Reduction of Dot Crawl and Rainbow Artifacts in the NTSC Video

Abstract

In the encoder of the National Television System Committee (NTSC) system, a composite video burst signal (CVBS) is generated using the luminance (Y) signal and the quadrature amplitude modulation (QAM) modulated chrominance (C) signal. In the decoder, it is important that the CVBS be accurately separated into luminance and chrominance signals by a Y/C separation filter. Otherwise, various artifacts, such as dot crawl, rainbow effect, and color bleeding, appear in a decoded video, degrading the quality of the decoded video. In addition, modern high-definition television (HDTV) system suffers from outdated analog decoding artifacts when HDTV compression techniques were applied to the not ideally decoded former standard-definition format video images. This paper proposes artifact reduction methods of dot crawl and rainbow effect using the characteristics of the CVBS video. The proposed artifact reduction algorithms use two successive frames, in which the decoded video images are divided into not moving (stationary) and moving regions. The stationary regions are filtered by a temporal filter, whereas the moving regions are further classified into three subdivided regions of different types of artifacts to apply them into temporal or spatial filters because inappropriately temporally filtered moving region delivers jitters on the edge. In the proposed algorithms, considering characteristics of the NTSC decoded image, a block matching algorithm based on 4x4 non-overlapping blocks is used for motion estimation and compensation. Computer simulations with various simulated and real videos containing NTSC artifacts show the effectiveness of the proposed artifact reduction methods.