Noise & Artifact Reduction

2.1 Random Noise

In video, "noise" refers to the random, colored dots that appear to be overlaid onto an image. These dots give the image a grainy or, if severe enough, snowy appearance. The noise can be caused by video processing or by electromagnetic interference (EMI) picked up during signal transmission. The tests in this chapter have had different levels of noise deliberately added to the test images in order to assess the video processor's temporal noise reduction capability. While the Sailboat test has only a low level of noise in the water, the Flower test has had a medium amount of noise added to the background. Both the Sunrise and Harbor Night tests have had a heavy level of noise added. Although the four tests in this chapter have all had different amounts of noise added to them, they are all evaluated using the same scoring criteria.

2.2 Compression Artifacts

Because of the lossy compression method used, highly compressed digital video displays artifacts on playback. These artifacts appear as noise, blockiness or ringing on the edges of objects.
The tests in this chapter assess the video processor's ability to remove the compression artifacts while preserving the image detail.

2.3 Upscaled Compression Artifacts

Upscaled Compression Artifacts are most common when watching low resolution internet video on large screen, HD displays. As the images are upscaled, the artifacts also become larger and more obvious. As with the tests in the Compression Artifacts section, the tests in this chapter assess the video processor's ability to remove the artifacts while preserving the image detail. As the images have been upscaled, the noise reducer has to detect and process softer noise dispersed over a larger area.