Interlacing is often found on content originally created for display on a television, as opposed to a digital device. This type of footage is created by running “half frames” at twice the frame rate by drawing every other line and then filling in the remaining lines on a second pass. On a digital screen, both frames must be combined and displayed at the same time. This results in noticeable lines in footage that are particularly bad when there is motion in the video.
There are several methods available to de-interlace content, each with their own benefits, but the recommendation is to correct the interlaced footage as early in the production process as possible to ensure the highest quality. Due to how the de-interlacing process works, it is very important that it is done before applying additional modifications such as frame scaling. Attempting to de-interlace footage that has been modified from its original state produces noticeably bad results.