Best VHS capture resolution??

[lordsmurf]

BT8x8 captures at something like 688x486
It's nowhere even remotely close to 1400.

[junkmalle]

If you search through the forums for "btwincap" you'll see lots of people talking about capturing at 712x480. Unfortunately that's not a DVD compliant frame size so you have to stretch/shrink or pad/crop for DVD.

Here's a big long thread with lots of talk about BT8x8 captures:

https://www.videohelp.com/forum/viewtopic.php?t=199669

[Nelson37]

I'm pretty sure that the original test subject card for this information was either a Leadtek or a Winfast card, which use the BTxx chipset, SFAIK.
I am pretty sure it was Trevlac who did the original research, and he definitely seemed to know his stuff.

Trial and error will NOT tell you the native resolution, but it WILL tell you which capture resolution looks best.

The point is that you the user have NO CONTROL over what that original resolution is, what resize method is used, and what filters may be applied. Those decisions are made FOR you, by the card.

The effect of these manipulations is unknown, because the extent of the manipulations themselves is unknown.

What really pisses me off is that in spite of this information, for over two years many people who claim a level of expertise in this field will still insist that 352x480 capture is best for VHS because it best matches the apparent resolution of VHS. When the factual data absolutely DICTATES that a 352x480 capture, for most cards, is just NOT POSSIBLE.

For a card which is native at 720x480, like an ATI for instance, it may very well be that the internal resize to 352 works fairly well. ( My visual tests say otherwise) BUT, the resize DOES occur, and I find it difficult to believe that with a software resize, with which many methods and settings are available, there would not be at least one that is significantly superior to the card's internal resize, for which there are NO selectable methods or settings.

Give me control and I will find a better way. Take control away from me and I will not know that a better way is possible.

[ForYouAndI.com]

"Give me control and I will find a better way. Take control away from me and I will not know that a better way is possible."

My thoughts EXACTLY!

[junkmalle]

BT8x8 captures at something like 688x486
It's nowhere even remotely close to 1400.

OK, it samples internally at 1400+. It then crops and scales depending on how the driver programs the chip. It looks like the BTWinCap drivers give the best results at 712x480.

http://www.conexant.com/servlets/DownloadServlet/100600B.pdf?FileId=443

[ForYouAndI.com]

I looked through that thread and a few tutorials on how to capture VHS with VirtualDub but none of them mention which driver to choose
WDM Image Capture (VFW)
or
Conexant's BtPCI Capture (DirectShow)

[junkmalle]

Use WDM unless you're using software that only works with VFW. VFW is old and deprecated by Microsoft.

[ForYouAndI.com]

I'm using VirtualDub on WinXP pro. I'm a little confused. For the same device I see both WDM and VFW:

WDM Image Capture (VFW)

Is that the correct one?

[junkmalle]

I'm using VirtualDub on WinXP pro. I'm a little confused. For the same device I see both WDM and VFW:

WDM Image Capture (VFW)

Is that the correct one?

VirtualDub can only capture via VFW. What you're seeing is the WDM driver with a VFW wrapper -- ie, a WDM driver massaged to look like VFW. Not as good as directly using a WDM driver but that's your only choice with VirtualDub.

[ForYouAndI.com]

What do you mean it is not as good? I know it uses more cpu but but my computer easily handles it. My concern is quality. Does it affect quality? In other words, will VirtualVCR give me better quality?

[junkmalle]

What do you mean it is not as good? I know it uses more cpu but but my computer easily handles it. My concern is quality. Does it affect quality? In other words, will VirtualVCR give me better quality?

The picture quality may be the same. It's mostly a matter of CPU usage -- and the higher probability of dropping frames as CPU usage goes up. Also, the VFW wrapper may not give you access to all the card's features.

[anitract]

For a card which is native at 720x480, like an ATI for instance...

I thought the native resolution of ATI AIWs was 704x480. Where are you getting 720 from?

[Nelson37]

Well, the real answer is that it is not either one of those, precisely. IIRC it was something like 688x468, but that is a vague recollection.

I often use 720x480 and 704x480 interchangeably, yes they are different but some recent testing performed by others here indicates that a DVD player will handle both exactly the same.

The concept was that for a card whose native res is close to 704x480, the internal resize may well give decent results.

BUT, the entire THEORETICAL basis for the statement that the best capture res for VHS would be 352x480 is based on the capture res MATCHING that of the source. A capture to a higher res which is then resized to 352x480 blows that whole theoretical argument out of the water.

I've been making this argument for OVER 2 YEARS. All this BS about Nyquist theorem, oversampling, yadda, yadda, yadda, is just so much meaningless babble.

