After getting cable installed, I was disappointed at the quality of the HD signal - particulary for football. I was seeing what looked like jaggies especially in cases where it was a white color (like a jersey or field line) on a dark color (like the field). The image wasn’t like that before I moved, so I figured it had something to do with the new environment - maybe some bad cables, shaky power, a bad cable box, or maybe just different compression used by Comcast in this area.
After a little fiddling and googling, I figured out what the issue was. Assuming you have a box that looks something like this (I didn’t bother checking if I had this exact model or not) you can get to the imaging menu by powering the box off, and then hitting the menu button. That brings up a few options - one of which is the resolution that the box emits over its Component video (YPbPr) outputs. By default, it was set to 480i. As soon as I cranked that to the more appropriate 720p those problems almost completely went away. I still have some tweaking to do, but in case you find yourself in this situation, don’t forget you have to power the box off to get to this hidden menu.
