) == 0) {
                std::lock_guard<std::mutex> lock(queue_mutex);
                for (int channel = 0; channel < settings.audio_channels; ++channel) {
                    const size_t max_samples = static_cast<size_t>(settings.audio_sample_rate) * 10;
                    for (int sample = 0; sample < decoded_frame->nb_samples; ++sample) {
                        if (channels[channel].size() >= max_samples) channels[channel].pop_front();
                        channels[channel].push_back(SampleAt(decoded_frame, channel, sample));
                    }
                }
                av_frame_unref(decoded_frame);
                ready.notify_all();
            }
        }
    }
 
    ScreenCaptureSettings settings;
    AVFormatContext* format_context = nullptr;
    AVCodecContext* codec_context = nullptr;
    AVPacket* packet = nullptr;
    AVFrame* decoded_frame = nullptr;
    int audio_stream = -1;
    std::atomic<bool> close_requested { false };
    std::thread worker;
    std::mutex queue_mutex;
    std::condition_variable ready;
    std::vector<std::deque<float>> channels;
    int64_t last_output_frame = 0;
    bool timeline_started = false;
};
#elif defined(_WIN32)
class ScreenCaptureReader::SystemAudioCapture
{
public:
    explicit SystemAudioCapture(const ScreenCaptureSettings& new_settings)
        : settings(new_settings) {}
 
    ~SystemAudioCapture() { Close(); }
 
    void Open()
    {
        if (worker.joinable()) return;
        close_requested = false;
        worker = std::thread(&SystemAudioCapture::CaptureLoop, this);
        std::unique_lock<std::mutex> lock(state_mutex);
        state_ready.wait_for(lock, std::chrono::seconds(5), [this]() { return opened || failed; });
        if (!opened) {
            close_requested = true;
            lock.unlock();
            if (worker.joinable()) worker.join();
            throw InvalidOptions(error.empty() ? "Unable to open WASAPI system audio loopback capture." : error);
        }
    }
 
    void Close()
    {
        close_requested = true;
        ready.notify_all();
        if (worker.joinable()) worker.join();
        opened = false;
    }
 
    void AddFrameAudio(const std::shared_ptr<Frame>& frame, int64_t number, const Fraction& fps)
    {
        int sample_count = 0;
        for (int64_t frame_number = last_output_frame + 1; frame_number <= number; ++frame_number) {
            sample_count += Frame::GetSamplesPerFrame(frame_number, fps, sample_rate, channel_count);
        }
        last_output_frame = std::max(last_output_frame, number);
        if (!frame || sample_count <= 0) return;
        std::unique_lock<std::mutex> lock(queue_mutex);
        // WASAPI can take longer than one video-frame interval to make its first
        // loopback packet available. Keep that startup latency out of the encoded
        // media timeline by waiting for the first complete frame of audio.
        const auto wait_time = timeline_started
            ? std::chrono::milliseconds(100)
            : std::chrono::milliseconds(3000);
        ready.wait_for(lock, wait_time, [this, sample_count]() {
            return close_requested || (!channels.empty() && static_cast<int>(channels[0].size()) >= sample_count);
        });
        if (!channels.empty() && static_cast<int>(channels[0].size()) >= sample_count) {
            timeline_started = true;
        }
        frame->SampleRate(sample_rate);
        frame->ChannelsLayout(channel_count == 1 ? LAYOUT_MONO : LAYOUT_STEREO);
        for (int channel = 0; channel < channel_count; ++channel) {
            std::vector<float> samples(sample_count, 0.0f);
            const int available = std::min(sample_count, static_cast<int>(channels[channel].size()));
            for (int index = 0; index < available; ++index) {
                samples[index] = channels[channel].front();
                channels[channel].pop_front();
            }
            frame->AddAudio(true, channel, 0, samples.data(), sample_count, 1.0f);
        }
    }
 
    void Reset()
    {
        std::lock_guard<std::mutex> lock(queue_mutex);
        for (auto& channel : channels) channel.clear();
        last_output_frame = 0;
        timeline_started = false;
    }
 
    int SampleRate() const { return sample_rate; }
    int Channels() const { return channel_count; }
 
private:
    template <typename T> static void Release(T*& value)
    {
        if (value) { value->Release(); value = nullptr; }
    }
 
    void Fail(const std::string& message)
    {
        std::lock_guard<std::mutex> lock(state_mutex);
        error = message;
        failed = true;
        state_ready.notify_all();
    }
 
