Low-definition television

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Low-definition television (LDTV) refers to TV 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 low-definition analog television systems. Mobile DTV systems usually transmit in low definition, as do all slow-scan television systems.

Contents

Sources

The Video CD format uses a progressive scan LDTV signal[ citation needed ] (352×240 or 352×288), which is half the vertical and horizontal resolution of full-bandwidth SDTV. However, most players will internally upscale VCD material to 480/576 lines for playback, as this is both more widely compatible and gives a better overall appearance. No motion information is lost due to this process, as VCD video is not high-motion and only plays back at 25 or 30 frames per second, and the resultant display is comparable to consumer-grade VHS video playback.

For the first few years of its existence, YouTube offered only one, low-definition resolution of 256x144 or 144p at 30~50 fps or less, later extending first to widescreen 426×240, then to gradually higher resolutions; once the video service had become well established and had been acquired by Google, it had access to Google's radically improved storage space and transmission bandwidth, and could rely on a good proportion of its users having high-speed internet connections, [1] giving an overall effect reminiscent of early online video streaming attempts using RealVideo or similar services, where 160×120 at single-figure framerates was deemed acceptable to cater to those whose network connections could not sufficiently deliver 240p content.

Video games

Older video game consoles and home computers often generated a technically compliant analog 525-line NTSC or 625-line PAL signal, but only sent one field type rather than alternating between the two. This created a 262 or 312 line progressive scan signal (with half the vertical resolution), which in theory can be decoded on any receiver that can decode normal, interlaced signals. [2] [3] [4] [5]

Since the shadow mask and beam width of standard CRT televisions were designed for interlaced signals, these systems produced a distinctive fixed pattern of alternating bright and dark scan lines; many emulators for older systems offer video filters to recreate this effect. With the introduction of digital video formats these low-definition modes are usually referred to as 240p and 288p (with the standard definition modes being 480i and 576i).

With the introduction of 16-bit computers in the mid-1980s, such as the Atari ST and Amiga, followed by 16-bit consoles in the late 1980s and early 1990s, like the Sega Genesis and Super NES, [4] outputting the standard interlaced resolutions was supported for the first time, but rarely used due to heavy demands on processing power and memory. Standard resolutions also had a tendency to produce noticeable flicker at horizontal edges unless employed quite carefully, such as using anti-aliasing, which was either not available or computationally exorbitant. Thus, progressive output with half the vertical remained the primary format on most games of the fourth and fifth generation consoles (including the Sega Saturn, the Sony PlayStation and the Nintendo 64).

With the advent of sixth generation consoles and the launch of the Dreamcast, standard interlaced resolution became more common, and progressive lower resolution usage declined.

More recent game systems tend to use only properly interlaced NTSC or PAL in addition to higher resolution modes, except when running games designed for older, compatible systems in their native modes. The PlayStation 2 generates 240p/288p if a PlayStation game calls for this mode, as do many Virtual Console emulated games on the Nintendo Wii. Nintendo's official software development kit documentation for the Wii refers to 240p as 'non-interlaced mode' or 'double-strike'. [6] [7]

Shortly after the launch of the Wii Virtual Console service, many users with component video cables experienced problems displaying some Virtual Console games due to certain TV models/manufacturers not supporting 240p over a component video connection. Nintendo's solution was to implement a video mode which forces the emulator to output 480i instead of 240p, [8] however many games released prior were never updated. [9]

Teleconferencing LDTV

Sources of LDTV using standard broadcasting techniques include mobile TV services powered by DVB-H, 1seg, DMB, or ATSC-M/H. However, this kind of LDTV transmission technology is based on existent LDTV teleconferencing standards that have been in place since the late 1990s.[ citation needed ]

