Can I use QtMultimedia Private API ?

jpgehrig

Hi all,

I am experimenting with the new QtMultimedia module on Linux (Kubuntu 21.04). I would like to create a custom GStreamer pipeline by using some helper classes from the QtMultimedia/GStreamer backend. I have added multimedia-private to my QT.

My problem is that I get undefined references for some private classes.

For example, when I build this snippet:

#include "widget.h"

#include <QtMultimedia/private/qgstpipeline_p.h>

Widget::Widget(QWidget *parent)
    : QWidget(parent)
{
    QGstPipeline pipeline("my-pipeline");
    QGstElement element("videotestsrc");
}

I get:

undefined reference to `QGstPipeline::QGstPipeline(char const*)'
undefined reference to `QGstPipeline::~QGstPipeline()'

So QGstPipeline is undefined, but QGstElement is all good. Could anybody help me understand ?

I also tried with a CMake project by adding a project dependency to Qt6::MultimediaPrivate, same result 😕

Thanks!

SGaist

Hi,

From the looks of it, the class was not exported. I don't think it's intentional though.

jpgehrig

Bummer.

Can you point me to the files / docs I should look at to get the missing symbols exported. I am building Qt from source anyway and would be happy to contribute to QtMultimedia.

Dropping the plugin architecture in Qt6 is making everything so much simpler and interesting. I have a few apps which I want to migrate to Qt6 just to throw away custom Qt5/Multimedia code 😄

SGaist

From the looks of it, it's in gstpipeline_p.h. The other private classes seem to be exported.

jpgehrig

Amazing!

So I simply added Q_MULTIMEDIA_EXPORT to the QGstPipeline class declaration and it did the trick.

I'll try to get this contributed.

PS: Tu passes à la foire vendredi ?