Deghosting based on in-loop selective filtering using motion vector information for low-bit-rate-video coding

In this paper, a technique is presented to alleviate ghosting artifacts in the decoded video sequences for low-bit-rate video coding. Ghosting artifacts can be defined as the appearance of ghost like outlines of an object in a decoded video frame. Ghosting artifacts result from the use of a prediction loop in the video codec, which is typically used to increase the coding efficiency of the video sequence. They appear in the presence of significant frame-to-frame motion in the video sequence, and are typically visible for several frames until they eventually die out or an intra-frame refresh occurs. Ghosting artifacts are particularly annoying at low bit rates since the extreme loss of information tends to accentuate their appearance. To mitigate this effect, a procedure with selective in-loop filtering based on motion vector information is proposed. In the proposed scheme, the in-loop filter is applied only to the regions where there is motion. This is done so as not to affect the regions that are devoid of motion, since ghosting artifacts only occur in high-motion regions. It is shown that the proposed selective filtering method dramatically reduces ghosting artifacts in a wide variety of video sequences with pronounced frame-to-frame motion, without degrading the motionless regions.