Block-based detection systems for visual artifact location
The core of many video coding standards is formed by the Discrete Cosine Transform (DCT) for de-correlating spatial video data. When quantizing DCT sub-bands, artifacts may appear such as mosquito noise and ringing. Spatial artifact reduction requires artifact location information, to control the filter process, thereby avoiding unnecessary blurring of artifact-free regions. This location information can be derived, either in the time- or frequency domain. As coding artifacts are most annoying in flat or low-frequency regions, the objective of the detector is to localize these artifact-sensitive locations. The detection accuracy, coverage and sensitivity differ between the two possible detection domains. The time-domain solution has a 10-97% location detection performance, whereas the frequency domain results in 70-100% detection performance.