Why is the picture better when receiving cable HDTV programming rather than Std programs,on my Std. Def TV?

Question

Mitsubishi VS-50705, Composite video in, 850 lines resolution. Cable box set to 480i STD. Am I getting the full 850 lines (or close to it), even though the box is set to 480i?

Geoff's response really did not answer my question. The picture detail is significantly better when tuned to an HD channel compared to the same programing on the std. channel. For example, the picture on ESPNH has much more detail than ESPN. It is similar to the picture definition when playing a DVD, almost HD quality (letterboxed on my 4:3 screen). What I'm asking is whether it is because I'm getting more lines of actual pictire information from a HD channel that my set is able to resolve, even though the cable box is set at 480i?

I'm afraid TV guy didn't really answer my question either. On std. channels, my digital cable box is also delivering a digital signal to my TV. I am not comparing analog to digtal here. When I tune to the HD channel, it isn't less noise I'm seeing, it is higher definition, more picture information. Since the TV is capable of displying 850 lines, my question again is: even with the cable box set to 480i (the only output the TV will display), does the set top box actually deliver more lines of information to the TV in an HD signal than a std. signal, such that my TV is actually resolving more lines? Or, on the std channel, (as TV guy suggests) is the set top delivering less than 480 interlaced lines? This doesn't seem plausible because I thought that a standard digital TV channel is indeed 480i.

Answer 1

All HD programs are transmitted in digital format. Even though your set-top scales down the HD signal to 480i, you get the advantage of a noise-free digital signal and 480 lines of resolution.

Analog cable may have less than 480 lines, has more noise and will definitely look worse than the digital channel.

Your TV scales up the input 480i to its native resolution. Since your digital signal is cleaner, the scaled version will also look better.

Answer 2

If the box is outputing only 480i, then you are only getting 480 lines of resolution. The TV will blow this up to 850 lines. A 480i picture does look better on an 850 line set, just because you can't as readily see the black spaces in between lines like you can on a 480 line set with a big screen. It's just that an 850 line set needs to draw most of the lines twice.