Ensure pre-roll frames are displayed when gstreamer backend is paused.

Perform a seek before transitioning from the stopped state to paused or
playing to force the pipeline to resupply the video sink with any
pre-roll buffer it may have previously ignored during loading.  And
don't assume showPrerollFrames to be true if the current state is not
stopped as the policy handling may have prevented an effectual state
change.

Change-Id: I288a70bc4da32f3534eab4b14702ca8f8fdb4222
Reviewed-by: Yoann Lopes <yoann.lopes@digia.com>

4 files changed, 51 insertions, 150 deletions

diff --git a/src/gsttools/qvideosurfacegstsink.cpp b/src/gsttools/qvideosurfacegstsink.cpp
index 36f8c049b..f3e2d884c 100644
--- a/src/gsttools/qvideosurfacegstsink.cpp
+++ b/src/gsttools/qvideosurfacegstsink.cpp
@@ -56,7 +56,6 @@ QVideoSurfaceGstDelegate::QVideoSurfaceGstDelegate(
     : m_surface(surface)
     , m_pool(0)
     , m_renderReturn(GST_FLOW_ERROR)
-    , m_lastPrerolledBuffer(0)
     , m_bytesPerLine(0)
     , m_startCanceled(false)
 {
@@ -74,7 +73,6 @@ QVideoSurfaceGstDelegate::QVideoSurfaceGstDelegate(
 
 QVideoSurfaceGstDelegate::~QVideoSurfaceGstDelegate()
 {
-    setLastPrerolledBuffer(0);
 }
 
 QList<QVideoFrame::PixelFormat> QVideoSurfaceGstDelegate::supportedPixelFormats(QAbstractVideoBuffer::HandleType handleType) const
@@ -209,23 +207,6 @@ GstFlowReturn QVideoSurfaceGstDelegate::render(GstBuffer *buffer)
     return m_renderReturn;
 }
 
-void QVideoSurfaceGstDelegate::setLastPrerolledBuffer(GstBuffer *prerolledBuffer)
-{
-    // discard previously stored buffer
-    if (m_lastPrerolledBuffer) {
-        gst_buffer_unref(m_lastPrerolledBuffer);
-        m_lastPrerolledBuffer = 0;
-    }
-
-    if (!prerolledBuffer)
-        return;
-
-    // store a reference to the buffer
-    Q_ASSERT(!m_lastPrerolledBuffer);
-    m_lastPrerolledBuffer = prerolledBuffer;
-    gst_buffer_ref(m_lastPrerolledBuffer);
-}
-
 void QVideoSurfaceGstDelegate::queuedStart()
 {
     if (!m_startCanceled) {
@@ -397,8 +378,6 @@ QVideoSurfaceGstSink *QVideoSurfaceGstSink::createSink(QAbstractVideoSurface *su
 
     sink->delegate = new QVideoSurfaceGstDelegate(surface);
 
-    g_signal_connect(G_OBJECT(sink), "notify::show-preroll-frame", G_CALLBACK(handleShowPrerollChange), sink);
-
     return sink;
 }
 
@@ -434,16 +413,15 @@ void QVideoSurfaceGstSink::class_init(gpointer g_class, gpointer class_data)
 
     sink_parent_class = reinterpret_cast<GstVideoSinkClass *>(g_type_class_peek_parent(g_class));
 
+    GstVideoSinkClass *video_sink_class = reinterpret_cast<GstVideoSinkClass *>(g_class);
+    video_sink_class->show_frame = QVideoSurfaceGstSink::show_frame;
+
     GstBaseSinkClass *base_sink_class = reinterpret_cast<GstBaseSinkClass *>(g_class);
     base_sink_class->get_caps = QVideoSurfaceGstSink::get_caps;
     base_sink_class->set_caps = QVideoSurfaceGstSink::set_caps;
     base_sink_class->buffer_alloc = QVideoSurfaceGstSink::buffer_alloc;
     base_sink_class->start = QVideoSurfaceGstSink::start;
     base_sink_class->stop = QVideoSurfaceGstSink::stop;
-    // base_sink_class->unlock = QVideoSurfaceGstSink::unlock; // Not implemented.
-    base_sink_class->event = QVideoSurfaceGstSink::event;
-    base_sink_class->preroll = QVideoSurfaceGstSink::preroll;
-    base_sink_class->render = QVideoSurfaceGstSink::render;
 