    void CaptureLoop()
    {
        IMMDeviceEnumerator* enumerator = nullptr;
        IMMDevice* device = nullptr;
        IAudioClient* client = nullptr;
        IAudioCaptureClient* capture = nullptr;
        WAVEFORMATEX* format = nullptr;
        const HRESULT com_result = CoInitializeEx(nullptr, COINIT_MULTITHREADED);
        const bool uninitialize_com = SUCCEEDED(com_result);
        HRESULT result = CoCreateInstance(CLSID_MMDeviceEnumerator, nullptr, CLSCTX_ALL,
            IID_IMMDeviceEnumerator, reinterpret_cast<void**>(&enumerator));
        if (SUCCEEDED(result)) {
            result = enumerator->GetDefaultAudioEndpoint(eRender, eConsole, &device);
        }
        if (SUCCEEDED(result)) {
            result = device->Activate(IID_IAudioClient, CLSCTX_ALL, nullptr, reinterpret_cast<void**>(&client));
        }
        if (SUCCEEDED(result)) result = client->GetMixFormat(&format);
        if (SUCCEEDED(result)) {
            result = client->Initialize(AUDCLNT_SHAREMODE_SHARED, AUDCLNT_STREAMFLAGS_LOOPBACK,
                0, 0, format, nullptr);
        }
        if (SUCCEEDED(result)) {
            result = client->GetService(IID_IAudioCaptureClient, reinterpret_cast<void**>(&capture));
        }
        if (SUCCEEDED(result)) result = client->Start();
        if (FAILED(result) || !format || !capture) {
            Fail("Unable to initialize WASAPI system audio loopback capture (HRESULT " + std::to_string(result) + ").");
            if (format) CoTaskMemFree(format);
            Release(capture); Release(client); Release(device); Release(enumerator);
            if (uninitialize_com) CoUninitialize();
            return;
        }
 
        sample_rate = static_cast<int>(format->nSamplesPerSec);
        channel_count = std::max(1, std::min(2, static_cast<int>(format->nChannels)));
        channels.assign(channel_count, {});
        bool floating_point = format->wFormatTag == WAVE_FORMAT_IEEE_FLOAT;
        if (format->wFormatTag == WAVE_FORMAT_EXTENSIBLE && format->cbSize >= 22) {
            const auto* extensible = reinterpret_cast<const WAVEFORMATEXTENSIBLE*>(format);
            floating_point = extensible->SubFormat.Data1 == WAVE_FORMAT_IEEE_FLOAT;
        }
        {
            std::lock_guard<std::mutex> lock(state_mutex);
            opened = true;
            state_ready.notify_all();
        }
 
        while (!close_requested) {
            UINT32 packet_frames = 0;
            if (FAILED(capture->GetNextPacketSize(&packet_frames))) break;
            if (packet_frames == 0) {
                std::this_thread::sleep_for(std::chrono::milliseconds(2));
                continue;
            }
            BYTE* data = nullptr;
            UINT32 frames = 0;
            DWORD flags = 0;
            if (FAILED(capture->GetBuffer(&data, &frames, &flags, nullptr, nullptr))) break;
            {
                std::lock_guard<std::mutex> lock(queue_mutex);
                for (UINT32 frame_index = 0; frame_index < frames; ++frame_index) {
                    for (int channel = 0; channel < channel_count; ++channel) {
                        float sample = 0.0f;
                        if (!(flags & AUDCLNT_BUFFERFLAGS_SILENT) && data) {
                            const int offset = static_cast<int>(frame_index) * format->nChannels + channel;
                            if (floating_point && format->wBitsPerSample == 32) {
                                sample = reinterpret_cast<const float*>(data)[offset];
                            } else if (format->wBitsPerSample == 16) {
                                sample = reinterpret_cast<const int16_t*>(data)[offset] / 32768.0f;
                            } else if (format->wBitsPerSample == 32) {
                                sample = static_cast<float>(reinterpret_cast<const int32_t*>(data)[offset] / 2147483648.0);
                            }
                        }
                        const size_t max_samples = static_cast<size_t>(sample_rate) * 10;
                        if (channels[channel].size() >= max_samples) channels[channel].pop_front();
                        channels[channel].push_back(sample);
                    }
                }
            }
            capture->ReleaseBuffer(frames);
            ready.notify_all();
        }
 
        client->Stop();
        CoTaskMemFree(format);
        Release(capture); Release(client); Release(device); Release(enumerator);
        if (uninitialize_com) CoUninitialize();
    }
 
    ScreenCaptureSettings settings;
    std::atomic<bool> close_requested { false };
    std::thread worker;
    std::mutex queue_mutex;
    std::condition_variable ready;
    std::vector<std::deque<float>> channels;
    int64_t last_output_frame = 0;
    bool timeline_started = false;
    int sample_rate = 48000;
    int channel_count = 2;
    std::mutex state_mutex;
    std::condition_variable state_ready;
    bool opened = false;
    bool failed = false;
    std::string error;
};
#else
class ScreenCaptureReader::SystemAudioCapture
{
public:
    explicit SystemAudioCapture(const ScreenCaptureSettings&) {}
    void Open() {}
    void Close() {}
    void AddFrameAudio(const std::shared_ptr<Frame>&, int64_t, const Fraction&) {}
    void Reset() {}
    int SampleRate() const { return 0; }
    int Channels() const { return 0; }
};
#endif
 
namespace
{
    std::string fraction_to_string(const Fraction& value)
    {
        std::stringstream stream;
        stream << value.num << "/" << value.den;
        return stream.str();
    }
 
