[Development] The dark side of QtMultimedia

Kevin Kofler kevin.kofler at chello.at
Mon Nov 17 20:00:23 CET 2014

Thiago Macieira wrote:
> > > Developers don't care about having the latest version, they care about
> > > getting work done.
> I understand, but that only supports my point. So it wasn't the distros
> that were shortsighted, the upstream developers were.

But users do care about everything using the latest GStreamer, because it 
means that they don't have to install 2 different versions of the codec 
plugins and that they benefit from the improvements in codec support in the 
maintained GStreamer branch. Not shipping GStreamer 0.10 by default (while 
still having it available in the online repository) also saves a non-
negligible amount of space on our live images.

Plus, in the GStreamer case, there's also the problem that several things 
drag in GStreamer indirectly through, e.g., QtWebKit or Phonon (the latter 
also being dragged in by some KDE libraries/frameworks), and then if 
QtMultimedia uses a different version, we get symbol conflicts and crashes. 
(And it wouldn't be fair to blame GStreamer for that because Qt does not 
support this situation either and will also crash if you link different 
major versions into the same program.)

The latest versions of some GStreamer-using libraries (Phonon, kde-telepathy 
and many of the non-Qt libraries) already only support GStreamer 1, which in 
turn forces us to build some other libraries against GStreamer 1 (e.g. 
QtWebKit), so we effectively cannot fully support a GStreamer-0.10 
QtMultimedia on Fedora anymore. (Using QtWebKit and QtMultimedia together 
will crash your application if QtMultimedia uses GStreamer 0.10.) We will 
probably be shipping the experimental GStreamer 1 patches, and I'm even 
considering backporting them to the Qt 4 version of QtMultimedia.

> By the way, I read somewhere that some distros are considering not
> shipping Qt 4 as early as their next releases. I also think that's
> shortsighted. Keep it in your repos all the way into 2017...

Fedora will not do that. I also consider that a major disservice to those 
distros' users. We still ship even Qt 3 (of course only in the online 
repository) in Fedora. GStreamer 0.10 is also still available, but there are 
practical issues with things using the old version, as explained above. So 
we really want everything ported to the latest version as soon as possible.

        Kevin Kofler

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