Resolutions

StandardClassResolutionPixelsAspect ratioNotes
MMS-Small96p128×9612,2884:3Lowest size recommended for use with 3GPP video transmitted by MMS to/from cellular phones, matching resolution of smallest generally used color cellphone screen.[ citation needed ]
QQVGA120p160×12019,2004:3Used with some webcams and early colour-screen cellular phones, commonly used in early desktop computer and online video applications. Lowest commonly used video resolution.
QCIF Webcam144p176×14425,344 SAR 11:9 / DAR 4:3Approximately one-sixth analogue PAL resolution (one-half horizontal, one-third vertical).[ citation needed ] Also the size recommended for "medium" quality MMS videos.[ citation needed ]
144p144p192×14427,6484:3The resolution 192×144 is used when 144p is selected on a fullscreen YouTube video.[ citation needed ]
YouTube 144p144p256×14436,86416:9One tenth of 1440p. The lowest resolution on YouTube since 2013. [10]
QnHD180p320×18057,60016:9
222p222p400×22288,80016:9Used in low-resolution Facebook widescreen videos.[ citation needed ]
QVGA, NTSC square pixel240p320×24076,8004:3Comparable to "low resolution" output of many popular home computers and games consoles, including VGA "Mode X". Used in some webcams and for video recordings in early/budget digital cameras and cameraphones, and low-end smartphone screens. Original YouTube resolution. Maximum recommended size for "large" MMS videos.
SIF (525) 240p352×24084,480SAR 22:15 / DAR 4:3NTSC-standard VCD / super-long-play DVD. Narrow/tall pixels.
NTSC widescreen240p426×240102,24016:9Same as current YouTube "240p" mode; screen resolution of some budget portable DVD players. Roughly one-third full NTSC resolution (half vertical, two thirds horizontal).[ citation needed ]
CIF / SIF (625)288p352×288101,376SAR 11:9 / DAR 4:3PAL-standard VCD / super-long-play DVD. Wide/short pixels. Also a common resolution in early webcam / video conferencing, and in advanced featurephones and smartphones of mid-2000s (ca 2006).[ citation needed ]
Widescreen CIF 288p512×288147,45616:9Widescreen version of 288p resolution
PSP 272p480×272130,56030:17Notionally 16:9 with slight left/right edge cropping. Used in many portable DVD player screens and other small-format devices besides.
360p360p480×360172,8004:3Uncommon, used in some lower-mid-market smartphone screens and as an intermediate screen resolution for some 1990s videogames.[ citation needed ]
QuickTime File Format 320p568×320181,76016:9Used for .MOV files recorded with iPhone cameras.[ citation needed ]
nHD 360p640×360230,40016:9Current base resolution in YouTube, labelled as "360p".[ citation needed ]
  • The lowest and least computationally demanding resolution supported by hardware able to run mainstream desktop operating systems;[ vague ] the lowest interruption-free resolution with low-end broadband connections.
  • Typically used as the base "SD" standard by VoD services due to subjective similarity (and similar pixel counts) to a mid-grade free-to-air broadcast picture.
  • Effectively, the resolution offered by any higher-definition 16:9 video scaled down for a standard 640×480 (VGA) computer screen. Offers 75% of the pixel count of a true anamorphic NTSC DVD image, or 89% of a letterboxed 16:9 image.
  • Historically used as an ad-hoc standard for intermediate-quality / CD-R-sized MPEG4 conversions on P2P file sharing networks.

See also

Related Research Articles

<span class="mw-page-title-main">Digital television</span> Television transmission using digital encoding

Digital television (DTV) is the transmission of television signals using digital encoding, in contrast to the earlier analog television technology which used analog signals. At the time of its development it was considered an innovative advancement and represented the first significant evolution in television technology since color television in the 1950s. Modern digital television is transmitted in high-definition television (HDTV) with greater resolution than analog TV. It typically uses a widescreen aspect ratio in contrast to the narrower format (4:3) of analog TV. It makes more economical use of scarce radio spectrum space; it can transmit up to seven channels in the same bandwidth as a single analog channel, and provides many new features that analog television cannot. A transition from analog to digital broadcasting began around 2000. Different digital television broadcasting standards have been adopted in different parts of the world; below are the more widely used standards:

<span class="mw-page-title-main">Standard-definition television</span> Digital TV with similar definition to analog broadcasts

Standard-definition television is a television system that uses a resolution that is not considered to be either high or enhanced definition. Standard refers to offering a similar resolution to the analog broadcast systems used when it was introduced.

