The "capture window" effect and preferred adjustment

Author: Moth3r
Time: 3-Nov-2004 8:26 AM
Post link

As most of you will no doubt be aware, the majority of PC capture cards crop a small amount from the extreme left and right edges of the video image during capture (this is the "capture window").

If nothing is done about this then it can result in a small inaccuracy in the aspect ratio of the capture, i.e. if you only capture 2.30:1 and display it as 2.35:1 then the image will look slightly squashed.

The standard fix is to capture at a reduced horizontal resolution, e.g. 704 pixels, then add black borders 8 pixels wide either side to increase the image width up to the usual DVD-spec of 720 pixels. When displayed on a TV, these side borders are normally in the overscan part of the picture so are not noticeable. They can however be distracting if viewing on a PC.

If you are making an anamorphic version, then you have another option; capture at 720, but increase the vertical scale factor slightly to compensate for loss of the sides. By a quick calculation, I reckon the factor need to be increased from 1.33 to 1.36 (for a PAL capture, 327 vertical lines in the 4:3 source would normally increase to 436 after resizing to 16:9, but with the compensation it would be about 445).

So what's the vote? I am currently leaning towards the first option. Are side borders an issue to anyone? Would you prefer to see the full 720 pixels in use?

Guidelines for post content and general behaviour: read announcement here

Max. allowable image sizes in signatures: reminder here

Author: MeBeJedi
Time: 3-Nov-2004 8:41 AM
Post link

I capture at the full 720x480, and Vegas allows me to visual adjust how the image fits within the screen, so this isn't a problem for me.

MeBeJedi: Sadly, I believe the prequels are beyond repair.
JediRandy: They’re certainly beyond any repair you’re capable of making.

MeBeJedi: You aren’t one of us.
Go-Mer-Tonic: I can’t say I find that very disappointing.

JediRandy: I won’t suck as much as a fan edit.

Author: Spider
Time: 3-Nov-2004 8:08 PM
Post link

"Moth3r" I found the same thing with PC capture cards. I do have a Panasonic E80 DVD recorder that capture the image just right.