In free viewpoint video system, the color and the corresponding depth video are utilized to synthesize the virtual views
by depth image based rendering (DIBR) technique. Hence, high quality of depth videos is a prerequisite for high quality
of virtual views. However, depth variation, caused by scene variance and limited depth capturing technologies, may
increase the encoding bitrate of depth videos and decrease the quality of virtual views. To tackle these problems, a depth
preprocess method based on smoothing the texture and abrupt changes of depth videos is proposed to increase the
accuracy of depth videos in this paper. Firstly, a bilateral filter is adopted to smooth the whole depth videos and protect
the edge of depth videos at the same time. Secondly, abrupt variation is detected by a threshold calculated according to
the camera parameter of each video sequence. Holes of virtual views occur when the depth values of left view change
obviously from low to high in horizontal direction or the depth values of right view change obviously from high to low.
So for the left view, depth value difference in left side gradually becomes smaller where it is greater than the thresholds.
And then, in right side of right view is processed likewise. Experimental results show that the proposed method can
averagely reduce the encoding bitrate by 25% while the quality of the synthesized virtual views can be improve by
0.39dB on average compared with using original depth videos. The subjective quality improvement is also achieved.