qffmpegplaybackengine.cpp

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// Copyright (C) 2021 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
#include "qffmpegplaybackengine_p.h"
 
#include "qvideosink.h"
#include "qaudiooutput.h"
#include "private/qplatformaudiooutput_p.h"
#include "qiodevice.h"
#include "playbackengine/qffmpegdemuxer_p.h"
#include "playbackengine/qffmpegstreamdecoder_p.h"
#include "playbackengine/qffmpegsubtitlerenderer_p.h"
#include "playbackengine/qffmpegvideorenderer_p.h"
#include "playbackengine/qffmpegaudiorenderer_p.h"
 
#include <qloggingcategory.h>
 
QT_BEGIN_NAMESPACE
 
namespace QFFmpeg {
 
static Q_LOGGING_CATEGORY(qLcPlaybackEngine, "qt.multimedia.ffmpeg.playbackengine");
 
// The helper is needed since on some compilers std::unique_ptr
// doesn't have a default constructor in the case of sizeof(CustomDeleter) > 0
template<typename Array>
inline Array defaultObjectsArray()
{
    using T = typename Array::value_type;
    return { T{ {}, {} }, T{ {}, {} }, T{ {}, {} } };
}
 
// TODO: investigate what's better: profile and try network case
// Most likely, shouldPauseStreams = false is better because of:
//     - packet and frame buffers are not big, the saturration of the is pretty fast.
//     - after any pause a user has some preloaded buffers, so the playback is
//       supposed to be more stable in cases with a weak processor or bad internet.
//     - the code is simplier, usage is more convenient.
//
static constexpr bool shouldPauseStreams = false;
 
PlaybackEngine::PlaybackEngine()
    : m_demuxer({}, {}),
      m_streams(defaultObjectsArray<decltype(m_streams)>()),
      m_renderers(defaultObjectsArray<decltype(m_renderers)>())
{
    qCDebug(qLcPlaybackEngine) << "Create PlaybackEngine";
    qRegisterMetaType<QFFmpeg::Packet>();
    qRegisterMetaType<QFFmpeg::Frame>();
}
 
PlaybackEngine::~PlaybackEngine() {
    qCDebug(qLcPlaybackEngine) << "Delete PlaybackEngine";
 
    finalizeOutputs();
    forEachExistingObject([](auto &object) { object.reset(); });
    deleteFreeThreads();
}
 
void PlaybackEngine::onRendererFinished()
{
    auto isAtEnd = [this](auto trackType) {
        return !m_renderers[trackType] || m_renderers[trackType]->isAtEnd();
    };
 
    if (!isAtEnd(QPlatformMediaPlayer::VideoStream))
        return;
 
    if (!isAtEnd(QPlatformMediaPlayer::AudioStream))
        return;
 
    if (!isAtEnd(QPlatformMediaPlayer::SubtitleStream) && !hasMediaStream())
        return;
 
    if (std::exchange(m_state, QMediaPlayer::StoppedState) == QMediaPlayer::StoppedState)
        return;
 
    finilizeTime(duration());
 
    forceUpdate();
 
    qCDebug(qLcPlaybackEngine) << "Playback engine end of stream";
 
    emit endOfStream();
}
 
void PlaybackEngine::onRendererLoopChanged(quint64 id, qint64 offset, int loopIndex)
{
    if (!hasRenderer(id))
        return;
 
    if (loopIndex > m_currentLoopOffset.index) {
        m_currentLoopOffset = { offset, loopIndex };
        emit loopChanged();
    } else if (loopIndex == m_currentLoopOffset.index && offset != m_currentLoopOffset.pos) {
        qWarning() << "Unexpected offset for loop" << loopIndex << ":" << offset << "vs"
                   << m_currentLoopOffset.pos;
        m_currentLoopOffset.pos = offset;
    }
}
 
void PlaybackEngine::onRendererSynchronized(quint64 id, std::chrono::steady_clock::time_point tp,
                                            qint64 pos)
{
    if (!hasRenderer(id))
        return;
 
    Q_ASSERT(m_renderers[QPlatformMediaPlayer::AudioStream]
             && m_renderers[QPlatformMediaPlayer::AudioStream]->id() == id);
 
    if (m_timeController.positionFromTime(tp) < pos) {
        // TODO: maybe check with an asset
        qWarning() << "Unexpected synchronization " << m_timeController.positionFromTime(tp) - pos;
    }
 
    m_timeController.sync(tp, pos);
 
    forEachExistingObject<Renderer>([&](auto &renderer) {
        if (id != renderer->id())
            renderer->syncSoft(tp, pos);
    });
}
 
void PlaybackEngine::setState(QMediaPlayer::PlaybackState state) {
    if (!m_context)
        return;
 
    if (state == m_state)
        return;
 
    const auto prevState = std::exchange(m_state, state);
 
