Audio and Video over HDMI with Ubuntu on Dell Studio 15

If you have a notebook or pc with HDMI output and a big LCD TV with HDMI input, you might want to connect those. Unfortunately, this doesn't work out-of-the-box with the Dell Studio 15 notebook, neither with Vista nor with Ubuntu.
Now I got it working both in Vista and Ubuntu (8.10 - Intrepid Ibex).

In Vista I needed to update the AMD ATI Mobility Radeon™ HD 3450 driver
download Vista driver from Dell.
Then you need to configure windows to use the HDMI audio output.

Enough about Vista, how about (Ubuntu) Linux?
I tested this in Ubuntu 8.10, but it should also work in 8.04 and 9.04. First you need the fglrx driver from AMD ATI. I tested it with version 9.6 (8.620) from ati.amd.com. You should read the docs and know what you're doing when you're installing new graphics drivers, because if anything goes wrong, you might end up without GUI, and for most users this is problematic.
First step after downloading the driver is building packages for your distribution, so I did:
sh ati-driver-installer-9-6-x86_64.run --buildpkg Ubuntu/8.10
This creates several .deb files, which I installed using dpkg (some packages depend on other, so order matters!).

Then you need to change the /etc/X11/xorg.conf file to make use of the fglrx driver, instead of the open source ati/radeon driver. You can do this running
aticonfig --initial
But, again, read the docs on the AMD website.

Cross you're fingers and reboot you're computer. If all went well, you now have X running with the fglrx driver. Connect the HDMI cable from you're notebook to the TV (and tune the TV to the HDMI input). Open the "Ati Catalyst Control Center" in the applications menu (it's listed under "other" on my system), or run "amdcccle" from the terminal. Go to the "Display Manager" in the Catalyst Control Center. If the external display is not listed, use the arrow next to the magnifying glass and chose "Detect Displays".
Now chose the monitor connected through HDMI, and click the "Multi-Display" Tab. Choose "Clone to Display X". The LCD TV should display your computer screen... but it might also be scrambled. If the display on the TV is scrambled, try changing the resolution in the "Properties" Tab, this solves the "scrambled image" problem for me (most of the times). If the control center notifies you that you should restart your computer... I've got this problem too, and somehow it disappeared, but sometimes it reappears... if anyone can explain this behaviour, please let me know.

Assuming you got video over HDMI now, the next step is audio. I used the program "Mumble" (an open source Teamspeak alternative) to determine what output the HDMI was. Mumble has an "Audio Wizard" which shows dozens of audio devices on my notebook and allow to test them. This way I assured myself that somehow Alsa was capable of outputting audio over HDMI.
I figured out the HDMI output on the Dell Studio 15 is "hw:1,3", so for mplayer use:
mplayer -xineramascreen 1 -fs -monitoraspect 16:9 -ao alsa:device=hw=1.3 file_to_play