April 17, 2009

Wider aspect: directional content adaptive scaling

Future video-oriented versions of Content Aware Scaling might eliminate the need for "directional content aware scaling," if the problems encountered in scaling video can be solved.

It seems that the Food Network, HGTV, and other HD channels sometimes use a lens adapter or other technique to stretch SD content to HD. You can especially see the scaling in pans, where the center holds but the sides are stretched.

A post on the FCP-List mentioned that Teranex conversion and conditioning hardware executes a "center spread." Teranex (at NAB 2009, Booth SU5025) calls it "directional content adaptive scaling" and explains:

"Working with Turner Networks, Teranex developed a method of aspect ratio conversion using a non-linear anamorphic function. This technique, named FlexView, performs its aspect ratio conversion by leaving the picture information in the center of the image relatively undisturbed and then applies progressively more ‘stretch’ to the image as it gets closer to the edges. This process, while largely done in the horizontal domain also has a vertical component to help maintain correct geometry.

The basic premise is that most of the important content in a scene (the material that your eye is drawn to) is in the center of an image and the information on the edges is generally less important. Flexview leaves the center portion undisturbed and stretches the image most aggressively around the edges where there is less important material."

For more on this see the Flexview Application Note from Teranex.

You can do this right now with a free Final Cut filter (via The Editblog) from Andy Mees called Andy’s Elastic Aspect

And it seems like you might do this without too much trouble in After Effects or Premiere Pro with an appropriate gradient and a Displacement filter. Premiere with CUDA has better scaling quality, but the drawback is that the lower quality algorithms in popular software are unlikely to measure up to patented multipurpose hardware like Blackmagic Teranex.

For other options, see the nice thread on Creative Cow.

Note: It might even be possible to use the Protect options in Content Aware Scaling in later versions of Photoshop.

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