Digitizing Video

In an ideal world, you have complete control over your video shoot. You’re shooting in digital, using the best equipment available. But what about working with older content, shot on analog formats like VHS, Beta SP, or UMatic? There’s a lot of great archival content out there, and just because it’s not digital doesn’t mean it’s not valuable.

It is not, however, always easy to digitize older content. Ingesting analog video to digital is a delicate process, particularly when the original has high levels of noise. The more noise, the greater the bit rate required to compress it. Common problems include sync artifacts, edge artifacts, and interlacing. All of these, if you leave them alone, will increase your bit rate and make your video appear less professional. Let's take a look at these nuisances and how to correct them.

Note: Make sure to use the proper setting for the field dominance of your hardware.

Recognize and Fix Sync Artifacts

You may see three kinds of sync artifacts during digitization: vertical, horizontal, and tracking.

Vertical sync artifacts will appear as intermittently dropped frames or fields that create a strobing effect. This problem is caused by the mechanical limitations of video tape, particularly with older archival formats, and is best resolved by using a Timebase Corrector to resynchronize the signal. If your playback equipment cannot support a TBC, as is the case for most consumer VCRs, a Frame Synchronizer may be the only option. Take a look at the movie below for an example of Vertical sync problems:

Sample Movie 1: Vertical sync artifacts.

Horizontal sync artifacts are harder to solve. They appear as shifting horizontal lines in the video signal, and are probably due to a defect in the tape or playback equipment. The best solution is to try the ingest on a higher-quality playback device. If you don’t have the budget for that, you may have to clean these up frame by frame.

Tracking artifacts vary in seriousness. Minor tracking errors will cause small glitches, usually near the bottom of the image. Adjusting the tracking on the playback device sometimes fixes these. If not, crop them out of the picture in editing. If you see tracking errors that aren’t at the bottom of the image, clean your playback heads or try another playback device. Do the best you can, because you won’t be able to fix them later.

Figure 1: This minor tracking problem can be cropped out.

Figure 2: If your tracking looks this bad, fix it before you digitize.

Crop Edge Artifacts

Due to the limitations of analog video tape, color banding may occur near the sides of an image. Banding may not appear on TVs because it is outside the "action-safe" area of the display and so is hidden by overscan. It’s best to watch your content on a computer monitor to check the edges.

Figure 3: Edge artifacts outside action-safe area, from analog ingest.

The green cast visible on the left margin of this captured still is an edge artifact. If possible, crop these bands out of your video after scaling. If you are creating new content without garbage image data on the borders, don't crop the sides.

Back to the Video Compression Main Article.

Posted: 2008-08-21