Can all applications recognize Gnome shortcuts for multimedia keys?

Recently I installed MPlayer with its default gui and its interfaces SMPlayer and GnomeMPlayer. When I’m using GnomeMPlayer it responds to multimedia keys as configured in Gnome shortcuts, even if it’s minimized or running in another virtual desktop. But it doesn’t happen to the other two gui’s mentioned above. I have also noticed that native Gnome applications or with Gnome support like Banshee and Rhythmbox rspond to multimedia keys even when the gui is closed and they are running only in the system tray. But it never occurs in non-Gnome applications like VLC, MPlayer and others. Jetaudio wich responds to these keys in MS Windows running under Wine doesn’t even recognize them.
So I came to the conclusion that only native Gnome applications or with Gnome support recognize multimedia keys because, as it seems, they receive the signal from Gnome configurations. Others applications doesn’t do so.
Here is my question:
Is there some way to make all applications recognize the configuration of Gnome multimedia keys shortcuts? (Of course it would not be fine if they recognized ALL Gnome shortcuts because they could conflict with shortcuts from another applications. The idela would be that they recognize ONLY Gnome multimedia shortcuts.)

I believe your conclusion is correct. Apart from the X-defined multimedia keys that you can list with

~> xmodmap -pke

most gnome apps will adhere to gnome shortcuts, as kde apps do for kde shortcuts. Apps that are not DE-centered will have whatever their developers decided to use (usually X standards, where applicable).

You can, however, see what keycodes are generated when you press them with

~> xev

and use xmodmap to remap them to the key your app expects to be pressed. As this may conflict with other apps (and is a pain to understand and set), be careful to check first if you can’t reconfigure the shortcuts in the app config dialog.

For example, SMPlayer shortcuts are configurable in it’s settings menu.

But note that most multimedia apps are set to recognize X multimedia keycodes (or keysims, there’s a translation step somewhere), like, in my system:

keycode 160 = XF86AudioMute (when you press the "mute" button)
keycode 176 = XF86AudioRaiseVolume
keycode 233 = XF86Forward

and so on.

Some tips here: Multimediakeys with .Xmodmap HOWTO

Very interesting. I didn’t knew the tips you mentioned above.
I tried, for example, to configure shortcuts in SMplayer and in VLC using the preferences settings, since both have a section to configure keyboard shortcuts, but when they asked to press a new keys to be a shortcut and I pressed one of multimedia keys, nothing happened. Trying to type the code they generated in xmodmap didn’t work too. The seems to be that these keys are not recognized as part of the keyboard layout. I entered the keyboard section in Yast and it’s very limited. It only lets us choose one keyboard layout, nad none of them have any mention of multimedia keys, and have some other few options that have nothing to do with what I’m searching for.
Is there some system or conf file where we could edit the keyboard layout manually and and include multimedia keys on it? Or is there some downloadable and installable layout for Opensuse that do this automatically?