We propose a temporally adaptive 3-D subband coding (3-D SBC) technique to effectively exploit the temporal activities in the input image sequence. By using the rate-distortion (R-D) performance measure, we show the optimal number of temporal subbands can be easily determined. The base temporal subband, which yields much concentrated energy, is encoded using the H.261-like motion-compensated discrete cosine transform (MC-DCT) technique. While in the higher temporal subbands, the two-dimensional (2-D) adaptive wavelet packet bases are employed to exploit the various energy distributions, due to the moving components. In encoding the subbands, we employ adaptive scanning methods, followed by uniform step-size quantization with variablelength coding (VLC), and a coded/not-coded flag reduction technique based on the quadtree structure. From the simulation results, the proposed 3-D SBC provides about 0.29-to 3.14-dB PSNR gain over the H.261 technique and the temporally fixed 3-D SBC techniques at bit rates 300 to 512 Kbits/s.
In this paper, a new contour coding technique using motion information is proposed, for the objectoriented video coding. In the conventional technique using motion information by Gu [4], the regionbased motion compensation is performed, and only the contours neighbouring the motion-failure(MF) regions are encoded by the proper intra-frame contour coding technique. However, since even small local motions within a region may incur the MF regions, the temporal correlation of the contours cannot be effectively exploited by the conventional techniques. In our approach, those MF regions are significantly reduced by employing the two-stage motion compensation. While the region-based motion compensation is performed in the first stage, the MF regions proceed to the second stage motion compensation to find the contours in the previous frame which coincide with the contours of the MF regions. In addition, by introducing the notion of the error band, the current contours can be properly fitted to the motion compensated contours using inter-frame relationship of the contours. From the simulation result, it is shown that the proposed technique provides better performance than the conventional technique by Gu.Moreover, by varying the width N of the error band, it is shown that the bit amount for the shape information can be adjusted according to the channel condition.
In this paper, we propose a temporally adaptive three-dimensional subband coding (3D SBC) technique to effectively exploit the temporal activities in the input video. By using the rate-distortion performance measure, we show the optimal number of temporal subbands can be easily determined. The base temporal subband, which yields mich concentrated energy, is encoded using H.261-like motion compensated discrete cosine transform technique. While in the higher temporal subbands, the two-dimensional adaptive wavelet packet bases are employed to exploit the various energy distributions, due to the moving components. In encoding the subbands, we employ adaptive scanning methods, followed by uniform step-size quantization with variable length coding, and coded/not-coded flag reduction technique based the quadtree structure. From the simulation results, the proposed 3D SBC provides about 0.29 3.14 dB PSNR gain over the H.261 and the temporally fixed 3D SBC techniques.
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