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Theora
Theora is a free lossy video compression format. It was developed by the Xiph.Org Foundation and distributed without licensing fees alongside their other free and open media projects, including the Vorbis audio format and the Ogg container. The libtheora video codec is the reference implementation of the Theora video compression format developed by the Xiph.Org Foundation. Theora was derived from the formerly proprietary VP3 codec, released into the public domain by On2 Technologies. It is broadly comparable in design and bitrate efficiency to MPEG-4 Part 2, early versions of Windows Media Video, and RealVideo while it lacked some of the features present in some of these other codecs. It is comparable in open standards philosophy to the BBC's Dirac codec. Theora was named after Theora Jones, Edison Carter's Controller on the '' Max Headroom'' television program. Technical details Theora is a variable-bitrate, DCT-based video compression scheme. Like most ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dirac (video Compression Format)
Dirac (and Dirac Pro, a subset standardised as SMPTE VC-2) is an open and royalty-free video compression format, specification and software video codec developed by BBC Research & Development. Dirac aimed to provide high-quality video compression for Ultra HDTV and competed with existing formats such as H.264. The specification was finalised in January 2008, and further developments were only bug fixes and constraints. In September of that year, version 1.0.0 of an I-frame only subset known as Dirac Pro was released and was standardised by the SMPTE as VC-2. Version 2.2.3 of the full Dirac specification, including motion compensation and inter-frame coding, was issued a few days later. Dirac Pro was used internally by the BBC to transmit HDTV pictures at the Beijing Olympics in 2008. Two open source and royalty-free video codec software implementations, libschrodinger and dirac-research, were developed. The format implementations were named in honour of the theoretical ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vorbis
Vorbis is a free and open-source software project headed by the Xiph.Org Foundation. The project produces an audio coding format and software reference encoder/decoder ( codec) for lossy audio compression, libvorbis. Vorbis is most commonly used in conjunction with the Ogg container format and it is therefore often referred to as Ogg Vorbis. Version 1.0 of Vorbis was released in May 2000. Since 2013, the Xiph.Org Foundation has stated that the use of Vorbis should be deprecated in favor of the Opus codec, an improved and more efficient format that has also been developed by Xiph.Org. Name Vorbis is named after the character Exquisitor Vorbis in the '' Discworld'' novel '' Small Gods'' by Terry Pratchett. The Ogg format is named after ''ogging'', jargon from the computer game '' Netrek''. Development Vorbis is a continuation of audio compression development started in 1993 by Chris Montgomery. Intensive development began following a September 1998 letter from the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Xiph
The Xiph.Org Foundation is a nonprofit organization that produces free software, free multimedia formats and software tools. It focuses on the Ogg family of formats, the most successful of which has been Vorbis, an open and freely licensed audio format and codec designed to compete with the patented Windows Media Audio, WMA, MP3 and Advanced audio coding, AAC. As of 2013, development work was focused on Daala, an open and patent-free video format and codec designed to compete with VP9 and the patented High Efficiency Video Coding. In addition to its in-house development work, the foundation has also brought several already-existing but complementary free software projects under its aegis, most of which have a separate, active group of developers. These include Speex, an audio codec designed for speech, and Free Lossless Audio Codec, FLAC, a lossless audio codec. The Xiph.Org Foundation has criticized Microsoft and the Recording Industry Association of America, RIAA for their ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Proprietary Software
Proprietary software is computer software, software that grants its creator, publisher, or other rightsholder or rightsholder partner a legal monopoly by modern copyright and intellectual property law to exclude the recipient from freely sharing the software or modifying it, and—in some cases, as is the case with some patent-encumbered and EULA-bound software—from making use of the software on their own, thereby restricting their freedoms. Proprietary software is a subset of non-free software, a term defined in contrast to free and open-source software; non-commercial licenses such as CC BY-NC are not deemed proprietary, but are non-free. Proprietary software may either be closed-source software or source-available software. Types Origin Until the late 1960s, computers—especially large and expensive mainframe computers, machines in specially air-conditioned computer rooms—were usually leased to customers rather than Sales, sold. Service and all software available ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Block (data Storage)
