Originally Posted by Gary McCoy
OK, I'm going to venture a guess here. Some of you still own HDTV's from before the NTSC analog broadcasts were turned off. In other words, you have sets with BOTH ATSC digital and NTSC analog tuners built in. In the days when both ATSC and NTSC broadcasts were happening, these sets switched between digital and analog tuning modes automaticly as you scanned the airwaves.
If that's the case, since the only over-the-air broadcasts remaining are ATSC digital broadcasts, you have NO REASON WHATSOEVER to need the overscan feature, it is a legacy feature left over from now-obsolete NTSC tuners.
Digital broadcasts do not make use of a "blanking interval" between fields or frames to contain other data. With digital broadcasting, the pixel values, the sync timing, the audio, the closed captioning, and everything else are just seperate data sets, multiplexed together for broadcast. There is no data physically adjacent to video signals, and overscan is not needed to conceal the artifacts on the edge of the video frame - because there are no such artifacts.
The NEXT HDTV you buy doesn't need an overscan feature.
You may be correct theoretically.
I have a Sony EX710 which can be set to eliminate overscan, fed an OTA signal by my HD Tivo. On my local ATSC channels I often see the data band at the top of locally produced SD content upconverted by the station and broadcast on their HD feed if the set's overscan is disabled. This occurs during local news on stations not equipped to broadcast locally originated programming in HD and on locally produced SD commercials. I don't bother to turn on the overscan for the local news on these channels so it's no big deal.