[Development] QT through DirectFB on Video playback

Mandeep Sandhu mandeepsandhu.chd at gmail.com
Sun Mar 23 12:42:54 CET 2014

> So, as per your explanation, what I understand is, QT widgets can be
> rendered as is on Video , just that the widgets we create should be
> transparent.


> Please correct me if I am wrong. Ours would be a single process application.
> Video playback and QT widget would be invoked through the same app.


> I will try out the same . But, as far as I know, we will have to use
> qdirectfbscreen class provided by QT inorder have QT apps on Video playback.

I don't think so. Whatever libraries that your vendor has given you
for media playback can be used by your Qt application to initiate
media playback. Most probably you will have API's in the library to
tell the h/w which video plane you want to render the frames to. Then
it will simply be a matter of making the OSD plane transparent for
viewing the video.

> Anyways, if you have any such sample app(very minimal one) available, please
> can you share with us.

I'm afraid an example will be specific to your h/w so I won't be able
to provide one. But I'm guessing there'll be some sample app for
playback of video. You can integrate it into a simple Qt app that has
a main widget which has a portion of it's background as transparent.
All this can be done in a single process.


> Thanks and Regards,
> Poornima
> On Thu, Mar 20, 2014 at 11:17 PM, Mandeep Sandhu
> <mandeepsandhu.chd at gmail.com> wrote:
>> An embedded video SoC based DFB setup will be something like this
>> (might vary a little for your specific board):
>> a) 1 background plane (typically lowest z order)
>> b) 1 or more video planes
>> c) 1 or more OSD planes
>> b and c z-order might be interchangeable via DFB.
>> Qt typically would run on either the primary or secondary OSD planes
>> (check your vendor docs for which plane it actually uses). Any video
>> playback would typically render frames on one of the video planes.
>> In order to run Qt UI and video together you would just need to make
>> the relevant area of the Qt application transparent. The h/w will
>> blend the video and OSD planes together and show it on the video port.
>> See the widget attributes (Qt::WidgetAttribute) for the exact
>> attribute to set (I think it was WA_NoSystemBackground).
>> HTH,
>> -mandeep
>> On Thu, Mar 20, 2014 at 6:52 PM, Poornima Belavanaki
>> <poori14apr at gmail.com> wrote:
>> > Hi ,
>> >
>> > We are developing Qt apps on embedded device. We are using DirectFB as
>> > windowing system .
>> >
>> > We have cross-compiled and developed few basic QT apps, which are
>> > working.
>> > Now, we want to get the qt apps on Video window through DirectFB.
>> > Basically, want to create directfb surface using QT app on Video
>> > playback as
>> > ours would be a Single application.
>> >
>> > How can we get QT apps running on Video playback through DirectFB? Our
>> > SoC
>> > vendor has given a sample tool to start Video playback through DirectFB.
>> >
>> > Hope the problem is clear. If not, please let me know, will try to
>> > provide
>> > more details.
>> >
>> > Thanks and Regards,
>> > Poornima

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