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

Ola Røer Thorsen ola at silentwings.no
Mon Jun 17 14:04:16 CEST 2013

thanks for the feedback! I have a Asus G74S laptop with nvidia a 560M 
GPU. I've created a bug report here:

thanks for the information. I'll try to use Angle instead for now, but 
this will become an issue once we need to use more advanced OpenGL 
features. I use Qt to overlay data on top of a 3D viewer application.

For the moment, the other issue I found last week is more important and 
is valid for both the Angle and OpenGL versions,

While discussing this, I also found that using the Angle-version on 
"cheaper" Windows 7 laptops with Intel GPUs, the video is just black. 
There is no apparent error messages. The video appears to be playing, 
but the actual texture is completely black. Same video plays back fine 
in Windows Media Player on the same machines. This is partially why I 
wanted to try the OpenGL-version to see if that was any better. Is this 
also a known issue, or should I create an issue on the tracker for this 
as well?

Best regards,
Ola Røer Thorsen

Den 2013-06-17 13:40, skrev Lopes Yoann:
> Hi,
> This is a known issue.
> Angle and OpenGL builds use different decoding pipelines. With Angle, 
> the plugin can do hardware decoding using DXVA, while when using pure 
> OpenGL it is not possible and the pipeline is setup with a custom 
> video sink (software decoding) that is known to be buggy...
> If you can, use the Angle build. Not only you'll get better 
> performance but it will also be much more stable.
> The problem you are reporting should probably be fixed anyway, please 
> create a bug report.
> Yoann Lopes
> Senior Software Engineer - Digia, Qt
> Visit us on: http://qt.digia.com
> On Jun 17, 2013, at 1:18 PM, Mitch Curtis wrote:
>> On 06/17/2013 08:36 AM, Ola Røer Thorsen wrote:
>>> 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/ 
>>> <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 
>>> <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>
>>> _______________________________________________
>>> Development mailing list
>>> Development at qt-project.org <mailto:Development at qt-project.org>
>>> http://lists.qt-project.org/mailman/listinfo/development
>> Hi Ola.
>> I can confirm this with the latest SDK beta on Windows 7 64-bit, so
>> please create a bug report. Which video card do you have?
>> _______________________________________________
>> Development mailing list
>> Development at qt-project.org <mailto:Development at qt-project.org>
>> http://lists.qt-project.org/mailman/listinfo/development

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