why is there some black bars after VHS capturing?

[anonymoustly]

When I start capturing VHS, I see a narrow black border on both sides. (there is no black border above and below)
16:9 to anomorph. But how is this possible?
Or is it that 4:3 anamorph is actually 768x576 pixels and not 720x576??
(my theory is that an actual 672x576 resolution is crammed in from the available 720x576.) That leaves you with 24 pixels on both sides.

[Bwaak]

The 702x576 part (but usually 704x576 part) is the content area, which can be 4:3 or 16:9. See https://en.m.wikipedia.org/wiki/Pixel_aspect_ratio

[jagabo]

In short, a little more than the active picture width is captured in case the source isn't centered perfectly.

[dellsam34]

Jagabo summarized all what I was about to post, so I just leave it at that.