Image Processing Reference
In-Depth Information
relevant to understanding how TV works and by implication how compression has to
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
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.
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
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
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
This is a transmission modulation technique used in some parts of
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