<span class="mw-page-title-main">Interlaced video</span> Technique for doubling the perceived frame rate of a video display

Interlaced video is a technique for doubling the perceived frame rate of a video display without consuming extra bandwidth. The interlaced signal contains two fields of a video frame captured consecutively. This enhances motion perception to the viewer, and reduces flicker by taking advantage of the characteristics of the human visual system.

Progressive scanning is a format of displaying, storing, or transmitting moving images in which all the lines of each frame are drawn in sequence. This is in contrast to interlaced video used in traditional analog television systems where only the odd lines, then the even lines of each frame are drawn alternately, so that only half the number of actual image frames are used to produce video. The system was originally known as "sequential scanning" when it was used in the Baird 240 line television transmissions from Alexandra Palace, United Kingdom in 1936. It was also used in Baird's experimental transmissions using 30 lines in the 1920s. Progressive scanning became universally used in computer screens beginning in the early 21st century.

Enhanced-definition television, or extended-definition television (EDTV) is a Consumer Electronics Association (CEA) marketing shorthand term for certain digital television (DTV) formats and devices. Specifically, this term defines an extension of the standard-definition television (SDTV) format that enables a clearer picture during high-motion scenes compared to previous iterations of SDTV, but not producing images as detailed as high-definition television (HDTV).

<span class="mw-page-title-main">Anamorphic widescreen</span> Technique that compresses a widescreen image onto a 4:3 frame

Anamorphic widescreen is a process by which a widescreen image is horizontally compressed to fit into a storage medium with a narrower aspect ratio, reducing the horizontal resolution of the image while keeping its full original vertical resolution. Compatible play-back equipment can then expand the horizontal dimension to show the original widescreen image. This is typically used to allow one to store widescreen images on a medium that was originally intended for a narrower ratio, while using as much of the frame – and therefore recording as much detail – as possible.

<span class="mw-page-title-main">Display resolution</span> Width and height of a display in pixels

The display resolution or display modes of a digital television, computer monitor, or other display device is the number of distinct pixels in each dimension that can be displayed. It can be an ambiguous term especially as the displayed resolution is controlled by different factors in cathode-ray tube (CRT) displays, flat-panel displays and projection displays using fixed picture-element (pixel) arrays.

HD-MAC was a broadcast television standard proposed by the European Commission in 1986, as part of Eureka 95 project. It belongs to the MAC - Multiplexed Analogue Components standard family. It is an early attempt by the EEC to provide High-definition television (HDTV) in Europe. It is a complex mix of analogue signal, multiplexed with digital sound, and assistance data for decoding (DATV). The video signal was encoded with a modified D2-MAC encoder.

1080i is a term used in high-definition television (HDTV) and video display technology. It means a video mode with 1080 lines of vertical resolution. The "i" stands for interlaced scanning method. This format was once a standard in HDTV. It was particularly used for broadcast television. This is because it can deliver high-resolution images without needing excessive bandwidth. This format is used in the SMPTE 292M standard.

<span class="mw-page-title-main">480i</span> Standard-definition video mode

480i is the video mode used for standard-definition digital video in the Caribbean, Japan, South Korea, Taiwan, Philippines, Myanmar, Western Sahara, and most of the Americas. The other common standard definition digital standard, used in the rest of the world, is 576i.

<span class="mw-page-title-main">576i</span> Standard-definition video mode

576i is a standard-definition digital video mode, originally used for digitizing 625 line analogue 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 legacy colour encoding systems, it is often referred to as PAL, PAL/SECAM or SECAM when compared to its 60 Hz NTSC-colour-encoded counterpart, 480i.

576p is the shorthand name for a video display resolution. The p stands for progressive scan, i.e. non-interlaced, the 576 for a vertical resolution of 576 pixels. Usually it corresponds to a digital video mode with a 4:3 anamorphic resolution of 720x576 and a frame rate of 25 frames per second (576p25), and thus using the same bandwidth and carrying the same amount of pixel data as 576i, but other resolutions and frame rates are possible.