    void set_option(AVDictionary** options, const std::string& key, const std::string& value)
    {
        av_dict_set(options, key.c_str(), value.c_str(), 0);
    }
 
    bool option_enabled(const std::map<std::string, std::string>& options, const std::string& key)
    {
        const auto option = options.find(key);
        if (option == options.end()) {
            return false;
        }
        return option->second == "1" || option->second == "true" || option->second == "yes";
    }
 
    int option_int(const std::map<std::string, std::string>& options, const std::string& key, int fallback)
    {
        const auto option = options.find(key);
        if (option == options.end()) {
            return fallback;
        }
        try {
            return std::stoi(option->second);
        } catch (...) {
            return fallback;
        }
    }
 
    int capture_interrupt_callback(void* opaque)
    {
        const auto* reader = static_cast<std::atomic<bool>*>(opaque);
        return reader && reader->load() ? 1 : 0;
    }
 
    std::string avfoundation_video_name(const std::string& input_name)
    {
        const size_t separator = input_name.find(':');
        return separator == std::string::npos ? input_name : input_name.substr(0, separator);
    }
 
    std::string avfoundation_audio_name(const std::string& input_name)
    {
        const size_t separator = input_name.find(':');
        return separator == std::string::npos ? "none" : input_name.substr(separator + 1);
    }
 
    bool resolve_avfoundation_video_index(
        AVInputFormat* input_format,
        const std::string& video_name,
        std::string& video_index)
    {
        const auto is_digit = [](unsigned char value) {
            return std::isdigit(value) != 0;
        };
        if (video_name.empty()
            || video_name == "default"
            || video_name == "none"
            || std::all_of(video_name.begin(), video_name.end(), is_digit)) {
            return false;
        }
 
        AVDeviceInfoList* device_list = nullptr;
        const int result = avdevice_list_input_sources(input_format, nullptr, nullptr, &device_list);
        if (result < 0 || !device_list) {
            avdevice_free_list_devices(&device_list);
            return false;
        }
 
        bool found = false;
        for (int index = 0; index < device_list->nb_devices; ++index) {
            const AVDeviceInfo* device = device_list->devices[index];
            if (!device || !device->device_name) {
                continue;
            }
            const std::string name = device->device_name;
            const std::string description = device->device_description
                ? device->device_description
                : device->device_name;
            if (video_name == name || video_name == description) {
                video_index = std::all_of(name.begin(), name.end(), is_digit)
                    ? name
                    : std::to_string(index);
                found = true;
                break;
            }
        }
        avdevice_free_list_devices(&device_list);
        return found;
    }
}
 
ScreenCaptureReader::ScreenCaptureReader(const ScreenCaptureSettings& new_settings)
    : settings(new_settings)
    , backend_reader(nullptr)
    , backend_module(nullptr)
    , is_open(false)
    , video_stream(-1)
    , frames_read(0)
    , dropped_packets(0)
    , format_context(nullptr)
    , codec_context(nullptr)
    , source_frame(nullptr)
    , rgba_frame(nullptr)
    , packet(nullptr)
    , sws_context(nullptr)
    , close_requested(false)
    , system_audio(nullptr)
{
    if (settings.backend == SCREEN_CAPTURE_AUTO) {
        settings.backend = DefaultBackend();
    }
    ValidateSettings();
    PopulateInfo();
#if defined(__linux__) || defined(_WIN32)
    if (settings.capture_audio) {
        system_audio = std::make_unique<SystemAudioCapture>(settings);
    }
#endif
    if (UsesWaylandPortal()) {
    #if defined(HAVE_WAYLAND_CAPTURE_PLUGIN) && defined(__linux__)
        std::string module_error;
        backend_module = load_wayland_capture_backend(module_error);
        if (!backend_module) {
            throw InvalidOptions("Wayland screen capture backend is unavailable: "
                + module_error);
        }
        auto factory = reinterpret_cast<WaylandBackendFactory>(
            dlsym(backend_module, "OpenShotCreateWaylandScreenCaptureReader"));
        if (!factory) {
            const char* error = dlerror();
            dlclose(backend_module);
            backend_module = nullptr;
            throw InvalidOptions("Wayland screen capture backend is invalid: "
                + std::string(error ? error : "factory function is missing."));
        }
        try {
            backend_reader = factory(settings, info);
        } catch (...) {
            dlclose(backend_module);
            backend_module = nullptr;
            throw;
        }
        if (!backend_reader) {
            dlclose(backend_module);
            backend_module = nullptr;
            throw InvalidOptions("Wayland screen capture backend is unavailable.");
        }
    #else
        throw InvalidOptions("Wayland screen capture backend is unavailable in this build.");
    #endif
    }
}
 
