NTSC "Overscan"?

[heavydan]

Do NTSC TV's chop a certain area of the outside of the picture by a certain amount.

If so does anyone know how many lines top/bottom/left/right are chopped.

Here is what I have worked out for PAL TV's:
Set output video resolution to PAL 352x288
then go to the clip frame/arrange setting
type in 324x266
This puts a border around the video of 14 lines left, 14 lines right, 11 lines top, and 11 lines bottom.
You don't see the borders on the tv set, it is just to bring all the *real* picture into view.

Thanks all.

[cbear]

I just got an ADS instant DVD external capture unit. It states that it only captures at 704 X 480, because the rest is wasted on overscan.

[homerpez]

This could get really complicated... I wondered this myself, what I could figure on for overscan, or should I just guess...

To answer you, yes NTSC does have overscan, I just don't know what it is...

Maybe there's some calculation you can apply to the vertical number, and horizontal number... it must be a certain ratio...

I capped something at 480x480 res... it was off a videotape, so I got a thick slanted line of distortion at the bottom of the capture (turns out it was in the invisivble "overscan" area)... not knowing, I cropped the frame to cut off this line. Then I played it back on my TV. BIIIG mistake. If I knew the number of pixels I could block out in overscan, I could have "masked" it to hide that line, vs. making the whole frame too big! (Why mask? So I wouldn't have to waste bitrate encoding that dancing line)!

Maybe someone made a calculator someplace, but I haven't seen one...

<font size=-1>[ This Message was edited by: homerpez on 2001-12-16 23:29:37 ]</font>

[heavydan]

Thanks homerpez for your input.

I have some test mpegs which have a white screen with black lines for rows and columns creating squares then it has a bright red border signifing the overscan area. These are about a second long each.

These are setup like this for NTSC:
Set output video resolution to NTSC 352x240
then under the clip frame/arrange setting I have created the different sizes of 318x216, 320x218, 324x220, 326x222, 330x224, 352x240.

If anyone would like to help me out by putting them onto a cd-rw and testing them on your NTSC tv to find which numbers best fit the entire white squares on screen without the red border. Then tell me and I'll send you the test mpgs via email. The 6 VCD standard mpeg1's total 300KB.

<font size=-1>[ This Message was edited by: heavydan on 2001-12-17 05:31:24 ]</font>

[Truman]

TV overscan area is varying at different TV sets.
Average frame sizes are 320x218 (VCD)resp. 448x458(SVCD).

[heavydan]

Thankyou, Truman.