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>

2 files changed, 46 insertions, 56 deletions

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;