Hi there, not quite sure if this is the proper forum to ask this, but you might be able to help me!

I was wondering if anyone has any idea why my phone wont play videos or sound through mhl hdmi on tv
menus and pictures works fine, but when i try to play a video it plays on phone but on tv screen just turns dark.
I am having Xperia T running cyanogenMod 10.2.0-mint (4.3.1 android).

Any help ideas would be greatly appreciated.

(so far I tried playing music, and opening any videos with default player and mx player, on all hdmi hangs. (black screen).

Have you tested that HDMI MHL cable on any other android device to see if it does the same thing? If it doesn't then I think it's a problem with your Xperia T's firmware. I would recommend you install the stock Sony firmware back onto your Xperia T and see if that remedies your problem.

Yea tested with samsung galaxy 2 and 4. worked fine there.

Good idea I actually thought a problem must be in firmware as from yesterday my phone started to hang and reboot after even plugging it on hdmi mhl cable.

Thanks for a suggestion ill try it out.

Yeah, it definitely sounds like a firmware issue. Which can occur from time to time when using custom firmware. That is the reason why I would only recommend using Stock Firmware supplied by the device's manufacturer.

I hope that will solve your problem.