HDV's Rectangular Pixels

Posted on by Larry

[ This article was first published in the September, 2008, issue of
Larry’s Final Cut Pro Newsletter. Click here to subscribe. ]


Leo Diaz writes:

I have my settings right in Final Cut Pro, I believe. However I have a question.


In the easy setup the output video for HDV is 1440 X 1080 60i. But when I Make a QuickTime movie the dimensions show 1920 X 1080. Is there something funny here? Or is this right.


There also seems to be some good interlacing in the video when shown could this be the reason?

Larry replies: Leo, thanks for the question.

You have two different issues here.

Issue 1 – HDV

HDV uses rectangular pixels to represent its image. Each pixel is short and fat, which means it only needs 1440 pixels to represent an entire line of HD video.

However, the computer (and some other video formats) use square pixels to represent the image. So, when you export from HDV to a QuickTime movie, Final Cut converts the pixels from rectangles to squares. Because the square pixels aren’t as wide as the HDV pixels, it takes more of them to create the image, which is where the 1920 pixels come from.

In other words, 1440 short, fat HDV pixels equals 1920 square computer pixels. Everything is operating normally.

Here’s an article that might help explain this further.

Issue 2 – Interlacing

By default, Final Cut Pro does not show interlacing; unless the image is displayed in either the Canvas or the Browser at 100% size.

However, QuickTime isn’t so obliging. It always displays interlacing. And, because it opens the image at full-size, unlike Final Cut, which tends to scale the image down in the Canvas or Viewer, the interlacing is all the more noticeable.

Here’s the basic rule. Leave interlacing alone if you are going to DVD or broadcast. Remove interlacing if you are going to the web. This often means you need to create two different versions of your program, one with interlacing and one without.

Here’s an article that can help explain interlacing further.


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