black/blank area on either sides of screen

[3390]

i just transferred a video from tape to my comp thru an adaptec capture card.. and when i played it back on the comp, there is a black strip of about 1/4 wide on either side of the video. sometimes it is on one side, sometimes on both sides. why is that and how can it be corrected? thanks

[edDV]

It is there because of H-position variability back in the mid 1980's over broadcast transmission. Various transmission or recording issues caused up to (rarely) an 8 pixel shift. More likely 0-2 H pixels.

TV is broadcast at 4:3 which is 704x480/576. They added 8 pixels left and right to protect for H shift.

That is how 704 became 720x480/576.

If you cap 704x480x576 you get the real 4:3 central image. If you cap 720x480/576 you get 8 black pixels on the left and right.