Video - A Practical Guide to Video and Audio Compression - page 78

relevant to understanding how TV works and by implication how compression has to
work:

Picture sizes on different TV systems

●

Frame rates in the United States, Europe, and elsewhere

●

Aspect ratios and conversion between them

●

Analog waveforms and how to code a digital image from them

●

Coding of luma and chroma

●

5.3 Television Standards

There are a variety of standards that describe how TV is delivered. These have evolved
over the years. New work is underway to accommodate high-definition formats and dig-
ital television delivery. The convergence between TV systems and computer imaging tech-
nology is also significantly affecting this. There are two principal standards for analog TV:
NTSC and PAL. Some derivative standards are based on variants of these. In France, the
SECAM system is used, but this is broadly similar to PAL.

5.4 Frame Rates

One of the things that you will encounter when compressing video is the capability to
change the frame rate of the compressed output. You must be aware of the various source
frame rates. If you are creating video to be played back on a variety of platforms, and they
include TV systems, then choosing the wrong frame rate will detrimentally affect the qual-
ity of the playback experience.

Table 5-1 Analog TV Standards

Standard Description

NTSC NTSC is the way that analog TV is broadcast in the United States,

although this does not actually describe a picture size, resolution, or frame
rate.

PAL The broadcasting TV standard in the UK is PAL. It is a coding and

modulation scheme for transmitting video in the most economic
bandwidth over analog broadcast systems. Therefore, it is an analog
compression scheme and does not describe a physical presentation
format.

SECAM This is a transmission modulation technique used in some parts of

Europe.