    if (m_state == QMediaPlayer::StoppedState) {
        finalizeOutputs();
        finilizeTime(0);
    }
 
    if (prevState == QMediaPlayer::StoppedState || m_state == QMediaPlayer::StoppedState)
        recreateObjects();
 
    if (prevState == QMediaPlayer::StoppedState)
        triggerStepIfNeeded();
 
    updateObjectsPausedState();
}
 
void PlaybackEngine::updateObjectsPausedState()
{
    const auto paused = m_state != QMediaPlayer::PlayingState;
    m_timeController.setPaused(paused);
 
    forEachExistingObject([&](auto &object) {
        bool objectPaused = false;
 
        if constexpr (std::is_same_v<decltype(*object), Renderer &>)
            objectPaused = paused;
        else if constexpr (shouldPauseStreams) {
            auto streamPaused = [](bool p, auto &r) {
                const auto needMoreFrames = r && r->stepInProgress();
                return p && !needMoreFrames;
            };
 
            if constexpr (std::is_same_v<decltype(*object), StreamDecoder &>)
                objectPaused = streamPaused(paused, renderer(object->trackType()));
            else
                objectPaused = std::accumulate(m_renderers.begin(), m_renderers.end(), paused,
                                               streamPaused);
        }
 
        object->setPaused(objectPaused);
    });
}
 
void PlaybackEngine::ObjectDeleter::operator()(PlaybackEngineObject *object) const
{
    Q_ASSERT(engine);
    if (!std::exchange(engine->m_threadsDirty, true))
        QMetaObject::invokeMethod(engine, &PlaybackEngine::deleteFreeThreads, Qt::QueuedConnection);
 
    object->kill();
}
 
void PlaybackEngine::registerObject(PlaybackEngineObject &object)
{
    connect(&object, &PlaybackEngineObject::error, this, &PlaybackEngine::errorOccured);
 
    auto threadName = objectThreadName(object);
    auto &thread = m_threads[threadName];
    if (!thread) {
        thread = std::make_unique<QThread>();
        thread->setObjectName(threadName);
        thread->start();
    }
 
    Q_ASSERT(object.thread() != thread.get());
    object.moveToThread(thread.get());
}
 
PlaybackEngine::RendererPtr
PlaybackEngine::createRenderer(QPlatformMediaPlayer::TrackType trackType)
{
    switch (trackType) {
    case QPlatformMediaPlayer::VideoStream:
        return m_videoSink
                ? createPlaybackEngineObject<VideoRenderer>(m_timeController, m_videoSink)
                : RendererPtr{ {}, {} };
    case QPlatformMediaPlayer::AudioStream:
        return m_audioOutput
                ? createPlaybackEngineObject<AudioRenderer>(m_timeController, m_audioOutput)
                : RendererPtr{ {}, {} };
    case QPlatformMediaPlayer::SubtitleStream:
        return m_videoSink
                ? createPlaybackEngineObject<SubtitleRenderer>(m_timeController, m_videoSink)
                : RendererPtr{ {}, {} };
    default:
        return { {}, {} };
    }
}
 
template<typename C, typename Action>
void PlaybackEngine::forEachExistingObject(Action &&action)
{
    auto handleNotNullObject = [&](auto &object) {
        if constexpr (std::is_base_of_v<C, std::remove_reference_t<decltype(*object)>>)
            if (object)
                action(object);
    };
 
    handleNotNullObject(m_demuxer);
    std::for_each(m_streams.begin(), m_streams.end(), handleNotNullObject);
    std::for_each(m_renderers.begin(), m_renderers.end(), handleNotNullObject);
}
 
template<typename Action>
void PlaybackEngine::forEachExistingObject(Action &&action)
{
    forEachExistingObject<PlaybackEngineObject>(std::forward<Action>(action));
}
 
void PlaybackEngine::seek(qint64 pos)
{
    pos = qBound(0, pos, duration());
 
    m_timeController.setPaused(true);
    m_timeController.sync(m_currentLoopOffset.pos + pos);
 
    forceUpdate();
}
 
void PlaybackEngine::setLoops(int loops)
{
    if (!isSeekable()) {
        qWarning() << "Cannot set loops for non-seekable source";
        return;
    }
 
    if (std::exchange(m_loops, loops) == loops)
        return;
 
    qCDebug(qLcPlaybackEngine) << "set playback engine loops:" << loops << "prev loops:" << m_loops
                               << "index:" << m_currentLoopOffset.index;
 
    if (m_demuxer)
        m_demuxer->setLoops(loops);
}
 
void PlaybackEngine::triggerStepIfNeeded()
{
    if (m_state != QMediaPlayer::PausedState)
        return;
 
    if (m_renderers[QPlatformMediaPlayer::VideoStream])
        m_renderers[QPlatformMediaPlayer::VideoStream]->doForceStep();
 
