Low-definition television

Low-definition television or LDTV refers to television systems that have a lower screen resolution than standard-definition television systems. The term is usually used in reference to digital television, in particular when broadcasting at the same (or similar) resolution as analog TV systems.

Sources

The most common source of LDTV programming is the Internet, where mass distribution of higher-resolution video files could overwhelm computer servers and take too long to download. Most mobile phones and portable devices such as Apple’s video iPod, or Sony’s PlayStation Portable use LDTV video, as higher-resolution files would be excessive to the needs of their small screens (320×240 and 480×272 pixels respectively). The current generation of iPods still have LDTV screens, as does the iPhone (480×320).

An upcoming source of LDTV using standard broadcasting techniques are mobile TV services powered by DVB-H or DMB, or ATSC-M/H.

Older video game consoles such as the Nintendo Entertainment System generated a non-standard version of NTSC or PAL in which the two fields did not interlace, and instead were displayed directly on top of each other, keeping the orientation of the scanlines constant. This would be 240p and 288p respectively. The Video CD format was born on such a console (CD-i), and it likewise uses a progressive LDTV signal (352×240 or ×288), which is half the vertical resolution of SDTV.

A VHS videotape could be considered borderline SDTV (approximately 320×486), but any attempt to use VHS for professional production will yield results comparable to LDTV. VHS supports interlace and high motion, which are not typical of LDTV signals. Professional-level Betacam SP tape produces 440×486; some college TV studios use Super VHS at 560×486.

The NTSC PlayStation, for example, was capable of true 480i output, but most games used 240p mode due to limited graphics and CPU power.^[1]

More recent systems now always use properly interlaced NTSC or PAL, except when running games designed for older, but compatible systems. The PS2 generates 240p/288p if a PS1 game calls for this mode.

Teleconferencing LDTV

An upcoming source of LDTV using standard broadcasting techniques are mobile TV services powered by DVB-H, DMB, or ATSC-M/H – however this kind of LDTV transmission technology is based on existent LDTV teleconferencing standards that have been in place for a decade or more.

See also

Television portal

• Digital television
• Digital audio broadcasting
• DVB, ATSC, ISDB
• EDTV, HDTV
• MPEG

References

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v • d • e Digital Video Resolutions Designation Usage Examples Definition (lines) Rate (Hz) Interlaced (fields) Progressive (frames) Low; MP@LL LDTV, VCD 240; 288 (SIF)   24, 30; 25 Standard; MP@ML SDTV, SVCD, DVD, DV 480 (NTSC, PAL-M) 60 24, 30 576 (PAL, SECAM) 50 25 Enhanced EDTV 480; 576   60; 50 High; MP@HL HDTV, Blu-ray Disc, HDV 720   24, 30, 60; 25, 50 1080 50, 60 24, 30; 25 This table illustrates total horizontal and vertical pixel resolution via box size. It does not accurately reflect the screen or pixel shape (aspect ratio) of these formats, which is either 4:3, or 16:9.