Video Coding: An Introduction to Standard Codecs
From the ground up, this guide explains video coding algorithms to video compression systems, and more.
TABLE OF CONTENTS Video Coding: An Introduction to Standard Codecs
Chapter 2: Video Basics
Before discussing the fundamentals of video compression, let us look at how video signals are generated. Their characteristics will help us to understand how they can be exploited for bandwidth reduction without actually introducing perceptual distortions. In this regard, we will first look at image formation and colour video. Interlaced/progressive video is explained, and its impact on the signal bandwidth and display units is discussed. Representation of video in digital form and the need for bit rate reductions will be addressed. Finally, the image formats to be coded for various applications will be analysed.
2.1 Analogue Video
2.1.1 Scanning
Video signals are normally generated at the output of a camera by scanning a two-dimensional moving scene and converting them into a one-dimensional electric signal. A moving scene is a collection of individual pictures or images, where each scanned picture generates a frame of the picture. Scanning starts at the top-left corner of the picture and ends at the bottom-right.
The choice of number of scanned lines per picture is a trade-off between the bandwidth, flicker and resolution. Increasing the number of scanning lines per picture increases the spatial resolution. Similarly, increasing the number of pictures per second will increase the temporal resolution. There is a lower limit to the number of pictures per second, below which flicker becomes perceptible. Hence, flicker-free, high-resolution, video requires larger bandwidth.
If a frame is formed by the single scanning of a picture, it is called progressive scanning. Alternatively, two pictures may be...
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