QtMultimedia V. Phonon -- The full story?

[Kevin Kofler]

Ryan Rix wrote:
> I'm currently trying to start a KDE beat for next week's Fedora Weekly
> News, and was hoping I could get a little clearing up on the whole state
> of QtMultimedia in Qt 4.6.

I'd second Eike's recommendation not to mention Phonon yet, we don't have 
all the information we'd like to have ourselves at this point.

In any case, some of the things you wrote are incorrect:

> What I know:
> * Qt pulled Phonon into its API for the 4.4 release.

Right.

> * QtMobility is creating a second Multimedia API which will be lower level
> than Phonon which will be in Qt 4.6 under a QtMultimedia namespace.

Wrong, you're mixing up 2 things:
* QtMobility is creating a second Multimedia API which they see as replacing 
Phonon. It will be on basically the same level as Phonon (though a backend 
wrapping Phonon is being considered).
* There is a low-level (direct PCM access) audio API which will be in Qt 4.6 
under a QtMultimedia namespace, complementing Phonon (which still doesn't 
have a low-level API (one was started on a work branch, but never made it 
into trunk, and it only has an ALSA backend, more would be needed for 
portability)). The QtMultimedia stuff appears to have backends for all Qt 
platforms.

Those 2 sets of classes are separate (though they may (or may not) end up 
merged under the QtMultimedia namespace in a future version of Qt).

> * Fedora-KDE will be meeting next week with the upstream (kde) developers
> regarding the future of Phonon in KDE.

Not exactly true either.

We will try to gather feedback from upstream over the next week and discuss 
the matter again next week in our meeting based on that feedback. (Another 
reason why this shouldn't be covered this week, the discussion got postponed 
to next week at the earliest.)

> * Some Fedora-KDE members (Kevin, Sho_, Rex(?)) believe the API to be
> inferior

It's not just inferior, it's also not ready yet and will be incompatible 
with Phonon, so KDE apps will continue using Phonon for the foreseeable 
future.

> and may end up becoming the main Multimedia API in Qt

That indeed seems to be the case.

> as Phonon becomes older and older (via IRC logs)

Phonon itself is actively developed, what we're worried about is that the 
copy inside Qt will be bitrotting.

> What I don't know:

Well, we don't know for sure either. But as far as I know:

> * What does this mean for KDE for KDE now, KDE4.4 (which will be on Qt
> 4.6?) and the future of the project in general?

Not much, KDE will just continue using Phonon.

Our worries are about the future of Qt's bundled Phonon (which is the Phonon 
we're currently shipping in Rawhide, also because of the circular Qt-
>Phonon->Qt dependency due to QtWebKit using Phonon) and of the Phonon-
GStreamer backend (which is primarily maintained by Qt Software).

> * Will KDE apps begin using QtMultimedia (or a KDE derivative) over
> Phonon?

No.

> * How do Fedora-KDE developers feel about this possible change and
> the new API in general? There is, as always, both sides to the issue and I
> want to capture both.

My personal opinion: It just reinvents the wheel for no reason and is yet 
another incompatible API. This continues the pattern of Qt reinventing 
inferior versions of kdelibs functionality, ending what was marketed as the 
first success story of KDE-Qt cooperation. We're back to the times of KDE 
and Qt containing duplicate functionality because KDE's version was there 
first and is better in many ways. :-(

The QtMobility folks claim Phonon is incomplete because it's missing 
features X, Y and Z, but when you research things, you find out that X is 
already implemented in Phonon trunk which Qt doesn't seem to be interested 
in merging, Y is being implemented and Z is planned, but nobody bothered 
working on implementing it (so the QtMobility folks could have done it 
within Phonon instead of reinventing the wheel). For example, extracting 
single frames from a video (useful e.g. for thumbnailing) is one such 
"feature X". On the other hand, their stuff isn't even usable yet.

> Sorry if I sound ignorant on the subject (I am) and thanks for helping me
> out. This'll be in FWN next week under the (new) KDE beat if I can get a
> handle on this issue.

To be honest, I think that if FWN wants to cover KDE stuff, somebody who 
follows the discussions on #fedora-kde and knows what they mean will have to 
do it. (For example, I believe everything I wrote about Phonon in this mail 
was said on #fedora-kde at some point.) Somebody as confused as you are will 
just misinform users. :-( Sorry for being blunt…

        Kevin Kofler