Weird line at the top

Getting started with a Blackmagic product? Ask questions here about setup and installation.
  • Author
  • Message
Offline

Martin Johnsson

  • Posts: 2
  • Joined: Fri Jul 21, 2017 7:36 am

Weird line at the top

PostTue Jul 25, 2017 10:37 pm

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?
Attachments
20157204_10211791418053903_8399908774431339941_o.jpg
20157204_10211791418053903_8399908774431339941_o.jpg (138.62 KiB) Viewed 1924 times
Offline
User avatar

Massimiliano Celindano

  • Posts: 153
  • Joined: Sat May 09, 2015 5:03 pm
  • Location: Rome, Italy

Re: Weird line at the top

PostWed Aug 02, 2017 2:19 pm

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

Martin Johnsson

  • Posts: 2
  • Joined: Fri Jul 21, 2017 7:36 am

Re: Weird line at the top

PostSun Aug 06, 2017 9:36 am

So there is no way to avoid this?

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

Massimiliano Celindano

  • Posts: 153
  • Joined: Sat May 09, 2015 5:03 pm
  • Location: Rome, Italy

Re: Weird line at the top

PostTue Aug 08, 2017 2:05 pm

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

Colin Barrett

  • Posts: 603
  • Joined: Wed Dec 05, 2012 12:23 pm
  • Location: Milton Keynes, UK

Re: Weird line at the top

PostWed Aug 09, 2017 9:37 am

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.
Blackmagic Teranex 2D, Ultrastudio Express, Intensity Shuttle (Thunderbolt), Two H.264 Pro Recorders (Mac OSX) & lots of old VTRs used for digital archiving of legacy video formats for major libraries, broadcasters, universities and public archives.

Return to Getting Started

Who is online

Users browsing this forum: No registered users and 37 guests