From Video Coding: An Introduction to Standard Codecs

9.1 Video Object Plane (VOP)

In object-based coding the video frames are defined in terms of layers of video object planes (VOP). Each video object plane is then a video frame of a specific object of interest to be coded, or to be interacted with. Figure 9.1(a) shows a video frame that is made of three VOPs. In this figure, the two objects of interest are the balloon and the aeroplane. They are represented with their video object planes of VOP 1 and VOP 2. The remaining part of the video frame is regarded as a background, represented with VOP 0. For coding applications, the background is coded only once, and the other object planes are encoded through the time. At the receiver the reconstructed background is repeatedly added to the other decoded object planes. Since in each frame the encoder only codes the objects of interest (e.g. VOP 1 and/or VOP 2), and usually these objects represent a small portion of the video frame, then the bit rate of the encoded video stream can be extremely low. Note that, had the video frame of Figure 9.1(a) been coded with a conventional codec such as H.263, since clouds in the background move, then the H.263 encoder will inevitably encode most parts of the picture, with a much higher bit rate than that generated from the two objects.

Figure 9.1: (a) A Video Frame Composed of (b) Balloon VOP 1, (c) Aeroplane VOP 2

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Topics of Interest

9.2 Image Segmentation If VOPs are not available, then video frames need to be segmented into objects and a VOP to be derived for each one. In general, segmentation consists of extracting image...

9.5 Texture Coding The intra VOPs and motion compensated inter VOPs are coded with 8 8 block DCT. The DCT is performed separately for each of the luminance and chrominance planes. For an arbitrarily...

O. URHAN, S. ERT RK Electronics and Telecommunications Engineering Department, Veziroglu Campus, University of Kocaeli, 41040, Kocaeli, TR. & LATARUB Research Centre, University of Kocaeli, Kocaeli,...

9.4 Motion Estimation and Compensation The texture of each VOP is motion compensated prior to coding. The motion estimation and compensation is similar to that of H.263 with the exception that the...

9.3 Shape Coding The binary and grey scale shapes are normally referred to binary and grey scale alpha planes. Binary alpha planes are encoded with one of the binary shape coding methods (to be...