Then you have wired something wrong. I had an iPod Video connected to my BMW TV system in my E39, and it sounded fantastic, without altering any tone controls.
Check your wiring!
I had L&R together, connected to the audio in
And ground to ground of course.
Don't forget, the AV input is only mono!

Only by "tricking" the system to have different video and audio inputs active.
eg, you are asking for:
Video = AV in
Audio = Aux-In
to do this you need to add an extra module that then responds to certain key-presses and switches the inputs accordingly.
You can either build one if you know how, or buy one - search ebay or google for it.

I understand that, but, Can I connect sound to the aux on radio module BM24, and video on tv tuner.can work simultaneously?

Only by "tricking" the system to have different video and audio inputs active.
eg, you are asking for:
Video = AV in
Audio = Aux-In
to do this you need to add an extra module that then responds to certain key-presses and switches the inputs accordingly.
You can either build one if you know how, or buy one - search ebay or google for it.

So the answer is YES YOU CAN BUT ONLY WITH EXTRA HARDWARE MODULE

Which modules support this kind of functionality? I started compiling a list here.

Thanks

I was referring to DIY, where you make your own. Requires electronics and programming knowledge.

Jochen, could you give me any starting pointers? My programming is ok, but hardware might prove more difficult.

Can you do this trick issuing the right commands on the iBus interface?

Use a PIC with a RS232 port, and then a proper ibus interface chip with auto power shutdown

And yes, it is easy to generate the commands via the ibus to have independent video and audio sources, controlled by any key press you desire.

Would the RS232 iBus interface of Rolph Resler work?

Well the Resler interface provides the ibus to RS232 conversion but you still need a PIC