ScreenCaptureReader::~ScreenCaptureReader()
{
    Close();
#if defined(__linux__)
    backend_reader.reset();
    if (backend_module) {
        dlclose(backend_module);
        backend_module = nullptr;
    }
#endif
}
 
bool ScreenCaptureReader::IsOpen()
{
    const std::lock_guard<std::recursive_mutex> lock(getFrameMutex);
    return backend_reader ? backend_reader->IsOpen() : is_open;
}
 
bool ScreenCaptureReader::IsBackendSupported(ScreenCaptureBackend backend)
{
#if defined(__linux__)
    if (backend == SCREEN_CAPTURE_X11 || backend == SCREEN_CAPTURE_AUTO) {
        return true;
    }
#if defined(HAVE_WAYLAND_CAPTURE_PLUGIN)
    if (backend == SCREEN_CAPTURE_WAYLAND) {
        return true;
    }
#endif
    return false;
#elif defined(_WIN32)
    return backend == SCREEN_CAPTURE_WINDOWS_GDI || backend == SCREEN_CAPTURE_AUTO;
#elif defined(__APPLE__)
    return backend == SCREEN_CAPTURE_MAC_AVFOUNDATION || backend == SCREEN_CAPTURE_AUTO;
#else
    (void) backend;
    return false;
#endif
}
 
bool ScreenCaptureReader::IsSystemAudioSupported(ScreenCaptureBackend backend)
{
#if defined(__linux__)
    if (backend == SCREEN_CAPTURE_AUTO) {
        backend = DefaultBackend();
    }
    avdevice_register_all();
    return (backend == SCREEN_CAPTURE_X11 || backend == SCREEN_CAPTURE_WAYLAND)
        && av_find_input_format("pulse") != nullptr;
#elif defined(_WIN32)
    return backend == SCREEN_CAPTURE_AUTO || backend == SCREEN_CAPTURE_WINDOWS_GDI;
#else
    (void) backend;
    return false;
#endif
}
 
ScreenCaptureBackend ScreenCaptureReader::DefaultBackend()
{
#if defined(__linux__)
    const char* session = std::getenv("XDG_SESSION_TYPE");
    if (session && std::string(session) == "wayland" && IsBackendSupported(SCREEN_CAPTURE_WAYLAND)) {
        return SCREEN_CAPTURE_WAYLAND;
    }
    if (!session || std::string(session) == "x11") {
        return SCREEN_CAPTURE_X11;
    }
#elif defined(_WIN32)
    return SCREEN_CAPTURE_WINDOWS_GDI;
#elif defined(__APPLE__)
    return SCREEN_CAPTURE_MAC_AVFOUNDATION;
#endif
    return SCREEN_CAPTURE_AUTO;
}
 
void ScreenCaptureReader::ValidateSettings() const
{
    if (!IsBackendSupported(settings.backend)) {
        throw InvalidOptions("Screen capture backend is not supported on this OS or session.");
    }
    if (!UsesFFmpegDevice() && !UsesWaylandPortal()) {
        throw InvalidOptions("Screen capture backend is not implemented in this build.");
    }
    if (settings.width <= 0 || settings.height <= 0) {
        throw InvalidOptions("Screen capture requires a positive width and height.");
    }
    if (settings.fps.num <= 0 || settings.fps.den <= 0) {
        throw InvalidOptions("Screen capture requires a positive frame rate.");
    }
    if (settings.capture_audio && !IsSystemAudioSupported(settings.backend)) {
        throw InvalidOptions("System audio capture is not supported by this screen capture backend.");
    }
    if (settings.audio_sample_rate < 8000) {
        throw InvalidSampleRate("System audio capture requires a sample rate of at least 8000 Hz.");
    }
    if (settings.audio_channels < 1 || settings.audio_channels > 2) {
        throw InvalidChannels("System audio capture requires one or two channels.");
    }
}
 
bool ScreenCaptureReader::UsesFFmpegDevice() const
{
    return settings.backend == SCREEN_CAPTURE_X11
        || settings.backend == SCREEN_CAPTURE_WINDOWS_GDI
        || settings.backend == SCREEN_CAPTURE_MAC_AVFOUNDATION
        || settings.options.count("input_format_name");
}
 
bool ScreenCaptureReader::UsesWaylandPortal() const
{
    return settings.backend == SCREEN_CAPTURE_WAYLAND;
}
 
std::string ScreenCaptureReader::InputFormatName() const
{
    const auto override_format = settings.options.find("input_format_name");
    if (override_format != settings.options.end()) {
        return override_format->second;
    }
    if (settings.backend == SCREEN_CAPTURE_X11) {
        return "x11grab";
    }
    if (settings.backend == SCREEN_CAPTURE_WINDOWS_GDI) {
        return "gdigrab";
    }
    if (settings.backend == SCREEN_CAPTURE_MAC_AVFOUNDATION) {
        return "avfoundation";
    }
    return "";
}
 
std::string ScreenCaptureReader::InputName() const
{
    if (InputFormatName() == "v4l2") {
        return settings.display.empty() ? "/dev/video0" : settings.display;
    }
    if (InputFormatName() == "dshow") {
        return settings.display;
    }
    if (InputFormatName() == "gdigrab") {
        return settings.display.empty() ? "desktop" : settings.display;
    }
    if (InputFormatName() == "avfoundation") {
        return settings.display.empty() ? "Capture screen 0:none" : settings.display;
    }
 
