Why use higher than NTSC?

[wadiator]

Here's something I don't understand: I am capturing via S-Video feed off of DirecTv. This should give me almost the best quality feed (next to component video) possible. Even so, though, isn't all non-HDTV video in a 352x240 or so format in NTSC? That being the case, what difference does it make if I capture at a higher rate? Why would that give me a better capture. It would seem to be the same thing as getting paid in pennies each week. Yeah, I have more pennies (pixels) but they add up to the same thing.

Am I just missing something here? I realize the loss in quality mainly occurs during compression. Therefore, if I capture uncompressed at 352x240, isn't that as good as it gets and anything else just muddies the water? Why use 480 x 480 on a normal television show?

My theory is, capture uncompressed at native resolution and then compress the original until you get what you're happy with. Eh?

[willy_annand]

NTSC is actually 352x480. It is interlaced to 352x240 and each frame has 1/2 the picture.

[patrickm]

NTSC is actually 480 analog horizontal lines. generally, it is spec'd at 720x480 or 704x480 digitally, which correlate pretty well to the number of pixels in horizontal scan line of a tv set.

the horizontal resolution really correlates to the frequency response to an analog signal that a tv is capable of displaying.

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[medievil]

yup, NTSC is definately 720*480, capturing at 352*480 will give a significantly more dull picture. if possible ALWAYS capture at 740*480 you can always resize later. Some say it overkill to cap at 720 for VHS but I disagree.. Capturinf at 740 will ensure you get the full badwidth your iinput is capable of recieving, regardless of the source.
I personally can see a dramatic increase in quality on all capture sources.

[wadiator]

Well slap me and call me uninitiated! That's awesome. I will have to try some higher bandwidth captures and see what happens.

Now, this brings me to another question, then. Shouldn't I get a sharper picture from DirecTv if they introduced a progressive scan receiver / they put out a non-interlaced signal? Or are most shows broadcast from the source as interlaced? I'm aware that more and more shows (newer ones) are being filmed/shot at higher quality. But what about reruns? Were they actually stored to tape in some sort of interlaced format.

I guess I'm just curious about the source(s) and what the possibilities are. I would think that, given DirecTv (Dish Network) controls their environment a bit more than cable companies (shooting raw info to the decoder for the decoder to decide how to spit it out), they should be able to produce a better picture to a multi-sync tv like a big-screen. I have a Hitachi 60SDX that's a real bad boy but I can tell with normal tv I'm not getting all there is to get, if you know what I mean.

Comments are much appreciated. I've learned more in one post than an hour of 'googling' the web.

[wadiator]

Oh, one other thing after re-reading the posts again. If each frame only contains half the picture, how is capturing picking up the other half?

[solarfox]

Yes, older TV shows that were originally shot/edited on video were recorded in an interlaced form on the videotapes. (Which doesn't mean they couldn't be de-interlaced by the broadcaster later, if they were to be rebroadcast over a progressive-scan satellite-TV system.)

If each frame only contains half the picture, how is capturing picking up the other half?

Because willy_annad is confusing frames with fields. A frame contains the entire picture, made up of two fields. One field contains all of the odd-numbered scan lines, the second contains all of the even-numbered ones -- so, each field makes up 1/2 the picture, and when combined together they make up one complete frame.

[crahak]

Oh god. Capturing at 640x480 is a good thing (or 720, whatever), but you don't get that many "real" pixels.... Many in depth posts and articles about it. NTSC calls for lines, not a resolution, D1 is 720x480... Not quite the same story. Also, I've recently had feeds off my satellite with only one field, leaving me only 240 useable lines (and letteboxed, that is)....