Video interface

Digital video is an electronic representation of moving visual images (video) in the form of encoded digital data. This is in contrast to analog video, which represents moving visual images in the form of analog signals. Digital video comprises a series of digital images displayed in rapid succession.

Digital video is audio and video mixed together to make a production. the data gathered used to create a video, rather than a series of photos put together. Digital video have many advantages such as easy copying, multicasting, easy sharing and storage. Video recorded on tape is used on a computer on media player. Digital video is made of images displayed rapidly frequencies of 15, 24,30, and 60 frames per second.

Digital video was first introduced commercially in 1986 with the Sony D1 format, which recorded an uncompressed standard-definition component video signal in digital form. In addition to uncompressed formats, popular compressed digital video formats today include H.264 and MPEG-4. 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 generation loss. Digital video can be stored on digital media such as Blu-ray Disc, on computer data storage, or streamed over the Internet to end users who watch content on a desktop computer screen or a digital smart TV. Today, digital video content such as TV shows and movies also include a digital audio soundtrack.

History

Digital video cameras

The basis for digital video cameras are metal-oxide-semiconductor (MOS) image sensors. The first practical semiconductor image sensor was the charge-coupled device (CCD), invented in 1969 by Willard S. Boyle, who won a Nobel Prize for his work in physics. Following the commercialization of CCD sensors during the late 1970s to early 1980s, the entertainment industry slowly began transitioning to digital imaging and digital video over from analog video the next two decades. The CCD was followed by the CMOS active-pixel sensor (CMOS sensor), developed in the 1990s. CMOS are beneficial because of their small size, high speed, and low power usage. CMOS are most commonly found today in the digital cameras in iPhones, used as the image censor for the device.

Digital video coding

In the 1970s, pulse-code modulation (PCM) induced the birth of digital video coding, demanding high bitrates of 45-140 Mbps for standard-definition (SD) content. By the 1980s, the discrete cosine transform (DCT) became the standard for digital video compression.

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. 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, becoming first practical video coding standard. Since H.261, DCT compression has been adopted by all the major video coding standards that followed.

MPEG-1, developed by the Motion Picture Experts Group (MPEG), followed in 1991, and it was designed to compress VHS-quality video. It was succeeded in 1994 by MPEG-2/H.262, which became the standard video format for DVD and SD digital television. It was followed by MPEG-4/H.263 in 1999, and then in 2003 it was followed by H.264/MPEG-4 AVC, which has become the most widely used video coding standard.

Digital video production

Starting in the late 1970s to the early 1980s, video production equipment that was digital in its internal workings was introduced. These included time base correctors (TBC) and digital video effects (DVE) units. 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 Bosch (through their Fernseh division) and Ampex developed prototype digital videotape recorders (VTR) in their research and development labs. Bosch's machine used a modified 1 inch type B videotape transport and recorded an early form of CCIR 601 digital video. Ampex's prototype digital video recorder used a modified 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 by its developers as "Annie," 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 D1 format, which recorded an uncompressed standard definition component video signal in digital form. Component video connections required 3 cables, but most television facilities were wired for composite NTSC or PAL video using one cable. Due this incompatibility the cost of the recorder, D1 was used primarily by large television networks and other component-video capable video studios.

In 1988, Sony and Ampex co-developed and released the D2 digital videocassette format, which recorded video digitally without compression in ITU-601 format, much like D1. In comparison, D2 had the major difference of encoding the video in composite form to the NTSC standard, thereby only requiring single-cable composite video connections to and from a D2 VCR. This made it a perfect fit for the majority of television facilities at the time. D2 was a successful format in the television broadcast industry throughout the late '80s and the '90s. D2 was also widely used in that era as the master tape format for mastering laserdiscs.

D1 & D2 would eventually be replaced by cheaper systems using video compression, most notably Sony's Digital Betacam, that were introduced into the network's television studios. Other examples of digital video formats utilizing compression were Ampex's DCT (the first to employ such when introduced in 1992), the industry-standard DV and MiniDV and its professional variations, Sony's DVCAM and Panasonic's DVCPRO, and Betacam SX, a lower-cost variant of Digital Betacam using MPEG-2 compression.

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.

QuickTime, Apple Computer's multimedia framework, was released in June 1991. Audio Video Interleave from Microsoft followed in 1992. Initial consumer-level content creation tools were crude, requiring an analog video source to be digitized to a computer-readable format. While low-quality at first, consumer digital video increased rapidly in quality, first with the introduction of playback standards such as MPEG-1 and MPEG-2 (adopted for use in television transmission and DVD media), and the introduction of the DV tape format allowing recordings in the format to be transferred directly to digital video files using a FireWire port on an editing computer. This simplified the process, allowing non-linear editing systems (NLE) to be deployed cheaply and widely on