     GstElementClass *element_class = reinterpret_cast<GstElementClass *>(g_class);
     element_class->change_state = QVideoSurfaceGstSink::change_state;
@@ -709,27 +687,6 @@ void QVideoSurfaceGstSink::setFrameTimeStamps(QVideoFrame *frame, GstBuffer *buf
     }
 }
 
-void QVideoSurfaceGstSink::handleShowPrerollChange(GObject *o, GParamSpec *p, gpointer d)
-{
-    Q_UNUSED(o);
-    Q_UNUSED(p);
-    QVideoSurfaceGstSink *sink = reinterpret_cast<QVideoSurfaceGstSink *>(d);
-
-    gboolean value = true; // "show-preroll-frame" property is true by default
-    g_object_get(G_OBJECT(sink), "show-preroll-frame", &value, NULL);
-
-    GstBuffer *buffer = sink->delegate->lastPrerolledBuffer();
-    // Render the stored prerolled buffer if requested.
-    // e.g. player is in stopped mode, then seek operation is requested,
-    // surface now stores a prerolled frame, but doesn't display it until
-    // "show-preroll-frame" property is set to "true"
-    // when switching to pause or playing state.
-    if (value && buffer) {
-        sink->delegate->render(buffer);
-        sink->delegate->setLastPrerolledBuffer(0);
-    }
-}
-
 GstFlowReturn QVideoSurfaceGstSink::buffer_alloc(
         GstBaseSink *base, guint64 offset, guint size, GstCaps *caps, GstBuffer **buffer)
 {
@@ -842,44 +799,9 @@ gboolean QVideoSurfaceGstSink::stop(GstBaseSink *base)
     return TRUE;
 }
 
-gboolean QVideoSurfaceGstSink::unlock(GstBaseSink *base)
-{
-    Q_UNUSED(base);
-
-    return TRUE;
-}
-
-gboolean QVideoSurfaceGstSink::event(GstBaseSink *base, GstEvent *event)
-{
-    // discard prerolled frame
-    if (event->type == GST_EVENT_FLUSH_START) {
-        VO_SINK(base);
-        sink->delegate->setLastPrerolledBuffer(0);
-    }
-
-    return TRUE;
-}
-
-GstFlowReturn QVideoSurfaceGstSink::preroll(GstBaseSink *base, GstBuffer *buffer)
-{
-    VO_SINK(base);
-
-    gboolean value = true; // "show-preroll-frame" property is true by default
-    g_object_get(G_OBJECT(base), "show-preroll-frame", &value, NULL);
-    if (value) {
-        sink->delegate->setLastPrerolledBuffer(0); // discard prerolled buffer
-        return sink->delegate->render(buffer); // display frame
-    }
-
-    // otherwise keep a reference to the buffer to display it later
-    sink->delegate->setLastPrerolledBuffer(buffer);
-    return GST_FLOW_OK;
-}
-
-GstFlowReturn QVideoSurfaceGstSink::render(GstBaseSink *base, GstBuffer *buffer)
+GstFlowReturn QVideoSurfaceGstSink::show_frame(GstVideoSink *base, GstBuffer *buffer)
 {
     VO_SINK(base);
-    sink->delegate->setLastPrerolledBuffer(0); // discard prerolled buffer
     return sink->delegate->render(buffer);
 }
 
diff --git a/src/multimedia/gsttools_headers/qvideosurfacegstsink_p.h b/src/multimedia/gsttools_headers/qvideosurfacegstsink_p.h
index d152e2a44..11b305d27 100644
--- a/src/multimedia/gsttools_headers/qvideosurfacegstsink_p.h
+++ b/src/multimedia/gsttools_headers/qvideosurfacegstsink_p.h
@@ -84,9 +84,6 @@ public:
 
     GstFlowReturn render(GstBuffer *buffer);
 
