verical 4px black bars in video captured with a usb capture stick

[codemaster]

I used a usb capture stick and PowerDirector 9 to record video from an LCD TV. In PowerDirector, the settings for recording are: mpeg2 and "DVDHQ" profile. The recordings produced by PowerDirector are MPEG files, with MPEG2 video. The MPEG files have these properties: 720x576 px, 25 fps, interlaced.

All the MPEG files produced by PowerDirector from this capture stick, contain a vertical black bar on the left which has a width of 8 or 9 pixels, and a vertical black bar on the right which has a width of 8 or 9 pixels.

These black bars do not appear on the TV screen. This means that either the capture stick adds them, or PowerDirector adds them.

I already have a solution, I just add "crop(8, 0, -8, 0)" to the AviSynth script, but my question is: why are these black bars added?

[jagabo]

The bars are normal. With a standard ITU SD PAL 720x576 video capture the picture is contained in a ~702x576 frame. The capture device captures 720 pixels wide in case the picture/cap is off-center. So you end up with black bars at the left and/or right edges. You don't see the black bars on TV because the TV overscans the picture.

https://en.wikipedia.org/wiki/Overscan