Playing back the series of frames produces the appearance of motion. 2.3.2 Temporal SamplingĪ moving video image is captured by taking a rectangular ‘snapshot’ of the signal at periodic time intervals. Choosing a ‘coarse’ sampling grid (the black grid in Figure 2.3) produces a low-resolution sampled image (Figure 2.4) whilst increasing the number of sampling points slightly (the grey grid in Figure 2.3) increases the resolution of the sampled image (Figure 2.5). The visual quality of the image is inﬂuenced by the number of sampling points. Sampling occurs at each of the intersection points on the grid and the sampled image may be reconstructed by representing each sample as a square picture element (pixel). Figure 2.3 shows a continuous-tone frame with two different sampling grids superimposed upon it. The most common format for a sampled image is a rectangle with the sampling points positioned on a square or rectangular grid. Sampling the signal at a point in time produces a sampled image or frame that has deﬁned values at a set of sampling points.

The output of a CCD array is an analogue video signal, a varying electrical signal that represents a video image. In the case of colour image capture, each colour component is separately ﬁltered and projected onto a CCD array (see Section 2.4). To obtain a 2D sampled image, a camera focuses a 2D projection of the video scene onto a sensor, such as an array of Charge Coupled Devices (CCD array).

6.4.11 The Complete Transform, Quantisation, Rescaling and Inverse Transform Process.

4.2.5 Deciding the Content of the Standards.

3.3.4 Motion Compensated Prediction of a Macroblock.

3.3.1 Prediction from the Previous Video Frame.

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