[davideck]

The consensus on this thread seems to be that the actual comparison tests performed demonstrate that capturing at a higher resolution looks better.

Has anyone done a comparison test that suggests otherwise? On what hardware?

[lordsmurf]

Has anyone done a comparison test that suggests otherwise? On what hardware?

I did comparison tests about 2 years ago on ATI Theatre, BT8x8 and LSI (DVD recorder) chips. The ATI AIW was pretty much indistinguishable between 704 and 352 on like sources. There were actually some aliasing artifacts upsizing to 720x480.

The LSI was "softer" at 352 than 720 (if I get really anal), but both were sharper than DV streams, ATI, BT8x8, and a couple others. That was likely just the way that machine was used, the LSI in the JVC performs pretty much equal at both (meaing the 720 was artificially enhanced, which is a problem or "problem" on some cards/devices).

The BT8x8 was a bitch. You had to tweak the drivers, the internal filters, and then capture at this odd-ass resolution to avoid noise/artifacts, as well as aspect ratio errors. Anything above the native (meaning max of 768x576 or 720x480) looked fine, but anything below was just butchered. You then had to pad the sides to restore aspect, change to a better resolution in a good encoder, lanzscos resize, avisynth everywhere, and encode away.

I know I still have the images. But not sure "where" they are, exactly. Likely on an old backup, as I had a hard drive crash that wiped out a bunch of my C: drive in May 2004. These tests were done some months before that. Some of them were on this site, but the server crash last year purged a huge number of images from the forum (including avatars), and they were lost from posts here.

There were some DV tests there too, but lost those as well. Included Canopus, Matrox and one other from a camera pass-through. I've never had the time to go re-do these tests, it tooks several weeks at the time.

[davideck]

The ATI AIW was pretty much indistinguishable between 704 and 352 on like sources. There were actually some aliasing artifacts upsizing to 720x480.

Doesn't that suggest a flaw in the ATI cards?
If alias artifacts are caused by upsizing to 720,
what are you supposed to do with SVHS or Hi8 sources?

[ForYouAndI.com]

Good point, davideck.

[junkmalle]

The ATI AIW was pretty much indistinguishable between 704 and 352 on like sources. There were actually some aliasing artifacts upsizing to 720x480.

Doesn't that suggest a flaw in the ATI cards?
If alias artifacts are caused by upsizing to 720,
what are you supposed to do with SVHS or Hi8 sources?

Capture them at 704x480?

[davideck]

Capture them at 704x480?

But why not at 352 if;

The ATI AIW was pretty much indistinguishable between 704 and 352 on like sources.

Or were you just talking about VHS resolution, lordsmurf?

[lordsmurf]

Aliasing is an inherent flaw of partial resizing digitally of any image. It's often very subtle, but it exists. Even tv broadcasts and satellite streams can have this effect. Going from a native 704 up to something like 720 is going to have an alias effect, regardless of how "advanced" the hardware or software. Even moreso than a downsize, in fact. Plus downsizing is easier to accomplish than upsizing.

[davideck]

So for ATI cards;
Capturing at 704 is better than 720. That makes sense.
Is capturing at 704 better than 352 for SVHS, Hi8, etc.?

[lordsmurf]

S-VHS, it's up to you. Those are "either way" sorts of sources. And it all depends on the original source. If it was shot at S-VHS, then go higher. If it was from a low signal and merely recorded on S-VHS to retain full quality, then go a little lower (likely still higher than the source). I do both ways.

[thecoalman]

Since your selected resolution DOES effect the ultimate bitrate you choose, it DOES effect the length of the video indirectly. What am I missing?

Your not missing anything. What you said is correct but effective bitrates for different resolutions can overlap. I was just trying to make the point that it's the bitrate that determines file size, the resolution has no affect on it.

[SatStorm]

Let me jump on this....

For various reasons capturing at the highest framesize your capture card can, is at the same time the best you can do and a huge overkill.

Many users wondered why we need to capture at those overkilled framesizes while officially, VHS is just 352 x 288 / 240 and SVHS is just 352 x 576/480 (actually close to those framesizes, not exactly those framesizes).
At the same time other users start wondering what their capture card actually do... How a capture card captures? Is there any internal variebles we need to know of?

At the same time, cheap DVD standalones became a mainstream reality: those DVD standalones plays anything you through on them but not at the best possible way: Actually, the decoding mpeg 2 parts they have inside, are the most low budget ones that exist!

