qffmpegplaybackengine_p.h

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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
#ifndef QFFMPEGPLAYBACKENGINE_P_H
#define QFFMPEGPLAYBACKENGINE_P_H
 
//
//  W A R N I N G
//  -------------
//
// This file is not part of the Qt API. It exists purely as an
// implementation detail. This header file may change from version to
// version without notice, or even be removed.
//
// We mean it.
//
 
/* Playback engine design description.
 *
 *
 * PLAYBACK ENGINE OBJECTS
 *
 * - Playback engine manages 7 objects inside, each one works in a separate thread.
 * Each object inherits PlaybackEngineObject. The objects are:
 *    Demuxer
 *    Stream Decoders: audio, video, subtitles
 *    Renderers: audio, video, subtitles
 *
 *
 * THREADS:
 *
 * - By default, each object works in a separate thread. It's easy to reconfigure
 *   to using several objects in thread.
 * - New thread is allocated if a new object is created and the engine doesn't
 *   have free threads. If it does, the thread is to be reused.
 * - If all objects for some thread are deleted, the thread becomes free and the engine
 *   postpones its termination.
 *
 * OBJECTS WEAK CONNECTIVITY
 *
 * - The objects know nothing about others and about PlaybackEngine.
 *   For any interractions the objects use slots/signals.
 *
 * - PlaybackEngine knows the objects object and is able to create/delete them and
 *   call their public methods.
 *
 */
 
#include "playbackengine/qffmpegplaybackenginedefs_p.h"
#include "playbackengine/qffmpegtimecontroller_p.h"
#include "playbackengine/qffmpegmediadataholder_p.h"
#include "playbackengine/qffmpegcodec_p.h"
#include "playbackengine/qffmpegpositionwithoffset_p.h"
 
#include <unordered_map>
 
QT_BEGIN_NAMESPACE
 
class QAudioSink;
class QVideoSink;
class QAudioOutput;
class QFFmpegMediaPlayer;
 
namespace QFFmpeg
{
 
class PlaybackEngine : public QObject, public MediaDataHolder
{
    Q_OBJECT
public:
    PlaybackEngine();
 
    ~PlaybackEngine() override;
 
    bool setMedia(const QUrl &media, QIODevice *stream);
 
    void setVideoSink(QVideoSink *sink);
 
    void setAudioSink(QAudioOutput *output);
 
    void setAudioSink(QPlatformAudioOutput *output);
 
    void setState(QMediaPlayer::PlaybackState state);
 
    void play() {
        setState(QMediaPlayer::PlayingState);
    }
    void pause() {
        setState(QMediaPlayer::PausedState);
    }
    void stop() {
        setState(QMediaPlayer::StoppedState);
    }
 
    void seek(qint64 pos);
 
    void setLoops(int loopsCount);
 
    void setPlaybackRate(float rate);
 
    float playbackRate() const;
 
    void setActiveTrack(QPlatformMediaPlayer::TrackType type, int streamNumber);
 
    using MediaDataHolder::activeTrack;
 
    qint64 currentPosition(bool topPos = true) const;
 
signals:
    void endOfStream();
    void errorOccured(int, const QString &);
    void loopChanged();
 
protected: // objects managing
    struct ObjectDeleter
    {
        void operator()(PlaybackEngineObject *) const;
 
        PlaybackEngine *engine = nullptr;
    };
 
    template<typename T>
    using ObjectPtr = std::unique_ptr<T, ObjectDeleter>;
 
    using RendererPtr = ObjectPtr<Renderer>;
    using StreamPtr = ObjectPtr<StreamDecoder>;
 
    template<typename T, typename... Args>
    ObjectPtr<T> createPlaybackEngineObject(Args &&...args);
 
    virtual RendererPtr createRenderer(QPlatformMediaPlayer::TrackType trackType);
 
    void updateActiveAudioOutput(QAudioOutput *output);
 
    void updateActiveVideoOutput(QVideoSink *sink, bool cleanOutput = false);
 
private:
    void createStreamAndRenderer(QPlatformMediaPlayer::TrackType trackType);
 
    void createDemuxer();
 
    void registerObject(PlaybackEngineObject &object);
 
    template<typename C, typename Action>
    void forEachExistingObject(Action &&action);
 
    template<typename Action>
    void forEachExistingObject(Action &&action);
 
    void forceUpdate();
 
    void recreateObjects();
 
    void createObjectsIfNeeded();
 
    void updateObjectsPausedState();
 
    void deleteFreeThreads();
 
    void onRendererSynchronized(quint64 id, std::chrono::steady_clock::time_point time,
                                qint64 trackTime);
 
    void onRendererFinished();
 
    void onRendererLoopChanged(quint64 id, qint64 offset, int loopIndex);
 
    void triggerStepIfNeeded();
 
    static QString objectThreadName(const PlaybackEngineObject &object);
 
    std::optional<Codec> codecForTrack(QPlatformMediaPlayer::TrackType trackType);
 
    bool hasMediaStream() const;
 
    void finilizeTime(qint64 pos);
 
    void finalizeOutputs();
 
    bool hasRenderer(quint64 id) const;
 
private:
    TimeController m_timeController;
 
    std::unordered_map<QString, std::unique_ptr<QThread>> m_threads;
    bool m_threadsDirty = false;
 
    QPointer<QVideoSink> m_videoSink;
    QPointer<QAudioOutput> m_audioOutput;
 
    QMediaPlayer::PlaybackState m_state = QMediaPlayer::StoppedState;
 
    ObjectPtr<Demuxer> m_demuxer;
    std::array<StreamPtr, QPlatformMediaPlayer::NTrackTypes> m_streams;
    std::array<RendererPtr, QPlatformMediaPlayer::NTrackTypes> m_renderers;
 
    std::array<std::optional<Codec>, QPlatformMediaPlayer::NTrackTypes> m_codecs;
    int m_loops = QMediaPlayer::Once;
    LoopOffset m_currentLoopOffset;
};
 
template<typename T, typename... Args>
PlaybackEngine::ObjectPtr<T> PlaybackEngine::createPlaybackEngineObject(Args &&...args)
{
    auto result = ObjectPtr<T>(new T(std::forward<Args>(args)...), { this });
    registerObject(*result);
    return result;
}
}
 
QT_END_NAMESPACE
 
#endif // QFFMPEGPLAYBACKENGINE_P_H