High-definition video

 ( Blu-ray Disc ) 

The current high-definition video standards in North America were developed during the course of the advanced television process initiated by the Federal Communications Commission in 1987 at the request of American broadcasters. In essence, the end of the 1980s was a death knell for most analog high definition technologies that had developed up to that time.

The FCC process, led by the Advanced Television Systems Committee (ATSC) adopted a ATSC standards from interlaced 1,080-line video (a technical descendant of the original analog NHK 1125/30 Hz system) with a maximum frame rate of 30 Hz, (60 fields per second) and 720-line video, progressively scanned, with a maximum frame rate of 60 Hz.

In the end, however, the DVB standard of resolutions (1080, 720, 480) and respective frame rates (24, 25, 30) were adopted in conjunction with the Europeans that were also involved in the same standardization process. The FCC officially adopted the ATSC transmission standard in 1996 (which included both HD and SD video standards).

In the early 2000s, it looked as if DVB would be the video standard far into the future. However, both Brazil and China have adopted alternative standards for high-definition video that preclude the interoperability that was hoped for after decades of largely non-interoperable analog TV broadcasting.

• The number of lines in the vertical display resolution. High-definition television (HDTV) resolution is 1,080 or 720 lines. In contrast, regular digital television (DTV) is 480 lines (upon which NTSC is based, 480 visible scanlines out of 525) or 576 lines (upon which PAL and SECAM are based, 576 visible scanlines out of 625). However, since HD is broadcast digitally, its introduction sometimes coincides with the introduction of DTV. Additionally, current DVD quality is not high-definition, although the high-definition disc systems Blu-ray Disc and the HD DVD are.
• The scanning system: (p) or interlaced scanning (i). Progressive scanning (p) redraws an image frame (all of its lines) when refreshing each image, for example 720p/1080p. Interlaced scanning (i) draws the image field every other line or odd-numbered lines during the first image refresh operation, and then draws the remaining even numbered lines during a second refreshing, for example 1080i. Interlaced scanning yields image resolution if subject is not moving, but loses up to half of the resolution and suffers combing artifacts when subject is moving.
• The number of frames or fields per second (Hz). In Europe more common (50 Hz) television broadcasting system and in USA (60 Hz). The 720p60 format is 1,280 × 720 , progressive encoding with 60 frames per second (60 Hz). The 1080i50/1080i60 format is 1920 × 1080 pixels, interlaced encoding with 50/60 fields, (50/60 Hz) per second. Two interlaced fields formulate a single frame, because the two fields of one frame are temporally shifted. Frame telecine and segmented frames are special techniques that allow transmitting full frames by means of interlaced video stream.

Often, the rate is inferred from the context, usually assumed to be either 50 Hz (Europe) or 60 Hz (USA), except for 1080p, which denotes 1080p24, 1080p25, and 1080p30, but also 1080p50 and 1080p60.

A Frame rate or field rate can also be specified without a resolution. For example, 24p means 24 progressive scan frames per second and 50i means 25 progressive frames per second, consisting of 50 interlaced fields per second. Most HDTV systems support some standard resolutions and frame or field rates. The most common are noted below. High-definition signals require a high-definition television or computer monitor in order to be viewed. High-definition video has an aspect ratio of 16:9 (1.78:1). The aspect ratio of regular widescreen film shot today is typically 1.85:1 or 2.39:1 (sometimes traditionally quoted at 2.35:1). Standard-definition television (SDTV) has a 4:3 (1.33:1) aspect ratio, although in recent years many broadcasters have transmitted programs squeezed horizontally in 16:9 anamorphic format, in hopes that the viewer has a 16:9 set which stretches the image out to normal-looking proportions, or a set which squishes the image vertically to present a letterbox view of the image, again with correct proportions.

The EU defines HD resolution as 1920 x 1080 pixels or 2 073 600 pixels and UHD resolution as 3840 x 2160 pixels or 8 294 400 pixels.

Also, there are less common but still popular UltraWide resolutions, such as p (1080p UltraWide).

There is also a WQHD+ option for some of these.

