Connecting HDMI to HT for Picture is not a good idea specially for dth . that surely effect the pq from dth. the ht upscale the pic like in all picture output. all know TV also upscale the picture to certain extent. there is differance in stream from one dth to other dth stb. for getting Dolby Digital audio it is better to connect through Optical or coaxial cable. connecting HDMI directly to TV will give the best pictures.
airtel hd pictures are very good but have more brightness than tatasky . tatasky have good contrast but less brightness, videocon have very less brightness but good contrast. Dish TV HD Channels have best pq compared to all other dth. problem is they have no Dolby digital audio in very few channels.
All brands of HT is not giving the same Picture output as they recieve in HDMI . few features downgrading the Picture. for example Onkyo HT has a feature for adjusting Normal,Dim ,Dimmer. this is effecting the actual Picture quality for dth input . .