Standard-definition television (SDTV) is a somewhat out-of-date protocol for the broadcast and transmission of television. The key advantages of SDTV stem from the outdated nature of the technology. SDTV televisions are useful for backward compatibility with older videos and transmission networks. Older technologies tend to be less expensive, and this will remain true for older televisions until existing stocks of new and used standard sets have been sold off or wear out. This technology is being phased out worldwide, however, and the new high-definition television (HDTV) standard is technically superior in all regards.
The standard-definition television was ubiquitous for decades. A vast amount of information was recorded in this format, and backward-compatibility with this information is a key advantage of SDTV. Old home movies, off-the-air recordings, and other videos may not display properly on new HDTV sets, as these sets must adjust the image from its original format and aspect ratio.
Upgrading telecommunications networks to the new HDTV standard is expensive. Television stations in the United States took roughly a decade to make the upgrade, and many other nations have been unable or unwilling to make the transition. In these regions, SDTV remains in place because the economical use of existing hardware is more important than maximizing image quality.
The price of SDTV systems remains a key advantage. The electronics in standard-definition televisions are simpler to manufacture. Many consumers might opt to purchase sets in the older format and use adapter boxes to convert an HD signal to SD. This negates the benefits of the HDTV format but can be an economical option for anyone who is not especially interested in picture quality. Sets in the older format are typically quite inexpensive, especially when purchased used.
SDTV is a dying format, however, and broadcasters and consumers will eventually abandon it. The new HDTV format provides a clearer, sharper image with higher resolution. This improves the viewing experience, especially for viewers who own and watch large televisions. The standard definition format, after all, was designed for an era when televisions tended to be smaller, which meant that the overall resolution per inch of viewable area was quite good at the time.
An additional disadvantage of the SDTV format stems from the fact that it uses a great deal of bandwidth. As technology has improved, a greater and greater premium has been placed on space in the electromagnetic spectrum. HDTV signals, unlike their predecessors, are encoded digitally and require a smaller wavelength. The switch away from standard definition TV has freed up a large chunk of the EM spectrum which can be used for other transmissions.