Digital video

Source: Wikipedia, the free encyclopedia.
This article is about digital techniques applied to video. For the standard format for storing digital video, see DV (video format). For other uses, see Digital video (disambiguation).
Sony digital video camera used for recording content.

Digital video is an electronic representation of moving visual images (

frames per second
. Digital video has many advantages such as easy copying, multicasting, sharing and storage.

Digital video was first introduced commercially in 1986 with the

H.264 and AV1. Modern interconnect standards used for playback of digital video include HDMI, DisplayPort, Digital Visual Interface (DVI) and serial digital interface
(SDI).

Digital video can be copied and reproduced with no degradation in quality. In contrast, when analog sources are copied, they experience

movies also includes a digital audio
soundtrack.

History

Digital video cameras

Further information: Digital cinematography, Image sensor, and Video camera

The basis for

CMOS sensor),[5] developed in the 1990s.[6][7]

Major films

broadcast television.[12]

A Betacam SP camera, originally developed in 1986 by Sony.

Digital video coding

Further information: Video coding format § History

In the 1970s,

video compression.[13]

The first digital

video coding standard was H.120, created by the (International Telegraph and Telephone Consultative Committee) or CCITT (now ITU-T) in 1984. H.120 was not practical due to weak performance.[14] H.120 was based on differential pulse-code modulation (DPCM), a compression algorithm that was inefficient for video coding. During the late 1980s, a number of companies began experimenting with DCT, a much more efficient form of compression for video coding. The CCITT received 14 proposals for DCT-based video compression formats, in contrast to a single proposal based on vector quantization (VQ) compression. The H.261 standard was developed based on DCT compression,[15] becoming first practical video coding standard.[14] Since H.261, DCT compression has been adopted by all the major video coding standards that followed.[15]

H.264/MPEG-4 AVC, which has become the most widely used video coding standard.[16]

The current-generation video coding format is

AV1 format. As of 2019, AVC is by far the most commonly used format for the recording, compression and distribution of video content, used by 91% of video developers, followed by HEVC which is used by 43% of developers.[19]

Digital video production

Starting in the late 1970s to the early 1980s,

digital video effects (DVE) units.[c] They operated by taking a standard analog composite video
input and digitizing it internally. This made it easier to either correct or enhance the video signal, as in the case of a TBC, or to manipulate and add effects to the video, in the case of a DVE unit. The digitized and processed video information was then converted back to standard analog video for output.

Later on in the 1970s, manufacturers of professional video broadcast equipment, such as

2-inch quadruplex videotape
VTR (an Ampex AVR-3) fitted with custom digital video electronics and a special octaplex 8-head headwheel (regular analog 2" quad machines only used 4 heads). Like standard 2" quad, the audio on the Ampex prototype digital machine, nicknamed Annie by its developers, still recorded the audio in analog as linear tracks on the tape. None of these machines from these manufacturers were ever marketed commercially.

Digital video was first introduced commercially in 1986 with the Sony

television networks
and other component-video capable video studios.

A professional television studio set in Chile.

In 1988, Sony and Ampex co-developed and released the

laserdiscs.[d]

D1 & D2 would eventually be replaced by cheaper systems using video compression, most notably Sony's

Betacam SX, a lower-cost variant of Digital Betacam using MPEG-2 compression.[20]

The Sony logo, creator of the Betacam.

One of the first digital video products to run on personal computers was PACo: The PICS Animation Compiler from The Company of Science & Art in Providence, RI. It was developed starting in 1990 and first shipped in May 1991. PACo could stream unlimited-length video with synchronized sound from a single file (with the .CAV

file extension) on CD-ROM. Creation required a Mac, and playback was possible on Macs, PCs, and Sun SPARCstations.[21]

non-linear editing systems (NLE) to be deployed cheaply and widely on desktop computers
with no external playback or recording equipment needed.

The widespread adoption of digital video and accompanying compression formats has reduced the

tapeless camcorders based on flash memory
possible, among other innovations and efficiencies.

Digital video and culture

Culturally, digital video has allowed video and film to become widely available and popular, beneficial to entertainment, education, and research.[22] Digital video is increasingly common in schools, with students and teachers taking an interest in learning how to use it in relevant ways.[23] Digital video also has healthcare applications, allowing doctors to track infant heart rates and oxygen levels.[24]

In addition, the switch from analog to digital video impacted media in various ways, such as in how businesses use cameras for surveillance.

compressed in order to save storage space.[25]

Digital television

Digital television (DTV) is the production and transmission of digital video from networks to consumers. This technique uses digital encoding instead of analog signals used prior to the 1950s.[26] As compared to analog methods, DTV is faster and provides more capabilities and options for data to be transmitted and shared.[27]

Digital television's roots are tied to the availability of inexpensive, high-performance

Gbit/s for high-definition television (HDTV).[29][32]

Overview

Digital video comprises a series of

frames per second. Every frame is a digital image and so comprises a formation of pixels. The color of a pixel is represented by a fixed number of bits of that color where the information of the color is stored within the image.[33] For example, 8-bit captures 256 levels per channel, and 10-bit captures 1,024 levels per channel.[34] The more bits, the more subtle variations of colors can be reproduced. This is called the color depth
, or bit depth, of the video.