High-definition video is video of higher resolution and quality than standard-definition. While there is no standardized meaning for high-definition, generally any video image with considerably more than 480 vertical scan lines or 576 vertical lines (Europe) is considered high-definition. 480 scan lines is generally the minimum even though the majority of systems greatly exceed that. Images of standard resolution captured at rates faster than normal, by a high-speed camera may be considered high-definition in some contexts. Some television series shot on high-definition video are made to look as if they have been shot on film, a technique which is often known as filmizing.

<span class="mw-page-title-main">1080p</span> Video mode

1080p is a set of HDTV high-definition video modes characterized by 1,920 pixels displayed across the screen horizontally and 1,080 pixels down the screen vertically; the p stands for progressive scan, i.e. non-interlaced. The term usually assumes a widescreen aspect ratio of 16:9, implying a resolution of 2.1 megapixels. It is often marketed as Full HD or FHD, to contrast 1080p with 720p resolution screens. Although 1080p is sometimes referred to as 2K resolution, other sources differentiate between 1080p and (true) 2K resolution.

<span class="mw-page-title-main">Pixel aspect ratio</span> Proportion between the width and the height of a pixel

A Pixel aspect ratio is a mathematical ratio that describes how the width of a pixel in a digital image compared to the height of that pixel.

Analog high-definition television has referred to a variety of analog video broadcast television systems with various display resolutions throughout history.

Broadcast-safe video is a term used in the broadcast industry to define video and audio compliant with the technical or regulatory broadcast requirements of the target area or region the feed might be broadcasting to. In the United States, the Federal Communications Commission (FCC) is the regulatory authority; in most of Europe, standards are set by the European Broadcasting Union (EBU).

High-definition television (HDTV) describes a television or video system which provides a substantially higher image resolution than the previous generation of technologies. The term has been used since at least 1933; in more recent times, it refers to the generation following standard-definition television (SDTV). It is the standard video format used in most broadcasts: terrestrial broadcast television, cable television, satellite television.

GameCube accessories include first-party releases from Nintendo, and third-party devices, since the GameCube's launch in 2001.

Various accessories for the PlayStation 2 video game console have been produced by Sony, as well as third parties. These include controllers, audio and video input devices such as microphones and video cameras, and cables for better sound and picture quality.

References

  1. ↑ Robertson, Mark. "What Is This 144p Stuff, YouTube?". Tubular Insights. Tubular Insights & Tubular Labs, Inc. Retrieved 15 March 2021.[ dead link ]
  2. ↑ "Scanlines Demystified" . Retrieved 2010-06-03.
  3. ↑ "Connecting your old videogames to your new flatpanel TV set" . Retrieved 2010-06-03.
  4. 1 2 SNES Development Manual. Nintendo of America. 1993. p. 2-1-2. Retrieved 2017-08-28. The picture display on the Super Nintendo Entertainment System (Super NES) has two modes. One is an interlace mode, based on the television system. The other is a non-interlace mode, in which one frame takes 1/60th of a second. In the non-interlace mode the same position is scanned every field. Each frame consists of only 262 lines, half that of the interlace mode. There appears to be no flickering compared to the interlace mode, since each point on the screen is radiated every 1/60th of a second.
  5. ↑ Hinner, Martin. "PAL video timing specification". Martin Hinner's homepage. Retrieved 2022-10-20.
  6. ↑ "N64 Functions Reference Manual - Video Interface (VI) Management". Archived from the original on 2012-03-26. Retrieved 2011-06-27.
  7. ↑ "GameCube SDK - Video Interface Library (VI)" (PDF). p. 6. Archived from the original (PDF) on 2024-04-07. Retrieved 2011-06-27.
  8. ↑ "Nintendo Support - Display problems while playing Virtual Console games" . Retrieved 2011-06-27.
  9. ↑ "Wii Component cable Interlace Mode". Archived from the original on 2012-03-21. Retrieved 2011-06-27.
  10. ↑ A, Jean-Baptiste (2013-04-08). "YouTube propose la résolution 144p pour ses vidéos - KultureGeek". kulturegeek.fr (in French). Retrieved 2024-03-31.
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