    std::string display = settings.display;
    if (display.empty()) {
        const char* env_display = std::getenv("DISPLAY");
        display = env_display ? env_display : ":0.0";
    }
    if (InputFormatName() == "x11grab" && settings.options.count("window_id")) {
        return display;
    }
 
    std::stringstream input;
    input << display << "+" << settings.x << "," << settings.y;
    return input.str();
}
 
void ScreenCaptureReader::PopulateInfo()
{
    info.has_video = true;
    info.has_audio = settings.capture_audio;
    info.has_single_image = false;
    info.duration = 60.0f * 60.0f;
    info.file_size = 0;
    info.width = settings.width;
    info.height = settings.height;
    info.pixel_format = AV_PIX_FMT_RGBA;
    info.fps = settings.fps;
    info.video_bit_rate = 0;
    info.pixel_ratio = Fraction(1, 1);
    info.display_ratio = Fraction(settings.width, settings.height);
    info.display_ratio.Reduce();
    info.vcodec = "rawvideo";
    info.video_length = static_cast<int64_t>(info.duration * settings.fps.ToFloat());
    info.video_stream_index = -1;
    info.video_timebase = settings.fps.Reciprocal();
    info.interlaced_frame = false;
    info.top_field_first = false;
    info.acodec = settings.capture_audio ? "pcm_f32le" : "";
    info.audio_bit_rate = 0;
    info.sample_rate = settings.capture_audio ? settings.audio_sample_rate : 0;
    info.channels = settings.capture_audio ? settings.audio_channels : 0;
    info.channel_layout = settings.audio_channels == 2 ? LAYOUT_STEREO : LAYOUT_MONO;
    info.audio_stream_index = -1;
    info.audio_timebase = Fraction(1, 1);
}
 
void ScreenCaptureReader::Open()
{
    if (backend_reader) {
        if (backend_reader->IsOpen()) return;
        manual_system_audio = false;
        if (system_audio) {
            system_audio->Open();
            info.sample_rate = system_audio->SampleRate();
            info.channels = system_audio->Channels();
            info.channel_layout = info.channels == 1 ? LAYOUT_MONO : LAYOUT_STEREO;
        }
        try {
            backend_reader->Open();
        } catch (...) {
            if (system_audio) system_audio->Close();
            throw;
        }
        return;
    }
    if (is_open) {
        return;
    }
    manual_system_audio = false;
    if (system_audio) {
        system_audio->Open();
        info.sample_rate = system_audio->SampleRate();
        info.channels = system_audio->Channels();
        info.channel_layout = info.channels == 1 ? LAYOUT_MONO : LAYOUT_STEREO;
    }
    close_requested = false;
    try {
        OpenDevice();
        OpenDecoder();
    } catch (...) {
        if (system_audio) system_audio->Close();
        throw;
    }
    is_open = true;
}
 
void ScreenCaptureReader::OpenDevice()
{
    avdevice_register_all();
 
    AVInputFormat* input_format = const_cast<AVInputFormat*>(av_find_input_format(InputFormatName().c_str()));
    std::string input_name = InputName();
    if (!input_format) {
        throw InvalidOptions("FFmpeg input device is not available: " + InputFormatName(), input_name);
    }
 
    format_context = avformat_alloc_context();
    if (!format_context) {
        throw OutOfMemory("Unable to allocate capture format context.", input_name);
    }
    format_context->interrupt_callback.callback = capture_interrupt_callback;
    format_context->interrupt_callback.opaque = &close_requested;
 
    AVDictionary* options = nullptr;
    const bool use_device_defaults = settings.options.count("use_device_defaults") > 0;
    const bool post_capture_crop = option_enabled(settings.options, "crop_after_capture");
    if (!use_device_defaults && !post_capture_crop) {
        set_option(&options, "framerate", fraction_to_string(settings.fps));
        set_option(&options, "video_size", std::to_string(settings.width) + "x" + std::to_string(settings.height));
    } else if (post_capture_crop) {
        const int source_width = option_int(settings.options, "crop_source_width", settings.width);
        const int source_height = option_int(settings.options, "crop_source_height", settings.height);
        set_option(&options, "framerate", fraction_to_string(settings.fps));
        set_option(&options, "video_size", std::to_string(source_width) + "x" + std::to_string(source_height));
    }
    if (InputFormatName() == "x11grab") {
        set_option(&options, "draw_mouse", settings.include_cursor ? "1" : "0");
        set_option(&options, "show_region", settings.show_region ? "1" : "0");
    } else if (InputFormatName() == "gdigrab") {
        set_option(&options, "draw_mouse", settings.include_cursor ? "1" : "0");
        set_option(&options, "show_region", settings.show_region ? "1" : "0");
        set_option(&options, "offset_x", std::to_string(settings.x));
        set_option(&options, "offset_y", std::to_string(settings.y));
    } else if (InputFormatName() == "avfoundation") {
        set_option(&options, "capture_cursor", settings.include_cursor ? "1" : "0");
        std::string video_index;
        if (resolve_avfoundation_video_index(input_format, avfoundation_video_name(input_name), video_index)) {
            set_option(&options, "video_device_index", video_index);
            input_name = ":" + avfoundation_audio_name(input_name);
        }
    }
    for (const auto& option : settings.options) {
        if (option.first == "input_format_name"
            || option.first == "use_device_defaults"
            || option.first == "crop_after_capture"
            || option.first == "crop_source_width"
            || option.first == "crop_source_height") {
            continue;
        }
        set_option(&options, option.first, option.second);
    }
 