-    GstBuffer *lastPrerolledBuffer() const { return m_lastPrerolledBuffer; }
-    void setLastPrerolledBuffer(GstBuffer *lastPrerolledBuffer); // set prerolledBuffer to 0 to discard prerolled buffer
-
 private slots:
     void queuedStart();
     void queuedStop();
@@ -108,8 +105,6 @@ private:
     QVideoSurfaceFormat m_format;
     QVideoFrame m_frame;
     GstFlowReturn m_renderReturn;
-    // this pointer is not 0 when there is a prerolled buffer waiting to be displayed
-    GstBuffer *m_lastPrerolledBuffer;
     int m_bytesPerLine;
     bool m_started;
     bool m_startCanceled;
@@ -126,8 +121,6 @@ public:
                                              QAbstractVideoBuffer::HandleType handleType = QAbstractVideoBuffer::NoHandle);
     static void setFrameTimeStamps(QVideoFrame *frame, GstBuffer *buffer);
 
-    static void handleShowPrerollChange(GObject *o, GParamSpec *p, gpointer d);
-
 private:
     static GType get_type();
     static void class_init(gpointer g_class, gpointer class_data);
@@ -147,11 +140,7 @@ private:
     static gboolean start(GstBaseSink *sink);
     static gboolean stop(GstBaseSink *sink);
 
-    static gboolean unlock(GstBaseSink *sink);
-
-    static gboolean event(GstBaseSink *sink, GstEvent *event);
-    static GstFlowReturn preroll(GstBaseSink *sink, GstBuffer *buffer);
-    static GstFlowReturn render(GstBaseSink *sink, GstBuffer *buffer);
+    static GstFlowReturn show_frame(GstVideoSink *sink, GstBuffer *buffer);
 
 private:
     QVideoSurfaceGstDelegate *delegate;
diff --git a/src/plugins/gstreamer/mediaplayer/qgstreamerplayercontrol.cpp b/src/plugins/gstreamer/mediaplayer/qgstreamerplayercontrol.cpp
index 2f7047f97..fed756ac9 100644
--- a/src/plugins/gstreamer/mediaplayer/qgstreamerplayercontrol.cpp
+++ b/src/plugins/gstreamer/mediaplayer/qgstreamerplayercontrol.cpp
@@ -60,7 +60,6 @@ QGstreamerPlayerControl::QGstreamerPlayerControl(QGstreamerPlayerSession *sessio
     , m_currentState(QMediaPlayer::StoppedState)
     , m_mediaStatus(QMediaPlayer::NoMedia)
     , m_bufferProgress(-1)
-    , m_seekToStartPending(false)
     , m_pendingSeekPosition(-1)
     , m_setMediaPending(false)
     , m_stream(0)
@@ -69,7 +68,7 @@ QGstreamerPlayerControl::QGstreamerPlayerControl(QGstreamerPlayerSession *sessio
     Q_ASSERT(m_resources);
 
     connect(m_session, SIGNAL(positionChanged(qint64)),
-            this, SLOT(updatePosition(qint64)));
+            this, SIGNAL(positionChanged(qint64)));
     connect(m_session, SIGNAL(durationChanged(qint64)),
             this, SIGNAL(durationChanged(qint64)));
     connect(m_session, SIGNAL(mutedStateChanged(bool)),
@@ -94,8 +93,6 @@ QGstreamerPlayerControl::QGstreamerPlayerControl(QGstreamerPlayerSession *sessio
             this, SLOT(handleInvalidMedia()));
     connect(m_session, SIGNAL(playbackRateChanged(qreal)),
             this, SIGNAL(playbackRateChanged(qreal)));
-    connect(m_session, SIGNAL(seekableChanged(bool)),
-            this, SLOT(applyPendingSeek(bool)));
 
     connect(m_resources, SIGNAL(resourcesGranted()), SLOT(handleResourcesGranted()));
     //denied signal should be queued to have correct state update process,
@@ -117,7 +114,7 @@ QMediaPlayerResourceSetInterface* QGstreamerPlayerControl::resources() const
 
 qint64 QGstreamerPlayerControl::position() const
 {
-    return m_seekToStartPending ? 0 : m_session->position();
+    return m_pendingSeekPosition != -1 ? m_pendingSeekPosition : m_session->position();
 }
 
 qint64 QGstreamerPlayerControl::duration() const
@@ -183,15 +180,21 @@ void QGstreamerPlayerControl::setPosition(qint64 pos)
 
     if (m_mediaStatus == QMediaPlayer::EndOfMedia) {
         m_mediaStatus = QMediaPlayer::LoadedMedia;
-        m_seekToStartPending = true;
     }
 