• Most computers are capable of HD or higher resolutions over VGA, DVI, HDMI and/or DisplayPort.
• The optical disc standard Blu-ray Disc can provide enough digital storage to store hours of HD video content. Digital Versatile Discs or DVDs (that hold 4.7 Gigabyte for a Single layer or 8.5 GB for a double layer), are not always up to the challenge of today's high-definition (HD) sets. Storing and playing HD movies requires a disc that holds more information, like a Blu-ray Disc (which hold 25 GB in single layer form and 50 GB for double layer) or the now-defunct High Definition Digital Versatile Discs (HD DVDs) which held 15 GB or 30 GB in, respectively, single and double layer variations.

Blu-ray Discs were jointly developed by 9 initial partners including Sony and Phillips (which jointly developed CDs for audio), and Pioneer (which developed its own Laser-disc previously with some success) among others. HD DVD discs were primarily developed by Toshiba and NEC with some backing from Microsoft, Warner Bros., Hewlett Packard, and others. On February 19, 2008, Toshiba announced it was abandoning the format and would discontinue development, marketing and manufacturing of HD DVD players and drives.

Depending upon available bandwidth and the amount of detail and movement in the image, the optimum format for video transfer is either 720p24 or 1080p24. When shown on television in PAL system countries, film must be projected at the rate of 25 frames per second by accelerating it by 4.1 percent. In NTSC standard countries, the projection rate is 30 frames per second, using a technique called 3:2 pull-down. One film frame is held for three video fields (1/20 of a second), and the next is held for two video fields (1/30 of a second) and then the process is repeated, thus achieving the correct film projection rate with two film frames shown in one twelfth of a second.

Older (pre-HDTV) recordings on video tape such as Betacam SP are often either in the form 480i60 or 576i50. These may be upconverted to a higher resolution format, but removing the interlace to match the common 720p format may distort the picture or require filtering which actually reduces the resolution of the final output.

Non-cinematic HDTV video recordings are recorded in either the 720p or the 1080i format. The format used is set by the broadcaster (if for television broadcast). In general, 720p is more accurate with fast action, because it progressively scans frames, instead of the 1080i, which uses interlaced fields and thus might degrade the resolution of fast images.

720p is used more for Internet distribution of high-definition video, because computer monitors progressively scan; 720p video has lower storage-decoding requirements than either the 1080i or the 1080p. This is also the medium for high-definition broadcasts around the world and 1080p is used for Blu-ray movies.

Depending on the year and format in which a movie was filmed, the exposed image can vary greatly in size. Sizes range from as big as 24 mm × 36 mm for VistaVision/Technirama 8 perforation cameras (same as 35 mm still photo film) going down through 18 mm × 24 mm for Silent Films or Full Frame 4 perforations cameras to as small as 9 mm × 21 mm in Academy Sound Aperture cameras modified for the Techniscope 2 perforation format. Movies are also produced using other , including 70 mm films (22 mm × 48 mm) or the rarely used 55 mm and Cinerama.

The four major film formats provide pixel resolutions (calculated from pixels per millimeter) roughly as follows:

• Academy Sound (Sound movies before 1955): 15 mm × 21 mm (1.375) = 2,160 × 2,970
• Academy camera US Widescreen: 11 mm × 21 mm (1.85) = 1,605 × 2,970
• Current Anamorphic Panavision ("Scope"): 17.5 mm × 21 mm (2.39) = 2,485 × 2,970
• Super-35 for Anamorphic prints: 10 mm × 24 mm (2.39) = 1,420 × 3,390

In the process of making prints for exhibition, this negative is copied onto other film (negative → interpositive → internegative → print) causing the resolution to be reduced with each emulsion copying step and when the image passes through a lens (for example, on a projector). In many cases, the resolution can be reduced down to 1/6 of the original negative's resolution (or worse). Note that resolution values for 70 mm film are higher than those listed above.

Although, HD cameras can be highly effective indoor, special industries with outdoor environments called for a need to produce much higher resolutions for effective coverage. The ever-evolving image sensor technologies allowed manufacturers to develop cameras with 10-20 MP resolutions, which therefore have become efficient instruments to monitor larger areas.

In order to further increase the resolution of security cameras, some manufacturers developed multi-sensor cameras. Within these devices several sensor-lens combinations produce the images, which are later merged during image processing. These security cameras are able to deliver even hundreds of megapixels with motion picture frame rate.

Such high resolutions, however, requires special recording, storage and also video stream display technologies.