    const int result = avformat_open_input(&format_context, input_name.c_str(), input_format, &options);
    av_dict_free(&options);
    if (result < 0) {
        throw InvalidFile("Unable to open screen capture input: " + std::string(av_err2str(result)), input_name);
    }
}
 
void ScreenCaptureReader::OpenDecoder()
{
    if (avformat_find_stream_info(format_context, nullptr) < 0) {
        throw InvalidFile("Unable to read capture stream information.", InputName());
    }
 
    for (unsigned int index = 0; index < format_context->nb_streams; ++index) {
        if (format_context->streams[index]->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) {
            video_stream = static_cast<int>(index);
            break;
        }
    }
    if (video_stream < 0) {
        throw InvalidFile("No video stream found in capture input.", InputName());
    }
 
    AVStream* stream = format_context->streams[video_stream];
    const AVCodec* codec = avcodec_find_decoder(stream->codecpar->codec_id);
    if (!codec) {
        throw InvalidCodec("No decoder available for capture stream.", InputName());
    }
 
    codec_context = ffmpeg_get_codec_context(stream, codec);
    if (!codec_context || avcodec_open2(codec_context, codec, nullptr) < 0) {
        throw InvalidCodec("Unable to open capture stream decoder.", InputName());
    }
 
    info.width = codec_context->width > 0 ? codec_context->width : settings.width;
    info.height = codec_context->height > 0 ? codec_context->height : settings.height;
    if (option_enabled(settings.options, "crop_after_capture")) {
        info.width = settings.width;
        info.height = settings.height;
    }
    info.video_stream_index = video_stream;
    info.pixel_format = codec_context->pix_fmt;
    info.display_ratio = Fraction(info.width, info.height);
    info.display_ratio.Reduce();
    if (codec_context->framerate.num > 0 && codec_context->framerate.den > 0) {
        info.fps = Fraction(codec_context->framerate.num, codec_context->framerate.den);
        info.video_timebase = info.fps.Reciprocal();
    } else if (stream->avg_frame_rate.num > 0 && stream->avg_frame_rate.den > 0) {
        info.fps = Fraction(stream->avg_frame_rate.num, stream->avg_frame_rate.den);
        info.video_timebase = info.fps.Reciprocal();
    } else if (stream->r_frame_rate.num > 0 && stream->r_frame_rate.den > 0) {
        info.fps = Fraction(stream->r_frame_rate.num, stream->r_frame_rate.den);
        info.video_timebase = info.fps.Reciprocal();
    }
 
    source_frame = av_frame_alloc();
    rgba_frame = av_frame_alloc();
    packet = av_packet_alloc();
    if (!source_frame || !rgba_frame || !packet) {
        throw OutOfMemory("Unable to allocate capture decoder frames.", InputName());
    }
}
 
std::shared_ptr<Frame> ScreenCaptureReader::GetFrame(int64_t number)
{
    const std::lock_guard<std::recursive_mutex> lock(getFrameMutex);
    if (backend_reader) {
        if (!backend_reader->IsOpen()) {
            throw ReaderClosed("The ScreenCaptureReader is closed. Call Open() before GetFrame().");
        }
        auto frame = backend_reader->GetFrame(number);
        if (system_audio && !manual_system_audio) system_audio->AddFrameAudio(frame, number, info.fps);
        return frame;
    }
    if (!is_open) {
        throw ReaderClosed("The ScreenCaptureReader is closed. Call Open() before GetFrame().");
    }
 
    auto frame = DecodeNextFrame(number);
    if (system_audio && !manual_system_audio) system_audio->AddFrameAudio(frame, number, info.fps);
    return frame;
}
 
void ScreenCaptureReader::AddSystemAudio(std::shared_ptr<Frame> frame, int64_t output_frame_number)
{
    if (system_audio) {
        system_audio->AddFrameAudio(frame, output_frame_number, info.fps);
    }
}
 
void ScreenCaptureReader::ResetSystemAudio()
{
    manual_system_audio = true;
    if (system_audio) {
        system_audio->Reset();
    }
}
 
