Although Helix is another one, but I don't think it'll have much success since Real Networks being the original developer.
Anyhow, for sometime even KDE used Gstreamer as their main multimedia framework (in apps such as Amarok, etc). Although Gstreamer developers say that they have nothing to do with GTK or Gnome... but many see (including myself) a lot of similarities between Gnome and Gstreamer (they both start with the letter "G", okay, that was a bad example :/). So it's natural for KDE to have/build something of their "own".
It may have not been the only reason... anyhow, that's one of the reasons how Phonon was created. It consists of main three parts according to KDE themselves, quoted below...
MediaObjects, Paths and Outputs. The MediaObjects control the playback/capture and provide the media data. MediaObjects can be connected to Outputs using Path objects which also allow the insertion of Effect objects between MediaObject and Output.What is a multimedia framework?
To be honest, I'm not a programmer, so I don't have a in depth concerning its "tech" aspects. But between you and me :)...
... When designing a multimedia framework, the original developers make sure to built/embed codecs, libraries + many more that are necessary to playing/capture the audio/video files from reading the original source file to "carrying" it to your GNU/Linux PC/Laptop's speaker (output).So anyone who knows standard layout, can easily implement it on their "projects"/players.
Most importantly, this is done within a standard "layout" (API). That's why it's called a framework :).
Let's say that you're a developer who'd like to create a multimedia player of your own. Then you'll have to figure out how to read/play all sorts of codecs (hundreds and hundreds of 'em, Xvid, Divx, AAC, MP3, Theora, WMV,.....), etc and implement all that to your video player, despite of the GUI creation using GTK or Qt or any other that you like (you know creating a graphical "player" with buttons and stuff).
So, it's pretty boring and hard work (who likes that :P). But with a multimedia framework, since they've done all the hard work for you (such as building programming codes for playing all those different codecs, etc), all you have to do is built a GUI and simply "attach" the multimedia framework to the "player". So, whenever a user requests a file to play via your GUI, all your GUI does is just calls for the framework libraries and give the job to them.
So, a framework not only helps to create not just multimedia related things, but any other area, with ease + most importantly, it helps to bring applications that have different GUIs yet if they all use the same single framework, then it adds more stability to the software environment it self since, if a bug is detected or if new feature is added, then all those apps that use the framework can easily "get"/implement it.
Geeeeeez, this is getting awfully long. Wha was I saying again, oh yeah, Phonon. In the very recent past Phonon's main web site didn't look that good. I mean, when considering the high standard set by Qt or KDE artwork in general, it was a bit "behind".
But according to a phonon developer (who's still searching for a sensible wordpress pink theme :) ), few days ago they've give the official Phonon website a new look-n-feel and it looks GORGEOUS!.
The website design idea came from Tomasz Dudzik which was then became a reality via Wojciech Ryrych (nicely done) and according to them, the site is still being developed... which makes sense, since it seems to be lacking a nice introduction, etc.
Anyhow, the above mentioned Phonon developer-dude (maybe a girl... the obsession with "pink" :) ) is a very humble person, so if you have few ideas of your own on what's the site's "missing" then, please by all means, visit his/her site and throw some comments at him/her.
And if you want to express your love towards Phonon by making its logo your background for a while, then get it from here (high resolution, 2MB in size).
Again, I looove the "new" website, nicely done.