Distorted sound when playing music from iTunes library (aTVflash black 1.1.1)


I listen to my iTunes music through my AppleTV (Black, firecore version 1.1.1) .
My TV is connected to my stereo set, using the audio-output from my TV. TV sounds are fine. Only when i play music from AppleTV, the sound is all distorted.

When i listen to the same tracks through my Mac directly ( i checked with headphones) , everything is crystal clear. There is nothing wrong with the tracks. At first i thouht maybe it could be caused by a sub-optimal wireless connection, and my laptop was to far away from my wireless router. So i moved my laptop close to my accesspont to check, but it remains the same bad distorted sound. 

Is this a known issue? What can i do to resolve this?