Standard-definition television

SDTVstandard definitionSDstandard-definitionstandardSD Digitalstandard definition television(SDTV)625-line480i
Standard-definition television (SDTV or SD) is a television system which uses a resolution that is not considered to be either high or enhanced definition.wikipedia
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High-definition television

HDTVhigh definitionHD
Standard-definition television (SDTV or SD) is a television system which uses a resolution that is not considered to be either high or enhanced definition.
High-definition television (HDTV) is a television system providing an image resolution that is of substantially higher resolution than that of standard-definition television.

Enhanced-definition television

enhanced definitionEDTVED
Standard-definition television (SDTV or SD) is a television system which uses a resolution that is not considered to be either high or enhanced definition.
Specifically, this term defines formats that deliver a picture superior to that of standard-definition television (SDTV) but not as detailed as high-definition television (HDTV).

576i

625-line720x576analogue
The two common SDTV signal types are 576i, with 576 interlaced lines of resolution, derived from the European-developed PAL and SECAM systems; 480i based on the American NTSC system.
576i is a standard-definition video mode originally used for broadcast television in most countries of the world where the utility frequency for electric power distribution is 50 Hz. Because of its close association with the color encoding system, it is often referred to as simply PAL, PAL/SECAM or SECAM when compared to its 60 Hz (typically, see PAL-M) NTSC-color-encoded counterpart, 480i.

480i

480i60525 line525 lines
The two common SDTV signal types are 576i, with 576 interlaced lines of resolution, derived from the European-developed PAL and SECAM systems; 480i based on the American NTSC system.
480i is a shorthand name for the video mode used for standard-definition analog or digital television in Caribbean, Myanmar, Japan, South Korea, Taiwan, Philippines, Laos, Western Sahara, and most of the Americas (with the exception of Argentina, Paraguay and Uruguay).

NTSC

analog30panalogue broadcasting
The two common SDTV signal types are 576i, with 576 interlaced lines of resolution, derived from the European-developed PAL and SECAM systems; 480i based on the American NTSC system.
Digital broadcasting allows higher-resolution television, but digital standard definition television continues to use the frame rate and number of lines of resolution established by the analog NTSC standard.

Pan and scan

fullscreenpan-and-scanPan & Scan
In North America, digital SDTV is broadcast in the same 4:3 aspect ratio as NTSC signals, with widescreen content being center cut.
Pan and scan is a method of adjusting widescreen film images so that they can be shown in fullscreen proportions of a standard definition 4:3 aspect ratio television screen, often cropping off the sides of the original widescreen image to focus on the composition's most important aspects.

ATSC standards

ATSCdigitaldigital facilities
Standards that support digital SDTV broadcast include DVB, ATSC, and ISDB.
It also includes standard-definition formats, although initially only HDTV services were launched in the digital format.

Digital television

digitaldigital TVDTV
SDTV and high-definition television (HDTV) are the two categories of display formats for digital television (DTV) transmissions.
With digital terrestrial television (DTT) broadcasting, the range of formats can be broadly divided into two categories: high definition television (HDTV) for the transmission of high-definition video and standard-definition television (SDTV).

Pixel aspect ratio

square pixelsquare pixelsaspect ratio
For SMPTE 259M-C compliance, a SDTV broadcast image is scaled to 720 pixels wide for every 480 NTSC (or 576 PAL) lines of the image with the amount of non-proportional line scaling dependent on either the display or pixel aspect ratio.
However, some imaging systems, especially those that must be compatible with standard-definition television motion pictures, display an image as a grid of rectangular pixels, in which the pixel width and height are different.

Aspect ratio

4:3aspect ratiosaspect-ratio
In North America, digital SDTV is broadcast in the same 4:3 aspect ratio as NTSC signals, with widescreen content being center cut.
4:3 = 1.: Some (not all) 20th century computer monitors (VGA, XGA, etc.), standard-definition television

ISDB

ISDB-TISDB-SIntegrated Service Digital Broadcasting-Terrestrial
Standards that support digital SDTV broadcast include DVB, ATSC, and ISDB.
RCA video jack provides SDTV signal that is sampled down from the HDTV signal for analog CRT television sets or VCRs.

