Standard-definition television

Standard-definition television SDTV, SD, often shortened to specifics definition is a television system which uses the resolution that is not considered to be either analog broadcast systems.

The two common SDTV signal classification are 576i, with 576 interlaced ordering of resolution, derived from the European-developed PAL as well as SECAM systems, as well as 480i based on the American NTSC system. Common SDTV refresh rates are 25, 29.97 as well as 30 frames per second. Both systems use a 4:3 aspect ratio.

Standards that support digital SDTV broadcast include , with the transition occurring between the mid-1990s and late-2000s depending on region. Older everyone with a 4:3 aspect ratio are broadcast with a flag that switches the display to 4:3.

Digital SDTV eliminates the ghosting and noisy images associated with analog systems. However, if the reception has interference or is poor, where the error correction cannot compensate one will encounter various other artifacts such(a) as abstraction freezing, stuttering or dropouts from missing intra-frames or blockiness from missing macroblocks.

Pixel aspect ratio

The table below summarizes pixel aspect ratios for the scaling of various kinds of SDTV video lines.

The pixel aspect ratio is the same for 720- and 704-pixel resolutions because the visible idea be it 4:3 or 16:9 is contained in the center 704 horizontal pixels of the digital frame. In the effect of a digital video set having 720 horizontal pixels including horizontal blanking, only the center 704 pixels contain the actual 4:3 or 16:9 image, and the 8-pixel-wide stripes on either side are called nominal analog blanking or horizontal blanking and should be discarded when displaying the image. Nominal analog blanking should not be confused with overscan, as overscan areas are part of the actual 4:3 or 16:9 image.

For SMPTE 259M-C compliance, an SDTV broadcast image is scaled to 720 pixels wide for every 480 NTSC or 576 PAL configuration of the image with the amount of non-proportional line scaling dependent on either the display or pixel aspect ratio. The display ratio for broadcast widescreen is commonly 16:9, the display ratio for a traditional or letterboxed broadcast is 4:3.

An SDTV image outside the constraints of the SMPTE indications requires no non-proportional scaling with 640 pixels for every line of the image. The display and pixel aspect ratio is loosely not so-called with the line height establishment the aspect. For widescreen 16:9, 360 lines define a widescreen image and for traditional 4:3, 480 lines define an image.