Blackmagic Forum

When I capture videos with my Blackmagic Intensity Shuttle Thunderbolt, the video appears a bit strange in the top. (look at the attached picture)

Only with composite and component, not if I use HDMI.

Is it something wrong with the device or is it just normal?

It's absolutely normal. You will notice the same pixelation even with HDMI but in another position.

So there is no way to avoid this?

Do I have to crop the captured video to make the top become "normal"?

As far as I know there's no way to avoid it. Cropping wil surely do the job, but I would not recommend it.

This is because, in an old-fashioned, standard definition, analogue TV world a frame of a TV picture was created by two interlaced scans of lines - alternatively odd lines (1,3,5,7,9 etc) and then a flyback to the top halfway point to fill in the even lines (2,4,6,8,10 etc). Each scan set is called a "field" with two interlaced fields producing a full frame with either 25 (PAL, SECAM) or 30 (NTSC) frames produced per second.

So........... the step at the top of a digitised frame is displaying the half-line scan start-point of the second field in the whole frame sequence. On an old-fashioned CRT TV screen all this is outside the normal picture display area (known as "overscan") but of course when you're creating a digitised recording from the analogue source you see everything.

I'm currently digitising to ProRes422 a load of material from a pile of professional-quality NTSC Hi-8 recordings and lots of this stuff becomes apparent (top and bottom) when viewing on a 4:3 CRT monitor in "under scan" mode.