WMF: improve changing playback rate on a media player.

When going back to normal rate after playing in fast forward (greater
than 2x), playback seemed frozen for some amount of time (up to 8
seconds).
When playing in fast forward, only key frames are shown, ignoring all
the others. When returning to a normal rate, the source reader will
usually be pointing to a key frame in the future compared to the
player clock position, meaning that all the frames in between won't be
shown until the player clock catches up with the latest key frame that
was read.

When leaving fast-forward, we now reset the position on the player to
force the source reader to point back to the frame at the current clock
position and avoid the seamingly frozen playback.

Also, emit playbackRateChanged() signal when changing the playback
rate.

Change-Id: I4f04f0f250083378e94fb4a47f9f917abeaaf24e
Reviewed-by: Christian Stromme <christian.stromme@digia.com>

2 files changed, 48 insertions, 6 deletions

diff --git a/src/plugins/wmf/player/mfplayersession.cpp b/src/plugins/wmf/player/mfplayersession.cpp
index 69958061b..f61f7aba2 100644
--- a/src/plugins/wmf/player/mfplayersession.cpp
+++ b/src/plugins/wmf/player/mfplayersession.cpp
@@ -1157,8 +1157,8 @@ void MFPlayerSession::setPositionInternal(qint64 position, Command requestCmd)
 
 qreal MFPlayerSession::playbackRate() const
 {
-    if (m_pendingState != NoPending)
-        return m_request.rate;
+    if (m_scrubbing)
+        return m_restoreRate;
     return m_state.rate;
 }
 
@@ -1166,6 +1166,7 @@ void MFPlayerSession::setPlaybackRate(qreal rate)
 {
     if (m_scrubbing) {
         m_restoreRate = rate;
+        emit playbackRateChanged(rate);
         return;
     }
     setPlaybackRateInternal(rate);
@@ -1194,6 +1195,8 @@ void MFPlayerSession::setPlaybackRateInternal(qreal rate)
         isThin = TRUE;
         if (FAILED(m_rateSupport->IsRateSupported(isThin, rate, NULL))) {
             qWarning() << "unable to set playbackrate = " << rate;
+            m_pendingRate = m_request.rate = m_state.rate;
+            return;
         }
     }
     if (m_pendingState != NoPending) {
@@ -1219,6 +1222,7 @@ void MFPlayerSession::commitRateChange(qreal rate, BOOL isThin)
     MFTIME  hnsSystemTime = 0;
     MFTIME  hnsClockTime = 0;
     Command cmdNow = m_state.command;
+    bool resetPosition = false;
     // Allowed rate transitions:
     // Positive <-> negative:   Stopped
     // Negative <-> zero:       Stopped
@@ -1229,7 +1233,12 @@ void MFPlayerSession::commitRateChange(qreal rate, BOOL isThin)
             m_presentationClock->GetCorrelatedTime(0, &hnsClockTime, &hnsSystemTime);
             Q_ASSERT(hnsSystemTime != 0);
 
-            m_request.setCommand(rate < 0 || m_state.rate < 0 ? CmdSeekResume : CmdStart);
+            if (rate < 0 || m_state.rate < 0)
+                m_request.setCommand(CmdSeekResume);
+            else if (isThin || m_state.isThin)
+                m_request.setCommand(CmdStartAndSeek);
+            else
+                m_request.setCommand(CmdStart);
 
             // We need to stop only when dealing with negative rates
             if (rate >= 0 && m_state.rate >= 0)
@@ -1247,7 +1256,9 @@ void MFPlayerSession::commitRateChange(qreal rate, BOOL isThin)
                 // session cannot transition back from stopped to paused.
                 // Therefore, this rate transition is not supported while paused.
                 qWarning() << "Unable to change rate from positive to negative or vice versa in paused state";
-                return;
+                rate = m_state.rate;
+                isThin = m_state.isThin;
+                goto done;
             }
 
             // This happens when resuming playback after scrubbing in pause mode.
@@ -1279,17 +1290,42 @@ void MFPlayerSession::commitRateChange(qreal rate, BOOL isThin)
 
         // Resume to the current position (stop() will reset the position to 0)
         m_request.start = hnsClockTime / 10000;
+    } else if (!isThin && m_state.isThin) {
+        if (cmdNow == CmdStart) {
+            // When thinning, only key frames are read and presented. Going back
+            // to normal playback requires to reset the current position to force
+            // the pipeline to decode the actual frame at the current position
+            // (which might be earlier than the last decoded key frame)
+            resetPosition = true;
+        } else if (cmdNow == CmdPause) {
+            // If paused, dont reset the position until we resume, otherwise
+            // a new frame will be rendered
+            m_presentationClock->GetCorrelatedTime(0, &hnsClockTime, &hnsSystemTime);
+            m_request.setCommand(CmdSeekResume);
+            m_request.start = hnsClockTime / 10000;
+        }
+
     }
 
     // Set the rate.
     if (FAILED(m_rateControl->SetRate(isThin, rate))) {
         qWarning() << "failed to set playbackrate = " << rate;
-        return;
+        rate = m_state.rate;
+        isThin = m_state.isThin;
+        goto done;
     }
 
+    if (resetPosition) {
+        m_presentationClock->GetCorrelatedTime(0, &hnsClockTime, &hnsSystemTime);
+        setPosition(hnsClockTime / 10000);
+    }
+
+done:
     // Adjust our current rate and requested rate.
     m_pendingRate = m_request.rate = m_state.rate = rate;
-
+    if (rate != 0)
+        m_state.isThin = isThin;
+    emit playbackRateChanged(rate);
 }
 
 void MFPlayerSession::scrub(bool enableScrub)
@@ -1705,6 +1741,11 @@ void MFPlayerSession::updatePendingCommands(Command command)
         case CmdSeek:
         case CmdSeekResume:
             setPositionInternal(m_request.start, m_request.command);
+            break;
+        case CmdStartAndSeek:
+            start();
+            setPositionInternal(m_request.start, m_request.command);
+            break;
         }
         m_request.setCommand(CmdNone);
     }
diff --git a/src/plugins/wmf/player/mfplayersession.h b/src/plugins/wmf/player/mfplayersession.h
index 3ba43ce58..2c87f3cc6 100644
--- a/src/plugins/wmf/player/mfplayersession.h
+++ b/src/plugins/wmf/player/mfplayersession.h
@@ -165,6 +165,7 @@ private:
         CmdPause,
         CmdSeek,
         CmdSeekResume,
+        CmdStartAndSeek
     };
 
     void clear();