Interlacing

In interlaced video each frame is composed of two halves of an image. The first half contains only the odd-numbered lines of a full frame. The second half contains only the even-numbered lines. These halves are referred to individually as fields. Two consecutive fields compose a full frame. If an interlaced video has a frame rate of 30 frames per second the field rate is 60 fields per second, though both part of interlaced video, frames per second and fields per second are separate numbers.

A broadcast television camera at the Pavek Museum in Minnesota.

Bit rate and BPP

By definition, bit rate is a measurement of the rate of information content from the digital video stream. In the case of uncompressed video, bit rate corresponds directly to the quality of the video because bit rate is proportional to every property that affects the video quality. Bit rate is an important property when transmitting video because the transmission link must be capable of supporting that bit rate. Bit rate is also important when dealing with the storage of video because, as shown above, the video size is proportional to the bit rate and the duration. Video compression is used to greatly reduce the bit rate while having little effect on quality.[35]

Bits per pixel (BPP) is a measure of the efficiency of compression. A true-color video with no compression at all may have a BPP of 24 bits/pixel.

MPEG4
allows for fractional BPP values to exist.

Constant bit rate versus variable bit rate

BPP represents the average bits per pixel. There are compression algorithms that keep the BPP almost constant throughout the entire duration of the video. In this case, we also get video output with a constant bitrate (CBR). This CBR video is suitable for real-time, non-buffered, fixed bandwidth video streaming (e.g. in videoconferencing). Since not all frames can be compressed at the same level, because quality is more severely impacted for scenes of high complexity, some algorithms try to constantly adjust the BPP. They keep the BPP high while compressing complex scenes and low for less demanding scenes.[36] This way, it provides the best quality at the smallest average bit rate (and the smallest file size, accordingly). This method produces a variable bitrate because it tracks the variations of the BPP.

Technical overview

Standard film stocks typically record at 24 frames per second. For video, there are two frame rate standards: NTSC, at 30/1.001 (about 29.97) frames per second (about 59.94 fields per second), and PAL, 25 frames per second (50 fields per second). Digital video cameras come in two different image capture formats: interlaced and progressive scan. Interlaced cameras record the image in alternating sets of lines: the odd-numbered lines are scanned, and then the even-numbered lines are scanned, then the odd-numbered lines are scanned again, and so on.

One set of odd or even lines is referred to as a field, and a consecutive pairing of two fields of opposite parity is called a frame. Progressive scan cameras record all lines in each frame as a single unit. Thus, interlaced video captures the scene motion twice as often as progressive video does for the same frame rate. Progressive scan generally produces a slightly sharper image, however, motion may not be as smooth as interlaced video.

Digital video can be copied with no generation loss; which degrades quality in analog systems. However, a change in parameters like frame size, or a change of the digital format can decrease the quality of the video due to image scaling and transcoding losses. Digital video can be manipulated and edited on non-linear editing systems.

Digital video has a significantly lower cost than 35 mm film. In comparison to the high cost of film stock, the digital media used for digital video recording, such as flash memory or hard disk drive is very inexpensive. Digital video also allows footage to be viewed on location without the expensive and time-consuming chemical processing required by film. Network transfer of digital video makes physical deliveries of tapes and film reels unnecessary.

A short video sequence in native 16K.
A diagram of 35 mm film as used in Cinemscope cameras.

Digital television (including higher quality

streaming video and peer-to-peer
movie distribution.

Many types of video compression exist for serving digital video over the internet and on optical disks. The file sizes of digital video used for professional editing are generally not practical for these purposes, and the video requires further compression with codecs to be used for recreational purposes.

As of 2017[update], the highest

megapixels (15360 x 8640 pixels). The highest speed is attained in industrial and scientific high-speed cameras
that are capable of filming 1024x1024 video at up to 1 million frames per second for brief periods of recording.

Technical properties

Live digital video consumes bandwidth. Recorded digital video consumes data storage. The amount of bandwidth or storage required is determined by the frame size, color depth and frame rate. Each pixel consumes a number of bits determined by the color depth. The data required to represent a frame of data is determined by multiplying by the number of pixels in the image. The bandwidth is determined by multiplying the storage requirement for a frame by the frame rate. The overall storage requirements for a program can then be determined by multiplying bandwidth by the duration of the program.

These calculations are accurate for uncompressed video, but due to the relatively high bit rate of uncompressed video, video compression is extensively used. In the case of compressed video, each frame requires only a small percentage of the original bits. This reduces the data or bandwidth consumption by a factor of 5 to 12 times when using lossless compression, but more commonly, lossy compression is used due to its reduction of data consumption by factors of 20 to 200.[37][failed verification] Note that it is not necessary that all frames are equally compressed by the same percentage. Instead, consider the average factor of compression for all the frames taken together.

