QMediaPlayer 'play' jumps to wrong position after seek

Summary

As per attached code, using QMediaPlayer and (in my case) QVideoWidget:

• Start app and video autoplays
• Pause at e.g. 3s
• setPosition(0.5s)
• Play

EXPECTED: Video plays from setPosition location i.e. 0.5s

ACTUAL: Video plays from pause position i.e. 3s - visually it jerks forward.

Further Details from MFPlayerSession.cpp

When a IMFMediaSession pause() completes, the callback MFPlayerSession::handleSessionEvent caches the current WMF clock time as m_position:

case MESessionPaused:        
    m_position = position() * 10000;

Clearly, this would allow a consecutive start() to resume at m_position which makes sense.

If instead, setPosition() is called after pause(), a slightly different situation arises. setPositionInternal() calls setScrub(true) which correctly sets the frame rate to 0 and flags a scrub as taking place (m_scrubbing=true).

However, when start() is called the following happens (elided):

if (m_scrubbing)
            scrub(false);
  //...elided     
PROPVARIANT varStart;        
InitPropVariantFromInt64(m_position, &varStart);
if (SUCCEEDED(m_session->Start(&GUID_NULL, &varStart))) { 
//...}

 
Thus start() always resumes from the cached m_position.

Perhaps, after turning off scrubbing state, start() could somehow adjust the cached m_position to the seek location:

if (m_scrubbing) {
    set m_position to current seek position. Possibly using 'm_state.start'?
    scrub(false)
}
  //...elided     
PROPVARIANT varStart;        
InitPropVariantFromInt64(m_position, &varStart);
if (SUCCEEDED(m_session->Start(&GUID_NULL, &varStart))) { 
//...}

Then it would resume playback from wherever the seek ended.