Digital Video vs VHS to Digital Video Resolution?

[Shizuka]

Hello,

Please do not be laughing at me. I need to document this with a reliable source my boss will accept. (She will not take information from a website seriously.)

We are doing a behavioral study that requires a lot of digital video. We are using minidv cameras and transfering video in dv format and making mpeg2 video to use with our programs for analysis, then storing on dvd, but as data file. We require a lot of video above the 384X480 and above "legal" dvd resolutions, in order to see detail (subjects eye movements during task, etc).

Two sites do not want to buy minidv cameras. One site has Digital 8 and we think that should be good, too. One site has vhs cameras wall mounted. Their techs say that once they digitize the video, it should be the same as our mini dv. They are spending a lot of money to do this. My boss never thought it was a problem and did not mention until last Thursday. She is upset that it is a problem.

I thought that VHS, because it is analogue, cannot exceed 384X480 without losing quality, which will be paramount. I sited source in the cvd article, but my boss wants more acceptable source than a website or (she called it "chat room") online forum before she will break news to the site. Maybe book or magazine or journal article. I do not know how to find this source, since I am hobby-digital video person, not professional--I make web page and database for her. I thought the difference between VHS and digital video is obvious. Garabage in=garbage out. Maybe not. Please help.

Shizuka

[SatStorm]

This article I wrote, was a gathering of infos, floating in the Net the last 4 years!
For details, search on Chinish newspaper articles, about 98-99. All the infos are there, I know 'cause that was what I done myself to gather infos.

DVD - video has 4 legal resolutions: 352 X 288/240, 720 X 288/240, 352 X 576/480 and 720 X 576/480.
VHS officialy is 352 X 288/240, unofficially is more like 384 X 320 or something. SVHS is officially 352 X 576/480, unofficially is more like 400 X 520 or someting. CVD and 1/2 D1 picture DVD, are both full formats and both the best solution for VHS/SVHS source. CVD was forgoten (never exist outside china), but that doesn't mean that it is not a standard!

[pijetro]

Shizuka, you're right. Garbage in equals garbage out. Quality of video is very subjective, but getting to the quick answer about digitizing VHS. The answer is no!!! You can digitize the VHS to the point of being up to good as the VHS source, but you'll never exceed that. MiniDV, or D8(Sony's proprietary version) has a quality of around 702x480 (or 720x480). I forget the exact numbers, but you can see what I am saying. MiniDV resolution is much higher, and you don't have to worry about analogue to digital conversion.

Good luck.........

[BJ_M]

i could give you a lot of technical details on what is best and what camera's to use and so forth -- but 3 of the BEST - if not the best for expert advice even if you don't buy anything are as follows ... these people are very well respected in the industry and are well known ..

http://www.videoguys.com
http://www.dv411.com
http://www.bhphotovideo.com

[Xesdeeni]

Certainly VHS tapes will contain lower resolution than miniDV or digital8....potentially. However, you must also consider the cameras themselves. Depending on the camera, the actual image resolution may not be much better than VHS resolution. All digital camcorders are not created equal.

* Single-CCD cameras have only one sensor per pixel. But each sensor has a color filter on it to allow only one color (red, green, or blue) to reach the sensor. Typically in each group of four sensors, there are two green, one red, and one blue filters. The camera must then use interpolation of surrounding sensor information to obtain all three colors from each sensor position. This means each color has less than full resolution. Exactly how much less depends on the actual orientation of the filters.

* Most cameras use sensors with square pixels. However, miniDV/digital8 pixels are not square. So the camera must do a conversion.

* Cameras with digital image stabilization may sacrifice overall image resolution for image stability by using a smaller section of the sensor and scaling the data up to miniDV/digital8 resolutions. This allows a cushion of space around the image on the sensor for the digital stabilization to use.

All of this depends on the quality of the cameras you are using. All miniDV/digital8 cameras are not created equal. My Canon Optura Pi had an obviously higher resolution than my friend's JVC (sorry, don't know the model) when we shot two angles of the same scene and I began to edit them together.

Take a look at this:

The top two images are cropped sections of a frame from my camera, while the bottom two images are from my friend's camera, shooting exactly the same scene from a different angle.
(Note the VirtualDub bug on the right edge of each section )

To my eye, this looks like about half the horizontal resolution. Based on the compensations mentioned above, "full" resolution is very unlikely to be 720 pixels per line, but if we assume that 720 pixels were the starting point, this looks like it would be about 360 pixels per line. That is roughly equivalent to VHS, so it is possible that there would not be nearly as much difference between this camera and a good VHS camera's videos in terms of resolution.