Combine all those elements together, and you end up with countless conversations about those subjects

My opinion about the subject (and I won't analyse it, just take it as is, if you care)

VHS is indeed ~ 352 x 288/240
SVHS is indeed ~352 x 576/480

When we capture VHS / SVHS we capture the higher we can. That way we have a 97% of the picture quality our capture card can offer.
If we want the 100%, then welcome to Hell: Search tons of technical info, to discover what the native framesize of your card is, proper resize, do voodoo stuff with it and get the 100%. For me: A waste of time (especially for VHS tapes....)

Now: depending the DVD standalone we have or we choose of how to encode:
Cheap / maistream standalones gonna show 704 x 576 / 480 far better than 352 x 576 / 480
Better standalones / Hi Fi / Hi End models, gonna show 352 x 576/480 as really is.

Because the average user own a cheap standalone, we end up using 704 x 576/480. That way anything shows as it has to

Personally, I convert VHS tapes to 352 x 288 interlaced (yeap, possible for us, the PAL users) and the picture looks identical the VHS tape on a plasma / LCD screen. But I use a hi-end DVD standalone player for this, not a cheap one.
At the same time, I convert SVHS to 352 x 576 interlaced and also look identical the original tape.

When I playback the same those DVDs with a cheap standalone on a typical TV, they original tapes look far better

What that tells me? There is nothing wrong with the convertion or the framesizes. The problem is elsewhere, but the average Joe won't understand even if I try to explain it. So, keep your projects for yourself in the proper way and give to the average joe the standard solution: Capture and encode VHS at 720 x 576/480 if possible!!! (like those quality awfull hauppauge win tv pvr cards do). Everybody is happy that way, except you, who knows the truth...

[davideck]

VHS is indeed ~ 352 x 288/240
SVHS is indeed ~352 x 576/480

You're claiming that SVHS has the same Horizontal resolution, but a higher Vertical resolution than VHS? You've got that backwards...

Capture and encode VHS at 720 x 576/480 if possible!!! (like those quality awfull hauppauge win tv pvr cards do). Everybody is happy that way, except you, who knows the truth...

Are you suggesting that the Hauppauge cards are good or bad?

[lordsmurf]

VHS is indeed ~ 352 x 288/240
SVHS is indeed ~352 x 576/480

You're claiming that SVHS has the same Horizontal resolution, but a higher Vertical resolution than VHS? You've got that backwards...

Yeah, he's got it backwards.
VHS is about 250-300x480
S-VHS is about 400-500x480

But the rest of his argument is surely valid. Overkill is overkill.

Many times the "my 720 looks sharper" is merely due to artifical sharpening by the resizers of the card. The source was not really that sharp, and whether the card's sharpen job was good is a topic of much debate. Those cheap cards, no, not at all. Your more expensive cards, maybe. But then you have to consider most expensive cards are not crap and therefore do not need such filters to begin with.

The x480 is so you can grab both fields. The resolution axis is actually a bit less than that in analog, but you cannot interlace it with conventional methods at anything less. Well, not really. Complicated.

[davideck]

Yeah, he's got it backwards.
VHS is about 250-300x480
S-VHS is about 400-500x480

But the rest of his argument is surely valid. Overkill is overkill.

720 is hardly overkill for SVHS.

Those who have posted actual comparison results on this thread seem to be claiming that 720 looks better than 352 even for VHS. That doesn't sound like overkill to me.

Many times the "my 720 looks sharper" is merely due to artifical sharpening by the resizers of the card.

My experience is that 352 looks softer than the original. Particularly with SVHS. 720 is noticeably more transparent.

[anitract]

I'm gonna agree with davideck. With my AIW captures, 704 looks scads better than 352 when viewed on a TV. Actually, IMO, 352 looks worse (softer) than the source, whereas 704 is much closer. In my mind this is due to AIW handling its native format in a more efficient manner...

[ForYouAndI.com]

Why didn't the hardware programmers program the native resolution that the card captures at, so that capturing programs could easily get it?

[lordsmurf]

720 is hardly overkill for SVHS.

I already agreed to that earlier. But it can go both ways. It depends on the earlier generation of source (recording off tv, backup of VHS tape, etc). Or if S-VHS is the source.

I think satstorm was using S-VHS as a comparitive mostly, the root argument was VHS captures are not given benefit by upsizing falsely. Overkill.

Many people that "see advantages" are often psychologically fooled by bigger numbers, or have a card that falsely sharpens in the internal filter system. At least when discussing lower resolution sources, like VHS and much of tv sources.

It's all about the source and the hardware in use. Nothing magic about it. It's all very basic stuff.

DVD players are also a key ingredient, some of the MPEG playback chips suck, much like the capture chips do. You don't need a $2000 unit like a certain troll on another forum blabs about, but a $100-200 player is generally a bit better than the $30 Walmart special or the whiz-bang "play anything" Philips and the likes.