Digital Signal Standards
Between 1941 and 1967, three major video standards were set. The U.S. NTSC standard was accepted by much of South and Central America and also Asian countries aligned politically with the United States. Germany initially developed the PAL system, but it is used throughout the world in English-speaking countries and those countries aligned politically with the United Kingdom and their former colonies. France followed with Sequential Color with Memory (SECAM), which was adopted by former French colonies and some Eastern bloc countries. The major problem with these three systems is not their difference in quality but that they are incompatible; a program originating in an NTSC camera or recorded on an NTSC recorder cannot be viewed on either a PAL or SECAM receiver or played back on either a PAL or SECAM recorder. NTSC varies from PAL and SECAM in line and frame rates.
As digital television is becoming the standard around the world, plans to create a universal standard have failed. Currently, three international transmission digital systems exist: Terrestrial Integrated Services Digital Broadcasting (ISDB-T), developed in Japan; Terrestrial Digital Video Broadcasting (DVB-T), developed in Europe; and Advanced Television Systems Committee Digital Television (ATSC-DTV), developed in the United States. In addition, the U.S. ATSC standard actually offers 18 different formats. The FCC refused to set specific technical standards, leaving the industry to decide among the available formats. Digital standards conversion equipment is available, but the equipment is expensive, and some loss in signal quality occurs during the conversion. With the continuing use of digital systems, the conversion between standards has become less of a problem.
The measurement of digital systems is based on the number of bits required to convert a signal from analog to digital. A bit is either an ON or an OFF signal, the basics of the binary digital system. The amount of memory (number of bits) required determines the quality of the conversion and the ability of a specific system to handle the number of bits. For example, 1 second of color video would require 28 megabytes of memory. To deal with that large amount of memory, most video signals are compressed. Compression is accomplished by using one of several Motion Pictures Expert Group (MPEG) systems that separate necessary information from redundant information to reduce the amount of memory required for any one segment or program.
INTERNATIONAL DTV STANDARDS
February 25th, 2010 (3 weeks ago) at 04:17
I like it
. I am grateful to you for that, but you deserve more thanks than that. I am color blind (protanopia to be precise). I use Safari browser (unsure if that is important), and many web sites are tricky to read due to an inconsiderate choice of colours employed ithe design. However, here, as the choice of colors is good, the website is quite tidy and simple to comprehend. I don’t know whether it was a intentional and kind undertaking, or simply good luck, but thanks anyway.