Xesdeeni

[House de Kris]

Shizuka, your boss is wise not trusting the Internet as a reliable source. It is filled with blatant disinformation such as:

"VHS officialy is 352 X 288/240, unofficially is more like 384 X 320 or something. SVHS is officially 352 X 576/480, unofficially is more like 400 X 520 or someting."

You could check reputable sources and have theoretical discussions with your other sites, OR, you could just shoot some footage with the VHS cameras and see if they have enough detail for your analysis on a TV before you even bother to digitize. If the source isn't good enough to see facial details, then end of debate.

[SatStorm]

House de kris, I suggest you to take a swim before you post....

JVC is the creator of VHS and SVHS.
JVC said: VHS is 352 X 288/240 and SVHS is 352 X 576/480
The God spoken.

Anything else is bullshit.

[BJ_M]

House de kris, I suggest you to take a swim before you post....

JVC is the creator of VHS and SVHS.
JVC said: VHS is 352 X 288/240 and SVHS is 352 X 576/480
The God spoken.

Anything else is bullshit.

true (they also invented s-vhs and d-vhs) .. but what the other poster may mean is though the spec is etched in stone - in practise on some machines and sources you may get less.

[vhelp]

hay peoples..

All I know is.. when I look at a VHS movie through my TV, ALL I CAN SAY
IS, 352x240/288 is bullshit. I mean.. the resolution (or whatever you are
calling it today) don't look like no 352x240/288 !! The picture is much too
sharp to be x240/288 or perhaps coupled w/ something a little greater
than 352x

I was watching Jeepers Creappers and the picture quality of this
movie was great (on my 13" TV) Much too sharp to be so low in res.

Just like TV sets. I don't believe they are 352x240. They HAVE to be
something like 640x480 or 800x600.. give or take a few pixels. That, and
a few AR algorithems w/ frame or video size/resize ratio's..

If it weren't for the VHS noise level on those tapes (not capture card)
(still having trouble determining EXACTLY what is causing it) I think we
would be seeing something a little different.

A while back, I was THAT close to accomplishing a near duplicate of VHS
quality, and not no 352x240/288 either !! But, I had to stop, and now, I've
all but lost my place where I left off, and so, I don't feel it's worth it
anymores to continue that quest. But, at the time, it was a great
experiment (trial n error)

For those who have shopped at BJ's.. they have this 60" or great Widescreen
TV and I tell you, though I've seen many, that looked crummy, this one has
it perfect. I mean, I've seen many movies shown on this screen, and they
have this bench you can sit on, and watch. I tell you, if there was a WS tv,
that is the one I'd surely get. If I remember the model/make, I'll post back
here which one, so you all can get a look at what I'm talking about. I WANT
that WS set !! I tell you, there are movies that I DON'T like watching, but
when you sit (or stand) in front of it, say 6' or greater, you just fall in
love w/ the movie (any movie) That's the effect this WS set had (has) on
me !! I think it was plazma (thought they were bad though) I'll have to
verify tomorrow.

-vhelp

[SatStorm]

This convertation is one of the 3 - 4 subjects which all the time we return to. It's like the "CQ vs VBR" subject....

The problem is that people confuse resolution with framesize and skylines.

On VCD the framesize is 352 X 288/240. All the "lines" combine this framesize are active (they have info)
On VHS we have 2 fields which make one frame. The frame overall is 352 X 576/480 (officially, I'll explain later). But this is a trick: The frame has 2 fields, which they are in offset mode (zig zag order). Each field have 144 active and 144 non active skylines. If a skyline is inactive, then there is nothing. The phosphor of TV gonna keep a while the last info, and then gonna fade. But this never happens, after a while (3 filds later) a skyline gonna return to replace it, before it fades.
With media, we can't have "nothing". SO: We grabb the fields and the encoder later gonna delete the "nothing" info. So you end up with 352 x 288/240 lines. That's why Philips said: VCD is VHS like quality.

Over the years, filters and technics appear to make VHS look better. It is like filtering avis with virtualdub in realtime. The original info still is VHS, but with those technicks, the output gonna look better in our eyes
Again, here we have a problem: Encoders and our Eyes don't see the same way. So when you encode, you have to realise that you have VHS in front of you. You have to deactivate all your VCR filters (except TBC if you have one and NOT always), grabb and then add filters and stuff to make the mpeg output look nice. You can succeed that way picture almost equal the results your "state of the art" VCR can do from the same VHS tape, the analogue way.

And about posters, there are some specific ones in the forum, pops up once in a while just to create mess. A simply "search button" action, gonna show you easily who is who...

[House de Kris]

House de kris, I suggest you to take a swim before you post....

JVC is the creator of VHS and SVHS.
JVC said: VHS is 352 X 288/240 and SVHS is 352 X 576/480
The God spoken.

Anything else is bullshit.

