[ This article was first published in the December, 2008, issue of
Larry’s Final Cut Pro Newsletter. Click here to subscribe. ]
Denny Goodrich, from Iowa State University, writes:
We are shooting DV and in FCP I am using a DV timeline. The Media 100 would be 720×486. We noticed that whenever we encoded something for web there would always be little black bars on each side. After getting clued in to this, I notice that there are, indeed, very narrow black bars left and right. Why should this be? The material I get from the Media 100 are QuickTime movies that have been cropped to 720×480, but these black bars appear here, too. Our current work around is to blow everything up to 102-percent, but I really don’t like to do this.
Larry replies: Denny, please, for the love of humanity, DON’T enlarge your video image past 100%. That’s just wrong!
Those black bars called, I believe, horizontal blanking, are a part of every DV frame. It is designed to allow the electron beam in a CRT to switch from one side of the picture tube to the other.
If you want to get rid of them, crop your image 2-3% during compression. Or leave them alone. You’ll never see them on a TV set and most people won’t notice on video posted to the web.
But get rid of them during compression, not by enlarging your image during editing.
UPDATE – Dec. 21
Uli Plank adds:
While enlarging vertically would be wrong (and very bad in case of interlaced video), enlarging horizontally only is correct for square pixel displays.
You are right about blanking, and digital video is meant to be 702 pixels wide (plus 9 pixels of blanking on both sides). This size will contain the full 4 by 3 or 16 by 9 image! TVs take this into consideration.
So, if you crop, your image will be ever so slightly squeezed from the sides on square pixel displays. Adobe has changed it’s attitude towards this issue recently (check out AE in CS4), while Apple still insists on digital video being 720 pixels wide…
Larry replies: Thanks, Uli. Except, if the cropping is done during compression and you take the revised dimensions into account for your final image size, the web will display it properly. Clearly, you would never crop if your goal was to put the material on a DVD or broadcast.