    // TODO: maybe trigger SubtitleStream.
    // If trigger it, we have to make seeking for the current subtitle frame more stable.
    // Or set some timeout for seeking.
}
 
QString PlaybackEngine::objectThreadName(const PlaybackEngineObject &object)
{
    QString result = object.metaObject()->className();
    if (auto stream = qobject_cast<const StreamDecoder *>(&object))
        result += QString::number(stream->trackType());
 
    return result;
}
 
void PlaybackEngine::setPlaybackRate(float rate) {
    if (rate == playbackRate())
        return;
 
    m_timeController.setPlaybackRate(rate);
    forEachExistingObject<Renderer>([rate](auto &renderer) { renderer->setPlaybackRate(rate); });
}
 
float PlaybackEngine::playbackRate() const {
    return m_timeController.playbackRate();
}
 
void PlaybackEngine::recreateObjects()
{
    m_timeController.setPaused(true);
 
    forEachExistingObject([](auto &object) { object.reset(); });
 
    createObjectsIfNeeded();
}
 
void PlaybackEngine::createObjectsIfNeeded()
{
    if (m_state == QMediaPlayer::StoppedState || !m_context)
        return;
 
    for (int i = 0; i < QPlatformMediaPlayer::NTrackTypes; ++i)
        createStreamAndRenderer(static_cast<QPlatformMediaPlayer::TrackType>(i));
 
    createDemuxer();
}
 
void PlaybackEngine::forceUpdate()
{
    recreateObjects();
    triggerStepIfNeeded();
    updateObjectsPausedState();
}
 
void PlaybackEngine::createStreamAndRenderer(QPlatformMediaPlayer::TrackType trackType)
{
    auto codec = codecForTrack(trackType);
 
    auto &renderer = m_renderers[trackType];
 
    if (!codec)
        return;
 
    if (!renderer) {
        renderer = createRenderer(trackType);
 
        if (!renderer)
            return;
 
        connect(renderer.get(), &Renderer::synchronized, this,
                &PlaybackEngine::onRendererSynchronized);
 
        connect(renderer.get(), &Renderer::loopChanged, this,
                &PlaybackEngine::onRendererLoopChanged);
 
        if constexpr (shouldPauseStreams)
            connect(renderer.get(), &Renderer::forceStepDone, this,
                    &PlaybackEngine::updateObjectsPausedState);
 
        connect(renderer.get(), &PlaybackEngineObject::atEnd, this,
                &PlaybackEngine::onRendererFinished);
    }
 
    auto &stream = m_streams[trackType] =
            createPlaybackEngineObject<StreamDecoder>(*codec, renderer->seekPosition());
 
    Q_ASSERT(trackType == stream->trackType());
 
    connect(stream.get(), &StreamDecoder::requestHandleFrame, renderer.get(), &Renderer::render);
    connect(stream.get(), &PlaybackEngineObject::atEnd, renderer.get(),
            &Renderer::onFinalFrameReceived);
    connect(renderer.get(), &Renderer::frameProcessed, stream.get(),
            &StreamDecoder::onFrameProcessed);
}
 
std::optional<Codec> PlaybackEngine::codecForTrack(QPlatformMediaPlayer::TrackType trackType)
{
    const auto streamIndex = m_currentAVStreamIndex[trackType];
    if (streamIndex < 0)
        return {};
 
    auto &result = m_codecs[trackType];
 
    if (!result) {
        qCDebug(qLcPlaybackEngine)
                << "Create codec for stream:" << streamIndex << "trackType:" << trackType;
        auto maybeCodec = Codec::create(m_context->streams[streamIndex]);
 
        if (!maybeCodec) {
            emit errorOccured(QMediaPlayer::FormatError,
                              "Cannot create codec," + maybeCodec.error());
            return {};
        }
 
        result = maybeCodec.value();
    }
 
    return result;
}
 
bool PlaybackEngine::hasMediaStream() const
{
    return m_renderers[QPlatformMediaPlayer::AudioStream]
            || m_renderers[QPlatformMediaPlayer::VideoStream];
}
 
void PlaybackEngine::createDemuxer()
{
    decltype(m_currentAVStreamIndex) streamIndexes = { -1, -1, -1 };
 
    bool hasStreams = false;
    forEachExistingObject<StreamDecoder>([&](auto &stream) {
        hasStreams = true;
        const auto trackType = stream->trackType();
        streamIndexes[trackType] = m_currentAVStreamIndex[trackType];
    });
 
    if (!hasStreams)
        return;
 
    const PositionWithOffset positionWithOffset{ currentPosition(false), m_currentLoopOffset };
 
    m_demuxer = createPlaybackEngineObject<Demuxer>(m_context.get(), positionWithOffset,
                                                    streamIndexes, m_loops);
 
