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In television technology, Active Format Descriptor or Active Format Description (AFD) is a signal that broadcasters will transmit with the picture to enable 4:3 and 16:9 television sets to display picture in the intended aspect ratio. Essentially, AFD is a standard set of codes sent in the MPEG video stream that provides aspect ratio information to television or set-top-box decoders. AFD is used in the generation of Widescreen signaling. AFDs are not part of the core MPEG standard; they are a DVB extension, which has subsequently also been adopted by ATSC. 4:3 is a ratio. ...
The 16:9 aspect ratio (also known as widescreen) is an aspect ratio that is 16/9 or 1. ...
The aspect ratio of an image is its displayed width divided by its height (usually expressed as x:y). For instance, the aspect ratio of a traditional television screen is 4:3, or 1. ...
The Moving Picture Experts Group or MPEG is a working group of ISO/IEC charged with the development of video and audio encoding standards. ...
In television technology, widescreen signaling (WSS) is a digital stream embedded in the TV signal describing qualities of the broadcast, in particular the intended aspect ratio of the image. ...
Official DVB logo, found on compliant devices DVB, short for Digital Video Broadcasting, is a suite of internationally accepted, open standards for digital television maintained by the DVB Project, an industry consortium with more than 270 members, and published by a Joint Technical Committee (JTC) of European Telecommunications Standards Institute...
The Advanced Television Systems Committee (ATSC) is the group that helped to develop the new digital television standard for the United States, also adopted by Canada, Mexico, and South Korea and being considered by other countries. ...
Implementations
A 16:9 film may be broadcast with AFD 2, indicating that the whole frame is important. On a 4:3 TV, this will then be shown as a 16:9 letterbox to ensure no image is lost. 16:9 sports coverage on the other hand may be broadcast with AFD 7, indicating that it is safe to display only the central 4:3 region. On a 4:3 TV, the image will be cropped and it will be shown full-screen. The 16:9 aspect ratio (also known as widescreen) is an aspect ratio that is 16/9 or 1. ...
4:3 is a ratio. ...
Letterboxing is the practice of copying widescreen film to video formats while preserving the original aspect ratio. ...
As of 2006, AFDs are only broadcast in a minority of the countries using MPEG digital television. As a result, the quality of implementation in receivers is variable. Some receivers only respect the basic "active area" information. More fully-featured receivers also support the "safe area" information, and will use this to optimise the display for the shape of the viewer's screen. It has been suggested that Digital terrestrial television be merged into this article or section. ...
Many receivers currently have a bug in their handling of AFD 7, arising from an error in a table in the 2001 UK Digital Television Group receiver implementation guidelines. This causes 4:3-safe content like the sport mentioned above to be shown letterboxed on a 4:3 TV, instead of full-screen.
See also Letterboxing is the practice of copying widescreen film to video formats while preserving the original aspect ratio. ...
The inner box (green) is the format used in pre-1952 movies and pre-HDTV television. ...
In television technology, widescreen signaling (WSS) is a digital stream embedded in the TV signal describing qualities of the broadcast, in particular the intended aspect ratio of the image. ...
External links - ETSI TS 101 154 v1.7.1 - the latest version of the DVB standard that defines AFDs
- ATSC A/53 - the ATSC standard
- Digital TV Group AFD tutorial
- DTG digital receiver implementation guidelines
- Explanation of the error in the DTG guidelines
- Active Format Descriptors explanation
- AFD codes explained
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