[Development] Multimedia video playback broken in Qt 5.x for Windows WMF OpenGL version

[Ola Røer Thorsen]

Hi,

during developing an application which amongst other things plays back 
video files using the Qt 5.1 beta version on Windows 7, I've run into a 
serious problem with the media backend.

Basically if I try to play back some video file, use "Big buck bunny" 
for example from here, http://www.bigbuckbunny.org/index.php/download/ , 
take the 854x480p h264 file (or any other for that matter). Use the 
CuteTime demo player from here, https://github.com/nezticle/cutetime as 
it shows the same issue that I get in my own player.

Playback starts OK but if you let it play until 3:34, it will play in 
"fast-forward". Trying to seek before this happens will make the video 
hang. Before 3:34 there will be the occational video stutter, with this 
debug output appearing on the console:
currentPresentTime = 102.334 and sampleTime is 102.249

This only happens using the OpenGL build, not if you use the 
Angle-build. The issue always happens at about 3:34 into the film, also 
with my own video files. I have not been able to reproduce this using 
one of the example players that come with Qt, it seems like it is 
somehow triggered by having more than just a video item on the screen 
using Quick2 (such as a text label with the current media position).

If any of you could please try this out as well and confirm it's not 
just on my computer, I'll file a bug report?

I've briefly looked into the WMF backend code and found that there is 
indeed some ifdef's concerning the use of either OpenGL or Angle.

Best regards,
Ola Røer Thorsen


<https://github.com/nezticle/cutetime>
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