EDIT : This has been fixed, you have to blindly go to system settings and set it to 1080P

thanks to priteshmodi

here

http://gamrconnect.vgchartz.com/post.php?id=3568898

i'll keep the old Topic just for people who have this problem

i've made this thread a day ago.

http://gamrconnect.vgchartz.com/thread.php?id=114165&page=1

and two issues were hanging out on me, one of them is resolved but the other... well i don't know.

see i had tried plugging in an HD cord on my 360 to my tv and all i got was "usupported signal" and a black screen with only sound, i've tried messed about with the picture settings, reseted it to factory setting and tried a lot of googling and stuff, i thought my HD cord is broken, even though it works perfectly with my PS3, but even with that i bought a newer high priced HD cord and it still didn't work! , so i tried it on my living room's HD Tv and guess what.....

my LG tv loves the 360 but ..... my Sony Bravia hates it (damn sony fanbots).

and i don't wanna talk about more Sony, yall lying and Is gettin me pissed!

but i'm still looking for a way to fix it , i now have everything unpluged maybe it will work itself out idk ...so any ideas are welcome!

So let me help out for the later helpers...

Sony Bravia:

Xbox 360 - Not working

Ps3 - Working

LG TV:

Xbox 360 - Working

Ps3 - Working

--------------------------------------------

Anyway, have you tried connecting a component cord from the Xbox to the Bravia? If that works, try messing around with the video settings, maybe the Xbox isn't outputting to the HDMI, maybe its outputting to a different, empty port, like an empty Optical Video or Component port

it works fine with component but not HD.

i tried messing around with the settings but there is really that much to mess with.

Have you tried the Xbox 360 reset display method? If you dont know...

1) Remove disc from tray

2) Turn Xbox off

3) Turn xbox on USING the wireless controller

4) While its booting up, press and hold the Y button, then press and hold the Right Trigger. Continue holding down both buttons, until the console resets again.

5) If you did it right, it should re-reset the console, in turn resetting the display of the console, back to 480p through the HDMI, then you can edit the display from there.

*it may take a few tries, but good luck

http://support.microsoft.com/kb/911059

If you already did it, I can't think  of anything else

EDIT: Edited a few things for clarity

Yeah i already did that a lot of times.

Are both your bedroom and main living room TVs the same size?

made the thread more interesting.

nope, living room is bigger , its not about the Res ,since my PS3 works fine remember?

No I was just gonna say if they were both the same size you could just switch them

Other then that I'm all out of ideas.

can't help you, but I've googled the problem and you're not the only one where a 360 doesn't really work with a Sony Bravia via HDMI.

http://forums.whirlpool.net.au/forum-replies-archive.cfm/1152764.html

http://www.avforums.com/forums/xbox-360/1200798-xbox-360-sony-bravia-hdmi.html

Though doesn't look like a general issue either.