Raspbmc UI flickering, virtually unusable

Question

I just got Raspbmc up and running on my TV...except that it is flickering like crazy. It's flickering so bad, the skin almost looks like complete noise. I can make out the text in the menus, and navigate with the TV Remote, but that is the extent of what I can do. I thought that it could be a problem with the resolution, and when I tried to change the resolution to 720p, it changed back to 1080p.
I used the following setup:

• Raspberry Pi model B
• Ethernet cable
• HDMI Cable
• 4GB Class 4 SD Card
• Panasonic LCD TV
• 5V 1A charger (iPhone charger)

I have no idea what's going on. I even reinstalled Raspbmc to no avail. Help would be greatly appreciated.

Answer 1

I would start by testing that the HDMI cable isn't faulty. If you have a second cable, try plugging this in and see if it fixes the problem.

If not it could also be the length of the cable(s) in which case you will need to change the configuration options for config_hdmi_boost.

Try upping the value to 4 for example.

You can read the instructions here:

Changing RPI configuration

If that doesn't fix the problem I would then try another TV/monitor if you have one. Assuming you can try this, if it isn't an issue on the second device it is probably an issue with your TV or the power unit.

If you have a second power unit try this out as well and see if it fixes the issue.

At that point I would also try the debugging steps on eLinux:

RPI Display Troubleshooting

Answer 2

I had a similar issue, I used the Pi on two different screens one using an adapter to VGA and one direct to HDMI. I seemed to have two options, manually select a refresh rate and resolution by editing the HDMI config as has been discussed or by having the Pi auto detect, truth is most distros don't detect the display early enough. The answer for me has been to install the distro using NOOBS. Seems to detect the display first, then hand that display state to the distro's boot sequence. It's certainly not ideal.