High-definition video or HD video refers to any video system of higher resolution than standard-definition (SD) video, and most commonly involves display resolutions of 1,280x720 pixels (720p) or 1,920x1,080 pixels (1080i/1080p). This article discusses the general concepts of high-definition video, as opposed to its specific applications in television broadcast (HDTV), video recording formats (HDCAM, HDCAM-SR, DVCPRO HD, D5 HD, AVC-Intra, XDCAM HD, HDV, and AVCHD), the optical disc delivery system Blu-ray Disc, and the video tape format D-VHS.
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[citation needed] that preclude the interoperability that was hoped for after decades of largely non-interoperable analog TV broadcasting.
High definition video (prerecorded and broadcast) is defined by:
· 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/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 defunct HD DVD are.
· The scanning system: progressive scanning (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 greater 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 pixels, progressive encoding with 60 frames per second (60 Hz). The 1080i50 format is 1920 � 1080 pixels, interlaced encoding with 50 fields,(50 Hz) per second. Two interlaced fields formulate a single frame, because the two fields of one frame are temporally shifted. Frame pulldown 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.
|
Video mode |
Frame size px |
Pixels per image |
Scanning type |
Frame rate (Hz) |
720p |
1,280x720 |
921,600 |
Progressive |
23.976, 24, 25, 29.97, 30, 50, 59.94, 60, 72 |
1080i |
1,920x1,080 |
1.036,800 |
Interlaced |
25 (50 fields/s), 29.97 (59.94 fields/s), 30 (60 fields/s) |
1080p |
1,920x1,080 |
2,073,600 |
Progressive |
23.976, 24, 25, 29.97, 30, 50, 59.94, 60 |
|
Video mode |
Frame size px |
Pixels per image |
Scanning type |
Frame rate (Hz) |
2K |
2,048x1,536 |
3,145,728 |
Progressive |
|
2160p |
3,840x2,160 |
8,294,400 |
Progressive |
|
4K |
4,096x3,072 |
12,582,912 |
Progressive |
|
2540p |
4,520x2,540 |
11,480,800 |
Progressive |
|
4320p |
7,680x4,320 |
33,177,600 |
Progressive |
50, 60 |
High-definition image sources include terrestrial broadcast, direct broadcast satellite, digital cable, high definition disc (BD), internet downloads and the latest generation of video game consoles.
· Most computers are capable of HD or higher resolutions over VGA, DVI, and/or HDMI.
· The optical disc standard Blu-ray Disc can provide enough digital storage to store hours of HD video content. DVDs look best on screens that are smaller than 36 inches (91 cm), so they 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.
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