High definition video (HDTV)
The term high definition video is inaccurate. When people talk about HD, they are generally referring to the widescreen format used in modern cinema. But when you try to figure out exactly how many pixels are in an image, what scanning method is used, and what the frame rate is, you won’t get a definitive answer. There are many different options.
For example, there are 18 different digital television (DTV) standards in the US Not all of these standards are high definition standards. In general, HD standards refer only to so-called “movie-like” standards with a wide 16: 9 aspect ratio. However, you can sometimes hear that 480p is also a high definition format.
How did you achieve all this? The development of the video industry began with the experiments of 1897 and gradually reached the experimental transmission of 1934, with an image format of 300 lines. The first NTSC standard (483 lines, black and white) appeared in 1941. In 1949, the NTSC standard for color images emerged. In 1967, Europe adopted the PAL (Phase Alternation by Line) and SECAM (Systeme Electronique Couleur Avec Memoire) standards.
The aspect ratio of the first NTSC standard was created based on 35mm film, or 4: 3. In the 1950s, the film industry began experimenting with wider formats (in other words, to keep up with color television). Widescreen cinema was meant to “immerse” the viewer in the image on the screen, filling the field of view as much as possible. For the most part, movies were still shown in 4: 3 format, but special masks or lenses were used on both cameras and projectors. Today the entire film industry works with a wide format. In 1968, television took its first steps to create its own widescreen image. The research department of Japan Broadcasting Corporation NHK has started to develop an HDTV system (HDTV, 1125 lines, 60 fields / sec). In 1981, Sony developed the first high definition video system (HDVS).
In 1995, the ATSC (a private organization Advanced Television Systems Committee – Committee for the development of advanced standards in the field of television) proposed a standard for the transmission of digital television signals. This standard was officially approved by the US Federal Communications Commission (FCC) in December 1996. Based on this standard, 18 different combinations of height, width, and frame rate are possible. Widescreen formats form the foundation of modern HD video formats.
Advanced TV Standards Committee (ATSC)
The private organization ATSC was founded in 1982 and had about 25 members. In 1984, their number increased to 50. The membership of the organization has grown rapidly from the moment it opened its doors to all participants in 1996, making it international. In 2001, ATSC had more than 200 members.
Please note that ATSC is a private international organization and should not be confused with the FCC’s Advanced TV Services Advisory Committee (FCC), created in 1987 to assist the FCC with technical issues and public relations.
The ATSC was created to develop arbitrary standards for all premium television systems, including high definition television. As mentioned above, in 1995 ATSC developed a standard for the transmission of digital TV signals and in December 1996 this standard was approved by the US FCC. According to this standard, the data transfer rate must be at 19.39 Mbit / s. The transmission speed of the digital TV signal is higher than the transmission speed of simple data due to digital error correction. ATSC signals (hereinafter referred to as ATSC signals) are still limited to the 6 MHz bandwidth, as in the NTSC standard.
ATSC signals can have different aspect ratios (4: 3 or 16: 9) and a different number of horizontal lines per frame. They can have different frame rates (24.30 or 60 frames per second). These can be odd fields (interlaced half frames) or gradually scanned frames. The sound is digital. The ATSC data transmission standards are based on the MPEG-2 standard. When broadcast on television, the data is compressed, “buffered” and decoded, and can then be viewed. This means that when you change channels, there is a slight delay during which the data goes to the buffer before the image appears.