Interfaces and cables

Purpose-built digital video interfaces

General-purpose interfaces use to carry digital video

  • FireWire (IEEE 1394)
  • Universal Serial Bus
    (USB)

The following interface has been designed for carrying MPEG-Transport compressed video:

Compressed video is also carried using UDP-IP over Ethernet. Two approaches exist for this:

Other methods of carrying video over IP

Storage formats

Encoding

See also: Video coding format and Video codec
  • CCIR 601
    used for broadcast stations
  • VC-2
    also known as Dirac Pro
  • MPEG-4 good for online distribution of large videos and video recorded to flash memory
  • MPEG-2 used for DVDs, Super-VCDs, and many broadcast television formats
  • MPEG-1 used for video CDs
  • H.261
  • H.263
  • Blu-ray Discs
    and some broadcast television formats
  • H.265 also known as MPEG-H Part 2, or as HEVC
  • MOV used for QuickTime framework
  • Theora used for video on Wikipedia

Tapes

Main article: Videotape

Discs

The Blu-ray disc, a type of optical disc used for media storage.
See also: Optical disc
  • Blu-ray Disc
  • DVD
  • VCD

See also

Notes

  1. ^ Defined as the top 200 grossing live-action films
  2. ^ For example, the Thomson-CSF 9100 Digital Video Processor, an internally all-digital full-frame TBC introduced in 1980.
  3. Nippon Electric Corporation
    (NEC) E-Flex.
  4. 1" Type C videotape
  5. ^ In fact the still images correspond to frames only in the case of progressive scan video. In interlaced video, they correspond to fields. See § Interlacing for clarification.

References

  1. ISBN 9783319490885
    .
  2. ISBN 978-0-8194-3698-6
    .
  3. ISSN 1945-0699
    .
  4. ISBN 978-1-136-04042-9
    .
  5. ISBN 978-1-136-04042-9
    .
  6. doi:10.1109/JEDS.2014.2306412
    .
  7. S2CID 10556755
    .
  8. ^ "The use of digital vs celluloid film on Hollywood movies". Stephen Follows. 2019-02-11. Retrieved 2019-10-23.
  9. ^ "Robert Rodriguez Film Once Upon a Time in Mexico This is a structural review". WriteWork. Retrieved 2013-04-22.
  10. ^ "Maybe the war between digital and film isn't a war at all". The A.V. Club. 23 August 2018. Retrieved 26 November 2019.
  11. ^ Rizov, Vadim (24 April 2019). "24 Films Shot on 35mm Released in 2018". Filmmaker Magazine. Retrieved 2019-09-14.
  12. ^ "The Heart of a Phone Camera: The CMOS Active Pixel Image Sensor". large.stanford.edu. Retrieved 2021-03-26.
  13. OCLC 181368622
    .
  14. ^ a b c d "The History of Video File Formats Infographic". RealNetworks. 22 April 2012. Retrieved 5 August 2019.
  15. ^
    ISBN 9780852967102
    .
  16. OCLC 861797595.{{cite book}}: CS1 maint: location missing publisher (link
    )
  17. ^ Thomson, Gavin; Shah, Athar (2017). "Introducing HEIF and HEVC" (PDF). Apple Inc. Retrieved 5 August 2019.
  18. ^ "HEVC Patent List" (PDF). MPEG LA. Retrieved 6 July 2019.
  19. ^ "Video Developer Report 2019" (PDF). Bitmovin. 2019. Retrieved 5 November 2019.
  20. ISBN 978-0789702654
    .
  21. ^ "CoSA Lives: The Story of the Company Behind After Effects". Archived from the original on 2011-02-27. Retrieved 2009-11-16.
  22. S2CID 131426433
    .
  23. S2CID 145361658
    .
  24. S2CID 232070728
    .
  25. S2CID 212417006
    .
  26. OCLC 50684535
    .
  27. doi:10.1109/35.685371
    .
  28. Benton Foundation
    . 2008-12-23.
  29. ^ a b Barbero, M.; Hofmann, H.; Wells, N. D. (14 November 1991). "DCT source coding and current implementations for HDTV". EBU Technical Review (251). European Broadcasting Union: 22–33. Retrieved 4 November 2019.
  30. ^ "NextLevel signs cable deal - Dec. 17, 1997". money.cnn.com. Retrieved 9 August 2018.
  31. ^ "TCI faces big challenges - Aug. 15, 1996". money.cnn.com. Retrieved 9 August 2018.
  32. ^ Barbero, M.; Stroppiana, M. (October 1992). "Data compression for HDTV transmission and distribution". IEE Colloquium on Applications of Video Compression in Broadcasting: 10/1–10/5.
  33. ^ Winkelman, Roy (2018). "TechEase, What is bit depth?". Retrieved 2022-04-18.
  34. ^ Steiner, Shawn (12 December 2018). "B&H, 8-Bit, 10-Bit, What Does It All Mean for Your Videos?".
  35. OCLC 57585202
    .
  36. OCLC 1295602475.{{cite book}}: CS1 maint: location missing publisher (link
    )
  37. ^ Vatolin, Dmitriy. "Lossless Video Codecs Comparison 2007". www.compression.ru. Retrieved 2022-03-29.

External links

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