Axiom Home Page Forums General Discussion Home Theater Digital video?

Craig, you got it right regarding the DVI (DVI-D) versus Component connections. With the DVI-D connection, the video signal remains in the digital domain from start to finish, eliminating the possible degradation due to D/A and A/D conversions.

Regarding 480p, 480i, 720p, et al., the number designate the horizontal resolution or pixel counts. The "p" and "i" subscripts are for "progressive" and "interlaced," respectively. In the interlaced format, a half of the entire image content, consisting of odd-numbered horizontal scan lines only, is sent first, followed by another half of the image consisting of even-numbered scan lines sent 1/60 second later. These two image "fields" will make up one complete image "frame" every 1/30 second. In the progressive format, a complete image (frame) is simply sent every 1/30 second. The interlaced format is invented early in the history of TV broadcast, in order to prevent CRT screen flickers.

In this era of big-screen TVs, however, the problem of interlaced video format is the fact that the objects in the scene can move between the two consecutive fields (i.e., within 1/60 second), resulting in the nasty "combing" artifacts. This wasn't a big deal when the TV screen was small and the picture quality was compromised anyway by other factors such as the artifacts associated with the analog over-the-air broadcasting.

The "native" format of DVD media is 480i. When a 24-frame-per-second film material is converted onto DVD, they perform what's called 2:3 pulldown -- the first film frame is copied into three consecutive 60-fps interlaced DVD fields, the second film frame into two following DVD fields, the third film frame into the next three, etc... That way, two 24-fps film image frames are converted to five 60-fps interlaced DVD fields in order to preserve the final frame rate (you need a bit of math to understand this: 24/2 = 60/(2+3) ).

All fixed-pixel digital displays (plasmas, DLPs, LCDs...) are inherently progressive. In order to display the 480i DVD image on a big-screen TV with a good image quality, you need to "deinterlace" the 480i signal to the 480p, 720p, or 1080p progressive format. A good deinterlacer chip will automatically detect the 2:3 pulldown sequences of film-based materials, and reverse the pulldown process to generate the 480p video sequence in which the original film frames are perfectly restored. Deinterlacing the video-based materials is MUCH more complicated, because you have to intelligently interpolate between the consecutive 480i fields and compensate for the motion artifacts (combing). The Faroudja DCDi and other reputable deinterlacers are extremely good at doing these tricks, in addition to correctly detect the 2:3 pulldown sequences.

The most common HDTV format (either satellite, cable, or over-the-air) in the US is 1080i, followed by 720p as a distant second. SDTV broadcast is always 480i, same as DVD.