Interlaced video

interlacedinterlaceinterlacing
The two common SDTV signal types are 576i, with 576 interlaced lines of resolution, derived from the European-developed PAL and SECAM systems; 480i based on the American NTSC system.
480i: standard-definition interlaced video usually used in traditionally NTSC countries (North and parts of South America, Japan)

Multiplexing

multiplexedmultiplexmultiplexes
The last two were originally developed for HDTV, but are more often used for their ability to deliver multiple SD video and audio streams via multiplexing, than for using the entire bitstream for one HD channel.
This may involve several standard definition television (SDTV) programmes (particularly on DVB-T, DVB-S2, ISDB and ATSC-C), or one HDTV, possibly with a single SDTV companion channel over one 6 to 8 MHz-wide TV channel.

Nominal analogue blanking

In case of digital video line having 720 horizontal pixels, only the center 704 pixels contain actual 4:3 or 16:9 image, and the 8-pixel-wide stripes from either side are called nominal analogue blanking for horizontal blanking and should be discarded before displaying the image.
Nominal analog blanking or nominal analogue blanking is the outermost part of the overscan of a standard definition digital television image.

Overscan

underscancrop the edges of the pictureoverscan/underscan
Nominal analogue blanking should not be confused with overscan, as overscan areas are part of the actual 4:3 or 16:9 image.
Digital foundations to most storage and transmission systems since the early 1990s have meant that analogue NTSC has only been expected to have 480 lines of picture – see SDTV, EDTV, and DVD-Video.

PAL

colour television25p25
The two common SDTV signal types are 576i, with 576 interlaced lines of resolution, derived from the European-developed PAL and SECAM systems; 480i based on the American NTSC system.

SECAM

CIS-SECAMSECAM LSÉCAM
The two common SDTV signal types are 576i, with 576 interlaced lines of resolution, derived from the European-developed PAL and SECAM systems; 480i based on the American NTSC system.

16:9 aspect ratio

16:91.78:1widescreen
However, in other parts of the world that used the PAL or SECAM color systems, standard-definition television is now usually shown with a 16:9 aspect ratio, with the transition occurring between the mid-1990s and mid-2000s depending on region.

Digital Video Broadcasting

DVBDigital Video BroadcastDVB Project
Standards that support digital SDTV broadcast include DVB, ATSC, and ISDB.

Bitstream

bit streambyte streambinary sequence
The last two were originally developed for HDTV, but are more often used for their ability to deliver multiple SD video and audio streams via multiplexing, than for using the entire bitstream for one HD channel.

Television channel

channeltelevision channelsTV channel
The last two were originally developed for HDTV, but are more often used for their ability to deliver multiple SD video and audio streams via multiplexing, than for using the entire bitstream for one HD channel.

SMPTE 259M

SD-SDISMPTE 259
For SMPTE 259M-C compliance, a SDTV broadcast image is scaled to 720 pixels wide for every 480 NTSC (or 576 PAL) lines of the image with the amount of non-proportional line scaling dependent on either the display or pixel aspect ratio.

Letterboxing (filming)

letterboxletterboxedletterboxing
The display ratio for broadcast widescreen is commonly 16:9, the display ratio for a traditional or letterboxed broadcast is 4:3.

Refresh rate

refreshvertical frequencynew frame
SDTV refresh rates can be 24, 25, 30, 50 or 60 frames per second with a possible rate multiplier of 1000/1001 for NTSC.

Frame rate

frames per secondfpsframe/s
SDTV refresh rates can be 24, 25, 30, 50 or 60 frames per second with a possible rate multiplier of 1000/1001 for NTSC.