std::shared_ptr<Frame> ScreenCaptureReader::DecodeNextFrame(int64_t number)
{
    while (!close_requested) {
        const int read_result = av_read_frame(format_context, packet);
        if (read_result == AVERROR(EAGAIN)) {
            std::this_thread::sleep_for(std::chrono::milliseconds(5));
            continue;
        }
        if (read_result < 0) {
            const std::string message = frames_read > 0
                ? "Capture input ended after " + std::to_string(frames_read) + " frame(s): "
                : "Capture input ended before a frame could be read: ";
            throw InvalidFile(message + std::string(av_err2str(read_result)), InputName());
        }
 
        if (packet->stream_index != video_stream) {
            av_packet_unref(packet);
            dropped_packets++;
            continue;
        }
 
        const int64_t packet_timestamp = packet->pts != AV_NOPTS_VALUE ? packet->pts : packet->dts;
        const int send_result = avcodec_send_packet(codec_context, packet);
        av_packet_unref(packet);
        if (send_result < 0) {
            continue;
        }
 
        const int receive_result = avcodec_receive_frame(codec_context, source_frame);
        if (receive_result == AVERROR(EAGAIN)) {
            continue;
        }
        if (receive_result < 0) {
            throw InvalidFile("Unable to decode capture frame: " + std::string(av_err2str(receive_result)), InputName());
        }
 
        const AVStream* stream = format_context->streams[video_stream];
        int64_t frame_timestamp = source_frame->best_effort_timestamp;
        if (frame_timestamp == AV_NOPTS_VALUE) {
            frame_timestamp = source_frame->pts;
        }
        if (frame_timestamp == AV_NOPTS_VALUE) {
            frame_timestamp = packet_timestamp;
        }
        double capture_timestamp = std::numeric_limits<double>::quiet_NaN();
        if (frame_timestamp != AV_NOPTS_VALUE && stream) {
            capture_timestamp = static_cast<double>(frame_timestamp) * av_q2d(stream->time_base);
        }
 
        const int width = source_frame->width > 0 ? source_frame->width : info.width;
        const int height = source_frame->height > 0 ? source_frame->height : info.height;
        const PixelFormat src_fmt = static_cast<PixelFormat>(source_frame->format);
 
        sws_context = sws_getCachedContext(
            sws_context,
            width,
            height,
            src_fmt,
            width,
            height,
            AV_PIX_FMT_RGBA,
            SWS_BILINEAR,
            nullptr,
            nullptr,
            nullptr);
        if (!sws_context) {
            throw InvalidFile("Unable to create capture pixel conversion context.", InputName());
        }
 
        const int bytes_per_pixel = 4;
        const size_t buffer_size = static_cast<size_t>(width) * height * bytes_per_pixel;
        unsigned char* buffer = static_cast<unsigned char*>(aligned_malloc(buffer_size));
        if (!buffer) {
            throw OutOfMemory("Unable to allocate capture frame buffer.", InputName());
        }
 
        av_image_fill_arrays(rgba_frame->data, rgba_frame->linesize, buffer, AV_PIX_FMT_RGBA, width, height, 1);
        const int scaled_lines = sws_scale(sws_context, source_frame->data, source_frame->linesize, 0, height, rgba_frame->data, rgba_frame->linesize);
        av_frame_unref(source_frame);
 
        if (scaled_lines <= 0) {
            openshot::aligned_free(buffer);
            continue;
        }
 
        int output_width = width;
        int output_height = height;
        unsigned char* output_buffer = buffer;
        if (option_enabled(settings.options, "crop_after_capture")) {
            const int crop_x = std::max(0, std::min(settings.x, width - 1));
            const int crop_y = std::max(0, std::min(settings.y, height - 1));
            output_width = std::max(1, std::min(settings.width, width - crop_x));
            output_height = std::max(1, std::min(settings.height, height - crop_y));
            const size_t output_buffer_size = static_cast<size_t>(output_width) * output_height * bytes_per_pixel;
            output_buffer = static_cast<unsigned char*>(aligned_malloc(output_buffer_size));
            if (!output_buffer) {
                openshot::aligned_free(buffer);
                throw OutOfMemory("Unable to allocate cropped capture frame buffer.", InputName());
            }
            for (int row = 0; row < output_height; ++row) {
                const unsigned char* source_row = buffer
                    + (static_cast<size_t>(crop_y + row) * width + crop_x) * bytes_per_pixel;
                unsigned char* dest_row = output_buffer + static_cast<size_t>(row) * output_width * bytes_per_pixel;
                std::copy(source_row, source_row + static_cast<size_t>(output_width) * bytes_per_pixel, dest_row);
            }
            openshot::aligned_free(buffer);
        }
 
        auto frame = std::make_shared<Frame>(number, output_width, output_height, "#000000");
        frame->capture_timestamp = capture_timestamp;
        frame->AddImage(output_width, output_height, bytes_per_pixel, QImage::Format_RGBA8888, output_buffer);
        frames_read++;
        return frame;
    }
 
    throw ReaderClosed("The ScreenCaptureReader was closed.");
}
 
void ScreenCaptureReader::Close()
{
    // Signal blocking native reads before waiting for GetFrame(). The FFmpeg
    // interrupt callback observes close_requested, while backend readers use
    // Close() to wake their own blocking waits.
    close_requested = true;
    if (backend_reader) {
        backend_reader->Close();
    }
 
