VHS-->DVD + Overscan . . . Why Is It Okay on VHS?

[brijem]

Hello Everyone . . . this is my first post here.

I know this forum is probably loaded with questions about overscan, but I've run into a
odd situation concerning it where I haven't been able to find an answer . . .

I'm transferring an old VHS tape to DVD; at the opening of the tape there is an interview
with a text subtitle near the bottom of the screen - if I watch this tape on my VCR the title
resides in a safe location and is completely visable, but, once I import the video to digital
(into Vegas) this text falls outside the text safe area & into the overscan area. What I don't
understand (and would like to) is what sort of rule applies that can make this so - I import
video at 720X480. I'm not sure how the VCR is able to display this text safely - I assumed
overscan applied to any source . . . I understand the methods I can use to bring the text to
the safe area (of course I end up with a black "frame" if I view the resulting file on my computer)
and I don't question that - I'm just curious about how it can work on the VCR but be in need
of change once it's digital.

Could anyone explain?

Thanks : )

[lordsmurf]

The "safe area" in many programs is very aggressive, to keep you from going to close to the actual overscan borders (or rather, the average borders -- none are the same size, often ranges from 4-10%, so 7% on average).

Some programs have two "safe" outlines. One is the overscan border, the other is the "text area".

[guns1inger]

The Action Safe (outer border) and Title Safe (inner border) are often set at 10 and 20% respectively. As lordsmurf pointed out, this is pretty aggressive for most modern TVs. In Vegas you can modify this to better suit your needs. Options -> Preferences -> Video tab.

[brijem]

Well, I'm not really using the program guides (though I do have them turned on) - instead I monitor
output through a Panasonic BT-S1360Y pro video monitor (w/ overscan / underscan switching) & also render / burn small clips to refrence on a couple DVD players & televisions I have around & the result is the same . . . if I play the VHS tape to any of these TVs (or directly to the video monitor) the text is in a reasonable area, but as soon as
it's converted to digital it falls into an unsafe area - this is at 720X480 . . . . it makes me wonder if
the resolution is correct - I simply use the NTSC default template when starting a Vegas project.

[jagabo]

There's nothing wrong with the way you're capturing and making DVDS.

The reason TVs overscan is because it was difficult to keep the image the same size, centered and linear on old analog televisions. These would vary from set to set and even on a single set depending on the temperature, how long the TV was on, the set's age, etc. Having the TV draw a picture that was 10 to 20 percent larger than the viewable portion of the screen meant that small errors in size and postion wouldn't result in the edge of the frame being visible and linearity problems would be less noticable. This is much less of a problem with newer CRT TVs.

As others have pointed out, the "safe" guides that software uses indicate what should be safe on almost all TVs. If you were and advertizer and you found that 30 percent of the audience couldn't see the phone number in your ad you'd be pissed off!

[jman98]

In addition to jagabo's explanation, it's also possible for there to be garbage in the TV signal at the very outer edges and nobody wants to deal with angry customers complaining about how their TVs are "broken" when in fact the TVs are fine and it's the signal that has the problem. Overscan eliminates this potential problem.

[brijem]

Thanks everyone, I understand the reason & unfortunate reality of overscan, but what I still don't understand is why I don't encounter the subtitle cut-off when I play the video directly from the source VHS tape . . .

The VHS video does extend beyond the viewable area when played directly to my video monitor (I've checked it by toggling overscan & underscan on the monitor) and the same occurs on any TV I've played the tape directly to . . . but not so much that the subtitle is outside of the viewable area (in fact there is a good inch of viewable area below it when viewed directly) . . . here's what is confusing . . . after I capture the video, the same subtitle (that is visable direct from tape) is falling halfway into the overscan area & so I've had to resize the video to accomodate. I don't mind working around the overscan if the material requires it, but I don't understand why the subtitle in the original source is in an area that is still text safe and why, after converting the exact same material to digital, the overscan has changed dramatically enough to make the subtitle "fall off" the bottom of the screen.

It would seem to me that the rules would be the same for VHS and for the digital capture, and if the capture was indeed direct & unaltered that the resulting video would fall in the exact same place onscreen as it does when played direct from VHS; yet . . .

[jagabo]

what I still don't understand is why I don't encounter the subtitle cut-off when I play the video directly from the source VHS tape . . .

Because TVs vary in the amount of overscan. The safe region marked by software indicates a worst case overscan, not the average. Burn your video to DVD and you'll see each TV overscans the same with the DVD and VHS tape.

[brijem]

"Burn your video to DVD and you'll see each TV overscans the same with the DVD and VHS tape".

That's what I would expect, but it's precisely what's not happening, hense my question.

I'm not using the sofware as a guideline for the overscan . . . I'm playing the VHS tape directly to two sources to monitor / judge overscan - I've tried it on my TV & also on my Panasonic video monitor - in both cases the subtitle is in an acceptable area - I mainly use the video monitor for refrence & alternately the TV for a "second opinion". When I burn the captured video to DVD (or even before, if I monitor it on my video monitor) the resulting subtitle placement is quite different than it is directly viewed from tape - it falls lower than it does direct from VHS & low enough to be outside the viewable area, whereas it's fine when played directly from the VCR to the video monitor or TV.

[jagabo]

It sounds like your software is doing something to the video then. Maybe it's cropping off noise and/or black borders around the edge of the frame and resizing back up to 720x480. Or maybe the aspect ratio settings are wrong so it's scaling the image. Or maybe your TV(s) overscan different inputs differently (composite vs HMDI for example -- although your Panasonic monitor doesn't seem to have HDMI).

[cd090580]

it's strange, it should work fine, if you capture the file, you also capture the overscan from the vhs.

As jagabo said, your program probably cuts the vhs overscan but forget to add it back.

[brijem]

I was just trying again - I re-captured the segment and dropped the clip into a new
project, exactly as before - except, this time I used square pixels instead of 0.9091
(NTSC DV) - this worked perfectly. I'm fairly new to video . . . I've done a lot of work
in print & web graphics + have a fairly large recording studio so I'm used to standards
and so on, but video is a new realm for me and I'm curious if there would be any ill
effect to using square pixels when my destination is DVD. At any rate, the overscan is
now equal on both the VHS tape output and the imported, converted media!

Thanks again to everyone for their help and ideas!

[lordsmurf]

What device, what capture software?

[brijem]

Hi lordsmurf . . .

The source is a JVC HR-S4800U VCR, composite (I have the option for S-Video but I keep running into audio issues when I try to use it - but that's a whole other topic all-together) - the converter is a Canopus ADVC110 (input and output - it also feeds my video monitor for previews) and I'm using Sony Vegas Pro 8.0b - actually (and more specifically) I'm using Sony Video Capture 6.0e (the built-in capture program within Vegas).

[lordsmurf]

Use WinDV to capture. I bet Vegas is fubar'ing your video input.

[brijem]

I did have sucess, but not after much tweaking . . . thanks for the tip, I'll try WinDV & see if it might get it "right" from the start without the hours of messing about I had to undergo to get the Vegas capture into workable condition!