    forEachExistingObject<StreamDecoder>([&](auto &stream) {
        connect(m_demuxer.get(), Demuxer::signalByTrackType(stream->trackType()), stream.get(),
                &StreamDecoder::decode);
        connect(m_demuxer.get(), &PlaybackEngineObject::atEnd, stream.get(),
                &StreamDecoder::onFinalPacketReceived);
        connect(stream.get(), &StreamDecoder::packetProcessed, m_demuxer.get(),
                &Demuxer::onPacketProcessed);
    });
}
 
void PlaybackEngine::deleteFreeThreads() {
    m_threadsDirty = false;
    auto freeThreads = std::move(m_threads);
 
    forEachExistingObject([&](auto &object) {
        m_threads.insert(freeThreads.extract(objectThreadName(*object)));
    });
 
    for (auto &[name, thr] : freeThreads)
        thr->quit();
 
    for (auto &[name, thr] : freeThreads)
        thr->wait();
}
 
bool PlaybackEngine::setMedia(const QUrl &media, QIODevice *stream)
{
    stop();
 
    m_codecs = {};
 
    if (auto error = recreateAVFormatContext(media, stream)) {
        emit errorOccured(error->code, error->description);
        return false;
    }
 
    return true;
}
 
void PlaybackEngine::setVideoSink(QVideoSink *sink)
{
    auto prev = std::exchange(m_videoSink, sink);
    if (prev == sink)
        return;
 
    updateActiveVideoOutput(sink);
 
    if (!sink || !prev) {
        // might need some improvements
        forceUpdate();
    }
}
 
void PlaybackEngine::setAudioSink(QPlatformAudioOutput *output) {
    setAudioSink(output ? output->q : nullptr);
}
 
void PlaybackEngine::setAudioSink(QAudioOutput *output)
{
    auto prev = std::exchange(m_audioOutput, output);
    if (prev == output)
        return;
 
    updateActiveAudioOutput(output);
 
    if (!output || !prev) {
        // might need some improvements
        forceUpdate();
    }
}
 
qint64 PlaybackEngine::currentPosition(bool topPos) const {
    std::optional<qint64> pos;
 
    for (size_t i = 0; i < m_renderers.size(); ++i) {
        const auto &renderer = m_renderers[i];
        if (!renderer)
            continue;
 
        // skip subtitle stream for finding lower rendering position
        if (!topPos && i == QPlatformMediaPlayer::SubtitleStream && hasMediaStream())
            continue;
 
        const auto rendererPos = renderer->lastPosition();
        pos = !pos       ? rendererPos
                : topPos ? std::max(*pos, rendererPos)
                         : std::min(*pos, rendererPos);
    }
 
    if (!pos)
        pos = m_timeController.currentPosition();
 
    return qBound(0, *pos - m_currentLoopOffset.pos, duration());
}
 
void PlaybackEngine::setActiveTrack(QPlatformMediaPlayer::TrackType trackType, int streamNumber)
{
    if (!MediaDataHolder::setActiveTrack(trackType, streamNumber))
        return;
 
    m_codecs[trackType] = {};
 
    m_renderers[trackType].reset();
    m_streams = defaultObjectsArray<decltype(m_streams)>();
    m_demuxer.reset();
 
    createObjectsIfNeeded();
    updateObjectsPausedState();
}
 
void PlaybackEngine::finilizeTime(qint64 pos)
{
    Q_ASSERT(pos >= 0 && pos <= duration());
 
    m_timeController.setPaused(true);
    m_timeController.sync(pos);
    m_currentLoopOffset = {};
}
 
void PlaybackEngine::finalizeOutputs()
{
    updateActiveAudioOutput(nullptr);
    updateActiveVideoOutput(nullptr, true);
}
 
bool PlaybackEngine::hasRenderer(quint64 id) const
{
    return std::any_of(m_renderers.begin(), m_renderers.end(),
                       [id](auto &renderer) { return renderer && renderer->id() == id; });
}
 
void PlaybackEngine::updateActiveAudioOutput(QAudioOutput *output)
{
    if (auto renderer =
                qobject_cast<AudioRenderer *>(m_renderers[QPlatformMediaPlayer::AudioStream].get()))
        renderer->setOutput(output);
}
 
void PlaybackEngine::updateActiveVideoOutput(QVideoSink *sink, bool cleanOutput)
{
    if (auto renderer = qobject_cast<SubtitleRenderer *>(
                m_renderers[QPlatformMediaPlayer::SubtitleStream].get()))
        renderer->setOutput(sink, cleanOutput);
    if (auto renderer =
                qobject_cast<VideoRenderer *>(m_renderers[QPlatformMediaPlayer::VideoStream].get()))
        renderer->setOutput(sink, cleanOutput);
}
}
 
QT_END_NAMESPACE
 
#include "moc_qffmpegplaybackengine_p.cpp"