-    if (m_session->isSeekable() && m_session->seek(pos)) {
-        m_seekToStartPending = false;
-    } else {
+    if (m_currentState == QMediaPlayer::StoppedState) {
         m_pendingSeekPosition = pos;
-        //don't display the first video frame since it's not what user requested.
-        m_session->showPrerollFrames(false);
+        emit positionChanged(m_pendingSeekPosition);
+    } else if (m_session->isSeekable()) {
+        m_session->showPrerollFrames(true);
+        m_session->seek(pos);
+        m_pendingSeekPosition = -1;
+    } else if (m_session->state() == QMediaPlayer::StoppedState) {
+        m_pendingSeekPosition = pos;
+        emit positionChanged(m_pendingSeekPosition);
+    } else if (m_pendingSeekPosition != -1) {
+        m_pendingSeekPosition = -1;
+        emit positionChanged(m_pendingSeekPosition);
     }
 
     popAndNotifyState();
@@ -239,26 +242,30 @@ void QGstreamerPlayerControl::playOrPause(QMediaPlayer::State newState)
     }
 #endif
 
+    if (m_mediaStatus == QMediaPlayer::EndOfMedia && m_pendingSeekPosition == -1) {
+        m_pendingSeekPosition = 0;
+    }
+
     if (!m_resources->isGranted())
         m_resources->acquire();
 
     if (m_resources->isGranted()) {
-        if (m_seekToStartPending) {
+        // show prerolled frame if switching from stopped state
+        if (m_pendingSeekPosition == -1) {
+            m_session->showPrerollFrames(true);
+        } else if (m_session->state() == QMediaPlayer::StoppedState) {
+            // Don't evaluate the next two conditions.
+        } else if (m_session->isSeekable()) {
             m_session->pause();
-            if (!m_session->seek(0)) {
-                m_bufferProgress = -1;
-                m_session->stop();
-                m_mediaStatus = QMediaPlayer::LoadingMedia;
-            }
-            m_seekToStartPending = false;
+            m_session->showPrerollFrames(true);
+            m_session->seek(m_pendingSeekPosition);
+            m_pendingSeekPosition = -1;
+        } else {
+            m_pendingSeekPosition = -1;
         }
 
         bool ok = false;
 
-        // show prerolled frame if switching from stopped state
-        if (newState != QMediaPlayer::StoppedState && m_currentState == QMediaPlayer::StoppedState && m_pendingSeekPosition == -1)
-            m_session->showPrerollFrames(true);
-
         //To prevent displaying the first video frame when playback is resumed
         //the pipeline is paused instead of playing, seeked to requested position,
         //and after seeking is finished (position updated) playback is restarted
@@ -305,7 +312,7 @@ void QGstreamerPlayerControl::stop()
             m_session->pause();
 
         if (m_mediaStatus != QMediaPlayer::EndOfMedia) {
-            m_seekToStartPending = true;
+            m_pendingSeekPosition = 0;
             emit positionChanged(position());
         }
     }
@@ -343,7 +350,7 @@ void QGstreamerPlayerControl::setMedia(const QMediaContent &content, QIODevice *
 
     m_currentState = QMediaPlayer::StoppedState;
     QMediaContent oldMedia = m_currentResource;
-    m_pendingSeekPosition = -1;
+    m_pendingSeekPosition = 0;
     m_session->showPrerollFrames(false); // do not show prerolled frames until pause() or play() explicitly called
     m_setMediaPending = false;
 
