Deartifacting

One of the great new features of Primatte Keyer Pro 4 in Avid is the Deartifacting filters, which are designed to assist you when performing a key on source footage from DV or HD cameras by removing any blocking around the edges of the image caused by the compression algorithms in the source format. The Deartifacting filters are built around Red Giant Software’s Prekey™ technology.

Overview

In the film world footage is shot on film and scanned into uncompressed RGB image sequences at 8-bit or greater color depth. With footage shot on video, however, the output is usually compressed, and saved in reduced 4:2:2 or 4:1:1 YUV color space. This compression and reduced color depth can often cause problems when keying objects with soft edges, such as hair or smoke, or on objects with a great deal of motion blur. Primatte’s Deartifacting controls allow you to get a superior key by pre-processing the image with algorithms specifically designed to address this issue.

Consider this example. The image below shows an actress in front of a bluescreen. The footage was shot on HDV.

Below is the same footage with an initial sample done. If you look along the edges of the actress’ face you can see blocking and artifacting caused by the compression in the DV source.

The image below shows this same footage with a standard Primatte Key applied without using the Deartifacting tools.

The image below is the exact same key with Deartifacting enabled. Once Primatte pulls its key the blocking and artifacting becomes quite noticeable. With the Deartifacting filter enabled, you’ll see a remarkable difference in the smoothness of the edges in the keyed output.

Interface

The interface for the Deartifacting controls is quite simple, comprised of a pop-up menu and a slider.

The Mode pop-up contains four values:

• None

• DV/HDV

• HDCAM

• Other

As their names suggest, you should choose DV/HDV for any footage shot on a DV camera, and HDCAM for HD video. Other is for when you have footage that comes from a video format not previously mentioned, or on any footage that has these types of blocking issues, no matter what its source. Primatte Keyer will then analyze the footage and make its best guess as to how to smooth the edges.

Strength is a simple value slider to determine how much image correction is applied to the image. It ranges from 0-100%, and defaults to 100%.

From a workflow standpoint, Deartifacting is a pre-process. In the internal workflow these algorithms are applied to the image before it is keyed. However, if you pull a key and subsequently notice that there are jagged edges on your objects, you can go back afterwards and apply the Deartifacting controls after you have done your key, or at any other point in the process.