NTSC VHS to PAL DV, problem with the standards

[cheeseplease]

I had a VHS tape a while ago and it was NTSC

I needed to make a backup of it, so I gave it to a video conversion company who recorded the NTSC VHS stuff to PAL DV tape for me.


Now I have this PAL DV tape here and I'm workin with it now in order to make a PAL DVD from it. But I'm worried about the conversion the guys have done. I have the DV video in TMPEG now and I'm coding it over to DVD MPEG2 PAL, but there are some thin lines on the footage visible on the TMPEG preview screen, and I'm pretty sure they have to do with the NTSC to PAL conversion done earlier.

now I dont have the source NTSC VHS available any more, so is it possible to fix these errors now? would it make any sense to convert the footage back to NTSC? thanks for any ideas and help!

[choirislife923]

there are some thin lines on the footage visible on the TMPEG preview screen, and I'm pretty sure they have to do with the NTSC to PAL conversion done earlier.

it sounds like an interlace problem. have you tried switching the "_ frame first"? tmpegnc tends to do bottom frames first, so switch it to top. if that does not work, try progressive.

[cheeseplease]

Okay, I'll run TMPEGEnc with 'Field order' switched to "top field first" now, as this was set to bottom field before.

I guess you mean 'top field first' when you said 'top frame first'?




By the way, what exactly is the difference between interlaced and non-interlaced video? I've never been really sure what interlacing is for and what it affects... can anyone explain it to me? (I guess this has nothing to do with the NTSC to PAL issue I deal with here, I'm just curious to know about it anyway).
Thank you!

[choirislife923]

By the way, what exactly is the difference between interlaced and non-interlaced video?

back in the 1950s....NTSC was developed. however, since radio frequencies could not transport a whole big frame at once (remember, uncompressed analog video...i think its 110mbps in digital world [need to get dvd demystified book out...]), the frame was split into two - a top field (every other odd line) and a bottom field (every other even line). this alloweed transmissions of television. however, the side effect is that in fast moving situations, you will see streaks of lines where the fast action is going because the action is going so fast that interlace could not keep up. an example: play GTA 3, stare at the screen and run around or speed down the street and do a sharp turn, you will see lines on the fast action part instead of an image. non-interlace on the other hand, display the frame at once, not splitting into fields, so everything looks like the way attened.

check here for all you ever wanted to know about interlace.

in summary:

in PC world: progressive good, interlace bad (and theoretically, yes this is the best way because you dont screw a frame up and fast action scenes dont look like blurry-vision with lines)

in TV land: progressive bad, interlace good (interlace uses less bandwidth [or at least in HDTV land, since with interlace, you have have up to 6 sub-channels within a channel stream if you use interlace], so you can do lots of other stuff. also, (i think) teletext and closed captioning rely on interlace [somebody please check on this, i'm pretty sure, but not sure enough]).