@@ -390,7 +397,6 @@ void QGstreamerPlayerControl::setMedia(const QMediaContent &content, QIODevice *
 
     m_currentResource = content;
     m_stream = stream;
-    m_seekToStartPending = false;
 
     QNetworkRequest request;
 
@@ -462,8 +468,21 @@ void QGstreamerPlayerControl::updateSessionState(QMediaPlayer::State state)
 {
     pushState();
 
-    if (state == QMediaPlayer::StoppedState)
+    if (state == QMediaPlayer::StoppedState) {
+        m_session->showPrerollFrames(false);
         m_currentState = QMediaPlayer::StoppedState;
+    }
+
+    if (state == QMediaPlayer::PausedState && m_currentState != QMediaPlayer::StoppedState) {
+        if (m_pendingSeekPosition != -1 && m_session->isSeekable()) {
+            m_session->showPrerollFrames(true);
+            m_session->seek(m_pendingSeekPosition);
+        }
+        m_pendingSeekPosition = -1;
+
+        if (m_currentState == QMediaPlayer::PlayingState)
+            m_session->play();
+    }
 
     updateMediaStatus();
 
@@ -512,7 +531,6 @@ void QGstreamerPlayerControl::processEOS()
     m_mediaStatus = QMediaPlayer::EndOfMedia;
     emit positionChanged(position());
     m_session->endOfMediaReset();
-    m_setMediaPending = true;
 
     if (m_currentState != QMediaPlayer::StoppedState) {
         m_currentState = QMediaPlayer::StoppedState;
@@ -549,17 +567,12 @@ void QGstreamerPlayerControl::setBufferProgress(int progress)
     emit bufferStatusChanged(m_bufferProgress);
 }
 
-void QGstreamerPlayerControl::applyPendingSeek(bool isSeekable)
-{
-    if (isSeekable && m_pendingSeekPosition != -1)
-        setPosition(m_pendingSeekPosition);
-}
-
 void QGstreamerPlayerControl::handleInvalidMedia()
 {
     pushState();
     m_mediaStatus = QMediaPlayer::InvalidMedia;
     m_currentState = QMediaPlayer::StoppedState;
+    m_setMediaPending = true;
     popAndNotifyState();
 }
 
@@ -636,24 +649,4 @@ void QGstreamerPlayerControl::popAndNotifyState()
     }
 }
 
-void QGstreamerPlayerControl::updatePosition(qint64 pos)
-{
-#ifdef DEBUG_PLAYBIN
-    qDebug() << Q_FUNC_INFO << pos/1000.0 << "pending:" << m_pendingSeekPosition/1000.0;
-#endif
-
-    if (m_pendingSeekPosition != -1) {
-        //seek request is complete, it's safe to resume playback
-        //with prerolled frame displayed
-        m_pendingSeekPosition = -1;
-        if (m_currentState != QMediaPlayer::StoppedState)
-            m_session->showPrerollFrames(true);
-        if (m_currentState == QMediaPlayer::PlayingState) {
-            m_session->play();
-        }
-    }
-
-    emit positionChanged(pos);
-}
-
 QT_END_NAMESPACE
diff --git a/src/plugins/gstreamer/mediaplayer/qgstreamerplayercontrol.h b/src/plugins/gstreamer/mediaplayer/qgstreamerplayercontrol.h
index 94f7b7019..0a5f8af83 100644
--- a/src/plugins/gstreamer/mediaplayer/qgstreamerplayercontrol.h
+++ b/src/plugins/gstreamer/mediaplayer/qgstreamerplayercontrol.h
@@ -103,8 +103,6 @@ private Q_SLOTS:
     void updateMediaStatus();
     void processEOS();
     void setBufferProgress(int progress);
-    void applyPendingSeek(bool isSeekable);
-    void updatePosition(qint64 pos);
 
     void handleInvalidMedia();
 
@@ -127,7 +125,6 @@ private:
     QStack<QMediaPlayer::MediaStatus> m_mediaStatusStack;
 
     int m_bufferProgress;
-    bool m_seekToStartPending;
     qint64 m_pendingSeekPosition;
     bool m_setMediaPending;
     QMediaContent m_currentResource;