My Sony Xperia Acro S has a micro HDMI out connection. I have connected it via an HDMI cable to several HDTV's and have no problem playing Youtube, Amazon Prime and others at various quality settings.
The Slingplayer App however, will only display content full screen on the HDTV if it is in SQ or Auto mode. If I switch to HQ mode, it 'squishes' the image to where circles are now tall ovals (aspect ratio ends up as 4:3). Using the zoom and aspect ratio tools on the app have no effect. The only way to get output back to fill the screen (correct aspect) is to switch to Auto or SQ. Bit rate on my home LAN is generally 3,000kbps.
I also should mention that when this happens the video on my phone's screen looks fine.
Phone is running Android Jellybean. Slingplayer app is latest version on google Play Store.
Again to clarify this is via regular HDMI out using a micro HDMI connection on my phone. This is not an MHL connection.