Is it possible to capture from VHS better than 352x240 NTSC?

[fandecine]

Hi!
I have a ATI AIW Radeon 7500. I am trying to capture some VHS tapes to SVCD (480x480). So I captured at 640x480 with Virtual Dub but got problems with the picture quality(double lines?). So is there another setup to convert VHS with the best quality? I have 45mn to put on each CD.
Also, still with Virtual Dub, I have some problem to capture my PAL VHS tapes. I put 25fps but get a horrible preview. Is there something else I have to do? (Of course, I am using a multisystem VCR).
Thank you for your help.
LD

[miamicanes]

VHS has poor horizontal resolution (comparable to, say, 120-240 smeared and blurry horizontal pixels on a computer), but has 480 lines of potential vertical detail. However, the 480 lines aren't razor-sharp, either -- with the exception of videogame output, they're almost always blurred together a bit to avoid situations with a bright horizontal detail ocupying only a single line is surrounded by darkness, because it'll flicker horribly (think: TV weather radar images and the like). Still... VHS has VASTLY better vertical resolution than horizontal resolution... so you should preserve all of it if you can.

If you're doing digital noise removal between capture (to HuffyUV, MJPEG, etc) and compression to MPEG-2, you might as well capture and render at 704x480 -- MPEG-2 encodes detail and sharpness, not "resolution" per se, so 704 semi-blurry pixels that really convey 352 pixels of detail will end up taking the same number of bits to compress as 352 horizontal pixels conveying the same image. If you're NOT performing noise-removal, capture to 352 x 480.

The only real downside to 352 x 480 is that some DVD players (like the Pioneer DV-525, admittedly 3 years old) have an annoying tendency to periodically not expand the 352 pixels horizontally to take up the full width during transitions between ffwd/rew and play (in other words, if it's playing, you hit ffwd to zoom forward, then let go, it might squash horizontally for a fraction of a second then go back to normal during the transition).

If you're recording to CD-R, 352 x 480 MPEG-2 is the "golden" resolution to strive for, because it's the only one that's common to both a CD-R format and DVD, so when you get a DVD writer someday, you'll be able to rip and copy it to a DVD without re-encoding the MPEG. Technically, 352x480 isn't "VCD" or "SVCD", it's a mode called "CVD" (sometimes lumped under "XVCD") that nevertheless most DVD players capable of handling VCDs can handle anyway.

One big rule, though -- if you're capturing to 352x480 or 704x480, DO NOT DEINTERLACE IT. If you do, the resulting video will look nice on your computer, but look "unreal" and "weird" when viewed on a normal TV. Why? Compliant DVDs store 60 interlaced fields of video for each second. Each field represents a different moment in time. If you deinterlace it to 30fps, the DVD authoring software will still split it up into 60 fields, but now each pair of sequential fields will represent the same 1/30th of a second rather than two sequential 1/60th of a second intervals. So you'll have effectively cut your temporal rate down to 30, introducing judder. But wait, it gets worse.

Deinterlacing algorithms mainly strive to minimize weave artifacts and preserve vertical detail. They do a remarkably good job. However, preservation of TEMPORAL detail is invariably lost and mangled. So each resulting 1/30th second progressive frame might/does convey some amount of "wrong" temporal information -- some of the details are 1/60th of a second behind, some are 1/60th of a second ahead. Your brain notices this, and notes that something isn't quite right.

The effect is always there, but it's the WORST when you convert 60 field/second into 30 frames/second. Converting 60 field/second to 60 frame/second doesn't introduce nearly as much error, because the algorithms are weighted to make detail from the previous and following fields fit into the order established by the current field. With 60->30, the algorithms tend to treat the field pairs as interchangeable and just grab whatever data is easier to use at the moment.

[txpharoah]

Try the VHS->DVD guide in my signature. It's for ATI cards to make perfect DVDs from VHS.