    // GetFrame() owns all decoder and system-audio use under this mutex. Do not
    // release those resources until an interrupted read has completely exited.
    const std::lock_guard<std::recursive_mutex> lock(getFrameMutex);
    if (system_audio) {
        system_audio->Close();
    }
    if (packet) {
        av_packet_free(&packet);
    }
    if (source_frame) {
        av_frame_free(&source_frame);
    }
    if (rgba_frame) {
        av_frame_free(&rgba_frame);
    }
    if (sws_context) {
        sws_freeContext(sws_context);
        sws_context = nullptr;
    }
    if (codec_context) {
        avcodec_free_context(&codec_context);
    }
    if (format_context) {
        avformat_close_input(&format_context);
    }
    is_open = false;
    video_stream = -1;
}
 
openshot::CaptureReaderStats ScreenCaptureReader::GetStats() const
{
    if (backend_reader) {
        return backend_reader->GetStats();
    }
    CaptureReaderStats stats;
    stats.is_open = is_open;
    stats.frames_read = frames_read;
    stats.dropped_packets = dropped_packets;
    const double fps = settings.fps.den != 0 ? static_cast<double>(settings.fps.num) / static_cast<double>(settings.fps.den) : 0.0;
    stats.duration = fps > 0.0 ? static_cast<double>(frames_read) / fps : 0.0;
    return stats;
}
 
std::string ScreenCaptureReader::Json() const
{
    return JsonValue().toStyledString();
}
 
Json::Value ScreenCaptureReader::JsonValue() const
{
    Json::Value root = ReaderBase::JsonValue();
    root["type"] = "ScreenCaptureReader";
    root["backend"] = settings.backend;
    root["display"] = settings.display;
    root["x"] = settings.x;
    root["y"] = settings.y;
    root["width"] = settings.width;
    root["height"] = settings.height;
    root["fps"]["num"] = settings.fps.num;
    root["fps"]["den"] = settings.fps.den;
    root["include_cursor"] = settings.include_cursor;
    root["show_region"] = settings.show_region;
    root["capture_audio"] = settings.capture_audio;
    root["audio_device"] = settings.audio_device;
    root["audio_sample_rate"] = settings.audio_sample_rate;
    root["audio_channels"] = settings.audio_channels;
    root["options"] = Json::Value(Json::objectValue);
    for (const auto& option : settings.options) {
        root["options"][option.first] = option.second;
    }
    return root;
}
 
void ScreenCaptureReader::SetJson(const std::string value)
{
    try {
        SetJsonValue(openshot::stringToJson(value));
    } catch (const std::exception&) {
        throw InvalidJSON("JSON is invalid (missing keys or invalid data types)");
    }
}
 
void ScreenCaptureReader::SetJsonValue(const Json::Value root)
{
    if (!root["backend"].isNull())
        settings.backend = static_cast<ScreenCaptureBackend>(root["backend"].asInt());
    if (!root["display"].isNull())
        settings.display = root["display"].asString();
    if (!root["x"].isNull())
        settings.x = root["x"].asInt();
    if (!root["y"].isNull())
        settings.y = root["y"].asInt();
    if (!root["width"].isNull())
        settings.width = root["width"].asInt();
    if (!root["height"].isNull())
        settings.height = root["height"].asInt();
    if (!root["fps"].isNull() && root["fps"].isObject()) {
        if (!root["fps"]["num"].isNull())
            settings.fps.num = root["fps"]["num"].asInt();
        if (!root["fps"]["den"].isNull())
            settings.fps.den = root["fps"]["den"].asInt();
    }
    if (!root["include_cursor"].isNull())
        settings.include_cursor = root["include_cursor"].asBool();
    if (!root["show_region"].isNull())
        settings.show_region = root["show_region"].asBool();
    if (!root["capture_audio"].isNull())
        settings.capture_audio = root["capture_audio"].asBool();
    if (!root["audio_device"].isNull())
        settings.audio_device = root["audio_device"].asString();
    if (!root["audio_sample_rate"].isNull())
        settings.audio_sample_rate = root["audio_sample_rate"].asInt();
    if (!root["audio_channels"].isNull())
        settings.audio_channels = root["audio_channels"].asInt();
    if (!root["options"].isNull() && root["options"].isObject()) {
        settings.options.clear();
        for (const auto& key : root["options"].getMemberNames()) {
            settings.options[key] = root["options"][key].asString();
        }
    }
    if (settings.backend == SCREEN_CAPTURE_AUTO) {
        settings.backend = DefaultBackend();
    }
    ValidateSettings();
    PopulateInfo();
#if defined(__linux__) || defined(_WIN32)
    system_audio.reset();
    if (settings.capture_audio) {
        system_audio = std::make_unique<SystemAudioCapture>(settings);
    }
#endif
}