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Trick mode or trick play is a feature of digital video systems, including digital video recorders and video on demand systems, that mimics the visual feedback given during fast-forward and rewind operations that were provided by analogue systems such as VCRs. Trick play manipulates the video stream to include only a subset of frames. [1]
With an analogue system, the visual fast-forward/rewind effect was generated simply by transmitting the frames faster and/or in reverse; there was an inevitable loss of frame synchronization or 'tearing' but this was accepted as the norm. With a digital system, the decoder may not be capable of processing the digital stream significantly faster than normal. Additionally, playback in reverse is not possible with certain types of temporal compression algorithms.
This is made harder by the fact that, in video compression systems such as MPEG-2 and H.264, many frames depend on previous frames for display, and hence cannot be decoded independently. Only certain "I" or "Intra" frames are independent. As a result, a system offering trick mode has to select only those frames for display, which requires analysis of the digital stream either at the time of playback or in advance.
In a single-user disk-based system, it is possible to scan the media file in real time to locate the independent frames, but in a network-based video-on-demand system, the bandwidth allocated to the client is fixed, so the server has to use pregenerated 'hint' or 'index' information to locate suitable frames, and then play them out at the selected fast-forward or rewind speed within the original bandwidth envelope. Alternatively, the server may pregenerate an entirely new video stream with at least one forward and backward speed and switch to it when requested.
A codec is a device or computer program that encodes or decodes a data stream or signal. Codec is a portmanteau of coder/decoder.
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, usually at 24, 30, or 60 frames per second. Digital video has many advantages such as easy copying, multicasting, sharing and storage.
MPEG-1 is a standard for lossy compression of video and audio. It is designed to compress VHS-quality raw digital video and CD audio down to about 1.5 Mbit/s without excessive quality loss, making video CDs, digital cable/satellite TV and digital audio broadcasting (DAB) practical.
Time-division multiplexing (TDM) is a method of transmitting and receiving independent signals over a common signal path by means of synchronized switches at each end of the transmission line so that each signal appears on the line only a fraction of time in an alternating pattern. It can be used when the bit rate of the transmission medium exceeds that of the signal to be transmitted. This form of signal multiplexing was developed in telecommunications for telegraphy systems in the late 19th century, but found its most common application in digital telephony in the second half of the 20th century.
Motion JPEG is a video compression format in which each video frame or interlaced field of a digital video sequence is compressed separately as a JPEG image.
WinDVD is a commercial DVD video player software for Microsoft Windows.
Betacam is a family of half-inch professional videocassette products developed by Sony in 1982. In colloquial use, Betacam singly is often used to refer to a Betacam camcorder, a Betacam tape, a Betacam video recorder or the format itself.
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.
Internet Protocol television (IPTV) is the delivery of television content over Internet Protocol (IP) networks. This is in contrast to delivery through traditional terrestrial, satellite, and cable television formats. Unlike downloaded media, IPTV offers the ability to stream the source media continuously. As a result, a client media player can begin playing the content almost immediately. This is known as streaming media.
576i is a standard-definition digital video mode, originally used for digitizing 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.
To fast-forward is to move forwards through a recording at a speed faster than that at which it would usually be played, for example two times or two point five times. The recordings are usually audio, video or computer data. It is colloquially known as 'f-forwarding'. On media control symbols, such as player buttons and interfaces, the function is commonly represented by two solid arrows pointing right and these typical icons were correctly recognised by 75% of a sample of European consumers. This symbol is represented in Unicode as U+23E9⏩BLACK RIGHT-POINTING DOUBLE TRIANGLE.
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.
Dolby Digital Plus, also known as Enhanced AC-3, is a digital audio compression scheme developed by Dolby Labs for the transport and storage of multi-channel digital audio. It is a successor to Dolby Digital (AC-3), and has a number of improvements over that codec, including support for a wider range of data rates, an increased channel count, and multi-program support, as well as additional tools (algorithms) for representing compressed data and counteracting artifacts. Whereas Dolby Digital (AC-3) supports up to five full-bandwidth audio channels at a maximum bitrate of 640 kbit/s, E-AC-3 supports up to 15 full-bandwidth audio channels at a maximum bitrate of 6.144 Mbit/s.
Flash Video is a container file format used to deliver digital video content over the Internet using Adobe Flash Player version 6 and newer. Flash Video content may also be embedded within SWF files. There are two different Flash Video file formats: FLV and F4V. The audio and video data within FLV files are encoded in the same way as SWF files. The F4V file format is based on the ISO base media file format, starting with Flash Player 9 update 3. Both formats are supported in Adobe Flash Player and developed by Adobe Systems. FLV was originally developed by Macromedia. In the early 2000s, Flash Video was the de facto standard for web-based streaming video. Users include Hulu, VEVO, Yahoo! Video, metacafe, Reuters.com, and many other news providers.
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 resolution as low-definition analog television systems. Mobile DTV systems usually transmit in low definition, as do all slow-scan television systems.
Α video codec is software or a device that provides encoding and decoding for digital video, and which may or may not include the use of video compression and/or decompression. Most codecs are typically implementations of video coding formats.
CDXL is motion video file format developed by Commodore in the late 1980s and early 1990s for the Amiga computer platform. It is notable for being one of the earliest formats created for motion video playback from CD-ROM.
ARINC 818: Avionics Digital Video Bus (ADVB) is a video interface and protocol standard developed for high bandwidth, low-latency, uncompressed digital video transmission in avionics systems. The standard, which was released in January 2007, has been advanced by ARINC and the aerospace community to meet the stringent needs of high performance digital video. The specification was updated and ARINC 818-2 was released in December 2013, adding a number of new features, including link rates up to 32X fibre channel rates, channel-bonding, switching, field sequential color, bi-directional control and data-only links.
Opus is a lossy audio coding format developed by the Xiph.Org Foundation and standardized by the Internet Engineering Task Force, designed to efficiently code speech and general audio in a single format, while remaining low-latency enough for real-time interactive communication and low-complexity enough for low-end embedded processors. Opus replaces both Vorbis and Speex for new applications, and several blind listening tests have ranked it higher-quality than any other standard audio format at any given bitrate until transparency is reached, including MP3, AAC, and HE-AAC.
A video coding format is a content representation format of digital video content, such as in a data file or bitstream. It typically uses a standardized video compression algorithm, most commonly based on discrete cosine transform (DCT) coding and motion compensation. A specific software, firmware, or hardware implementation capable of compression or decompression in a specific video coding format is called a video codec.
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