In computing (specifically data transmission and data storage), a block, sometimes called a physical record, is a sequence of bytes or bits, usually containing some whole number of records, having a fixed length; a ''block size''. Data thus structured are said to be ''blocked''. The process of putting data into blocks is called ''blocking'', while ''deblocking'' is the process of extracting data from blocks. Blocked data is normally stored in a data buffer, and read or written a whole block at a time. Blocking reduces the overhead and speeds up the handling of the data stream. For some devices, such as magnetic tape and CKD disk devices, blocking reduces the amount of external storage required for the data. Blocking is almost universally employed when storing data to 9-track magnetic tape, NAND flash memory, and rotating media such as floppy disks, hard disks, and optical discs. Most file systems are based on a block device, which is a level of abstraction for the hard ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chroma Subsampling
Chroma subsampling is the practice of encoding images by implementing less resolution for Chrominance, chroma information than for luma (video), luma information, taking advantage of the human visual system's lower acuity for color differences than for luminance. It is used in many video and still image encoding schemesboth analog and digitalincluding in JPEG encoding. Rationale Digital signals are often compressed to reduce file size and save transmission time. Since the human visual system is much more sensitive to variations in brightness than color, a video system can be optimized by devoting more bandwidth to the luma (video), luma component (usually denoted Y'), than to the color difference components Cb and Cr. In compressed images, for example, the 4:2:2 Y'CbCr scheme requires two-thirds the bandwidth of non-subsampled "4:4:4" R'G'B'. This reduction results in almost no visual difference as perceived by the viewer. How subsampling works The Visual perception, human vi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Discrete Cosine Transform
A discrete cosine transform (DCT) expresses a finite sequence of data points in terms of a sum of cosine functions oscillating at different frequency, frequencies. The DCT, first proposed by Nasir Ahmed (engineer), Nasir Ahmed in 1972, is a widely used transformation technique in signal processing and data compression. It is used in most digital media, including digital images (such as JPEG and HEIF), digital video (such as MPEG and ), digital audio (such as Dolby Digital, MP3 and Advanced Audio Coding, AAC), digital television (such as SDTV, HDTV and Video on demand, VOD), digital radio (such as AAC+ and DAB+), and speech coding (such as AAC-LD, Siren (codec), Siren and Opus (audio format), Opus). DCTs are also important to numerous other applications in science and engineering, such as digital signal processing, telecommunication devices, reducing network bandwidth usage, and spectral methods for the numerical solution of partial differential equations. A DCT is a List of Fourier ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Variable Bitrate
Variable bitrate (VBR) is a term used in telecommunications and computing that relates to the bitrate used in sound or video encoding. As opposed to constant bitrate (CBR), VBR files vary the amount of output data per time segment. VBR allows a higher bitrate (and therefore more storage space) to be allocated to the more complex segments of media files while less space is allocated to less complex segments. The average of these rates can be calculated to produce an average bitrate for the file. MP3, WMA and AAC audio files can optionally be encoded in VBR, while Opus and Vorbis are encoded in VBR by default. Variable bit rate encoding is also commonly used on MPEG-2 video, MPEG-4 Part 2 video ( Xvid, DivX, etc.), MPEG-4 Part 10/H.264 video, Theora, Dirac and other video compression formats. Additionally, variable rate encoding is inherent in lossless compression schemes such as FLAC and Apple Lossless. Advantages and disadvantages of VBR The advantages of VBR are that ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Max Headroom (TV Series)
''Max Headroom'' is an American satirical cyberpunk science fiction television series by Chrysalis Visual Programming and Lakeside Productions for Lorimar-Telepictures that aired in the United States on ABC from March 31, 1987, to May 5, 1988. The series is set in a futuristic dystopia ruled by an oligarchy of television networks, and features the character and media personality Max Headroom. The story is based on the Channel 4 British TV film produced by Chrysalis, '' Max Headroom: 20 Minutes into the Future''. Premise In the future, an oligarchy of television networks rules the world. Even the government functions primarily as a puppet of the network executives, serving mainly to pass laws—such as banning "off" switches on televisions—that protect and consolidate the networks' power. Television technology has advanced to the point that viewers' physical movements and thoughts can be monitored through their television sets. Almost all non-television technology has b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
RealVideo
RealVideo, also spelled as Real Video, is a suite of proprietary format, proprietary video compression formats developed by RealNetworks — the specific format changes with the version. It was first released in 1997 and was at version 15. RealVideo is supported on many platforms, including Microsoft Windows, Windows, MacOS, Mac, Linux, Solaris, and several mobile phones. RealVideo is usually paired with RealAudio and packaged in a RealMedia (.rm) container. RealMedia is suitable for use as a streaming media format, that one is viewed while it is being sent over the network. Streaming video can be used to watch live television since it does not require downloading the entire video in advance. Technology The first version of RealVideo was announced in 1997 and was based on the H.263 format. At the time, RealNetworks issued a press release saying they had licensed Iterated Systems' ClearVideo technology and were including it as the RealVideo Fractal Codec. However, support for Cle ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
