VHS Resolution?

[ApacheWraith]

Does anyone know what it is? I remember 3 something by 2 something, sorry, I know this must be a dumb question........

Apache

[kinneera]

Generally approximated to 352x240 (NTSC) or 352x288 (PAL).

[H@Mouse]

VHS is just, well, strange. 352x240 or 352x288 won't accurately reproduce it, but 352x480 or 352x576 seems to, but is obviously overkill. No, I'm not referring to SVHS, just simple VHS - personal capturing experience and, well, take a look here for some decent visuals:
http://www.cs.tut.fi/~leopold/Ld/ResolutionComparison/

I haven't tried it, but it looks like 352x360 will reproduce VHS... I need to try this. I emailed with him long ago, and he truly seems quite the expert.

- H@

PS: did an edit to correct the link... seems the A HREF stuff wasn't necessary. Argh - I forget the capabilities of each forum, site to site. If this doesn't do it, cut and paste to see it. (It's worth the effort!)

<font size=-1>[ This Message was edited by: H@Mouse on 2002-01-15 20:55:12 ]</font>

[kinneera]

Well, if you want to get more detailed, VHS is technically 480 vertical (2 fields, 240 each). Generally though, magnetic interference, tape head interference, etc. reduce the effective vertical resolution to well below that value. Higher quality tape run through higher quality VCRs/capture cards can probably perform substantially better than 240, though. This is why a lot of people find that it is better to capture both fields anyway, and then resize to 240 for VCD.

[ApacheWraith]

H, thanks for the link. SO when you capture from VHS, for example, are you making the image better? Isn't it a digital image once it becomes .avi? If you capture @ say 720 X 480 is the picture going to look better?

Thanks for everyone's input.

Wraith

[davidian]

Most people say that 352x576 is sufficient, but I've heard from other video experts that capturing at maximum resolution possible and then downsizing will give you the best quality.

I have not tried this so I have no idea wether it's true..

I've heard about ~10% better quality if you capture 720x576..

:.-)

[ApacheWraith]

Yeah, I captured a recent video at 720 X 480 and downsized it to 352 X 240 but after the encoding the video was moving like in fast forward and the sound was normal and they were really out of sync. I still can't figure it out.

Wraith

[H@Mouse]

I knew about the alternating fields in dubbing from VHS, but... you know, kinneera, that has to be it! It's an older VCR I'm using, but it was one of the earlier models with stereo, 4 heads, etc. (might even be a dolby deck???). Fairly high end for its time. I wondered why higher caps gave me better results. It's ALWAYS looked better than any VCD I've seen. I bet it's the deck.

It's just that, well, tape wears out. I'd like to move to SVCD, but the time length limitations are deathly restrictive. Varying the bitrate would help, but only so much, and with major degradation. I'm waiting for DVD recorders (AND MEDIA ESPECIALLY) to come down at this point.

davidian, AW, I could see why a higher res capture would be better and immediately doing a filtered resize while capturing (not a simple resize - don't try that on a P4, you'll need an Athlon there for the FPU work for certain) would make for a better capture. Since VHS isn't really 352, nor 320, it's a bit less (just going from the hard facts I've read), you get uneven stretching for it to make 352. Interpolating it out (by the hardware capture card) to 720 and bringing it in ought to give you a much smoother pattern, not as much hard doubling of pixels. Then running it through any good filter (not a simple resize) to downsize on the computer should give you a slightly crisper picture, frame by frame.

Then again, if you're bringing in the video and immediately compressing it in a lossy format (MPG2, MPG4, ATI, MJPEG, etc.), then you're going to see a difference right there. Using the same quality factor (compression level) on small and large frame sources will yield about the same size, ugly, squarish blockiness in each. HOWEVER, when you dither the frames down AFTER the capture and compression, you would likely end up with a better lower res sample. Unfortunately, upon saving this lower res sample, you may lose most, all, or MORE quality than grabbing it straight in to this size.

AW, as for your super speed video issue, it sounds to me like you lost every other frame in the resize, but it still set the FPS the same to the old audio track. I bet something was set incorrectly for interlaced decoding. Might be a bug in the software though too. Good luck!

- H@

[kinneera]

<TABLE BORDER=0 ALIGN=CENTER WIDTH=85%><TR><TD><font size=-1>Quote:</font><HR size=1 color=black></TD></TR><TR><TD><FONT SIZE=-1><BLOCKQUOTE>
It's just that, well, tape wears out. I'd like to move to SVCD, but the time length limitations are deathly restrictive. Varying the bitrate would help, but only so much, and with major degradation. I'm waiting for DVD recorders (AND MEDIA ESPECIALLY) to come down at this point.
</BLOCKQUOTE></FONT></TD></TR><TR><TD><HR size=1 color=black></TD></TR></TABLE>

You might consider thinking about SVCD again. Using a good variable bit rate encoder and some very smart filtering, you can often produce very nice SVCDs (or XVCDs) that fit 60 min to an 80 min CD. I was able to make reasonable reproductions of Hi-8, and that is certainly higher quality source material than VHS.

[H@Mouse]

60 minutes on an 80 minute CD is incredible! What bitrate did you end up using? What encoder? (And especially, what filters?)

I'm assuming you used Nero also, right? (I'm looking into getting 5.5 soon).

Thanks for following up with that comment, you may have made my day/week/month!

- H@

[kinneera]

Well, for 60min exact, the average bitrate is 1580Kbps (300 min, 2496 max for me). Depending on the exact length of your video, it will vary, just use a bitrate calculator. CCE 5-pass through Avisynth. Spatial filters are wonderful for reducing/eliminating noise, which greatly improves the efficiency of MPEG encoding. Temporal filters can also help. (Note I do use 352x480 rather than 480x480, as this is a standard resolution, whith theoretical portability to DVD in the future).

I use VCDImager/CDRDAO for authoring and burning. Nero (with standards compliance disabled if you use 352x480) will probably also work, though.