If JVC is the creator of VHS, then what was the role of RCA (most notably; Triangle Park, NJ)? Hint, check into the relationship between RCA and JVC a couple decades ago.
If JVC is the creator of S-VHS, then why does every S-VHS machine sold have to pay a licensing fee to Faroudja?

If JVC really said what you claim they did, then please share with us your resource. Without it, this is just another baseless claim on the internet. Exactly the type of claim Shizuka's boss was trying to avoid.

Now, what is it exactly that makes me keep popping up with about this whole "VHS is equivalent to VCD" type of threads? It is when people claim VHS has only 240 horizontal lines (vertical resolution). BTW, to make it easier to write and read, I'll limit this to NTSC only, you can substitute 288 or 576 wherever appropriate. This simply (like that word, right?) is not the case. A VHS machine will record every horizontal line you give it. Vertical resolution is a low frequency phenomena and is not hard at all to obtain accurately and exactly. And no matter how many times you write to the contrary, or how many articles you plaster on the internet, this fact will not change. If you would like to 'simply' prove it to yourself, tape a show off the air, watch it live while you are taping. Then, play the tape back, and watch it. Is the playback any dimmer? If not, how can half the information be missing and not be dimmer? If this still does not convince you, then monitor the signal going into the VHS machine on a scope, verify both fields are there. Then playback a tape and monitor with a scope. Gosh darn, both fields are still there! VHS will give you 480 horizontal lines of active video. It is never something like '480 on a good day, but 320 for sure the rest of the time.'

Getting back to what you claim JVC says about S-VHS, raises more suspicions about the validity of your source. The improvement S-VHS brought over VHS is more vertical lines (horizontal resolution). This is achieved via a wider bandwidth recording. Your claimed JVC quote has the horizontal resolution being the same for VHS and S-VHS. Makes one wonder.

Which God is it that spoke anyway?

[You_Are_Alive]

Shizuka,

Your going to be in a world of hurt if you guys go ahead and just mix and match cameras. This is not how it should be done. They will all give you 1) different colors and 2) diff resolution. The Digital 8 may pass but the vhs camera, no way. Just try cutting between those images and the difference is between night and day, not just in terms of resolution but also color and how this color space will later also be seen on different TVs.

Even 2 camera's that are identical can give different colors. They must all be adjusted, either in camera menu itself or later in post production / editing your footage. The secret to pulling this off the easy way is to have consistency between all your shots. Hopefully identical cameras and on a tripod or stationary position, same lighting conditions, and tests to calibrate the camera's shooting environment which will take some preparation.

As far as resolution, I can point you to a site where the actual tests were done with accuracy and detail but are put in easy terms so ppl can understand what they are looking at.

Here are some real world measurements from a test setup since it seems that you're concerned mainly with resolution. Just remember that color and lighting will play a big role too, not just the resolutions. Prepare beforehand with some test shots and try to co-ordinate how the video should be shot at each site.

DV Resolution detail: about 540 lines
S-Video Resolution detail: about 480 lines
VHS Resolution detail: about 230 lines

More tips: Shoot with 2 cameras simultaneously, if possible. One with a tight close-up on subject's eyes, and another cam with a wide angle. If thats not possible, keep the camera as close as possible to get a better "quality" zoom on the eyes. Every NLE out there diffuses or softens and degrades image when you zoom in further, just like photos. This will be evident, and probably make it impossble to do with the vhs since low quality to begin with. There is software out there that can achieve this with much, much better precision then with a NLE, but you'd have to capture a still image and then render it out as a compressed or uncompressed .avi file. This will take alot more time. One such software that does this is MovingPicture. Or you can do Flash as well.

Okay, I'll stop here. PM me if you want more info.

[BJ_M]

S-VHS and Hi8 both use Faroudja technology - more so Hi8 ...

Faroudja didn't invent either though ....

JVC did invent VHS and D-VHS and S-VHS -- a quick search anywhere will confirm that .. there was a relationship w/ RCA at one time - but that doesnt bear weight on the facts ..

[SatStorm]

House de Kris, I suggest you again to go for a swim.

[Shizuka]

Hello,

First, I want to say "thank you" for all your advice. Sorry I could not be posting before now. Our office moved in the first of the month and things have been messy.

I still need printed source for information on these types of camera/media. I still do believe the dv tapes to be better. I can see when I watch them. The digital 8 site will convert to miniDV. We convinced them due to final/tape conversion problems, not quality issue. The VHS site does not respond to our requests at all. They say quality is same as our miniDV and it should not invalidate their part of the study. If we could have source, we might convince them of the problem.

Maybe it is my English. It seems like some of the posts were people being angry at themselves. Please do not be fighting on account of my question. If it is my English, my pardon, I am learning.

Shizuka