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Minnesota Twins | 2019 | On May 8, in an effort to get fans back to the ballpark, the Twins announced a flash sale of $5 tickets for their remaining home games in May. The Twins sold 20,000 tickets within a day, and had to make additional seating available due to the overwhelming demand. | wiki:25700001 |
Minnesota Twins | Threatened contraction or relocation of the team | The quirks of the Hubert H. Humphrey Metrodome, including the turf floor and the white roof, gave the Twins a significant home-field advantage that played into their winning the World Series in both 1987 and 1991, at least in the opinion of their opponents, as the Twins went 12–1 in postseason home games during those two seasons. These were the first two World Series in professional baseball history in which a team won the championship by winning all four home games. (The feat has since been repeated once, by the Arizona Diamondbacks in 2001.) Nevertheless, the Twins argued that the Metrodome was obsolete and that the lack of a dedicated baseball-only ballpark limited team revenue and made it difficult to sustain a top-notch, competitive team (the Twins had been sharing tenancy in stadiums with the NFL's Minnesota Vikings since 1961). | wiki:25700002 |
Minnesota Twins | Threatened contraction or relocation of the team | The team was rumored to contemplate moving to such places as New Jersey, Las Vegas, Portland, Oregon, the Greensboro/Winston-Salem, North Carolina area, and elsewhere in search of a more financially competitive market. In 2002, the team was nearly disbanded when Major League Baseball selected the Twins and the Montreal Expos (now the Washington Nationals franchise) for elimination due to their financial weakness relative to other franchises in the league. The impetus for league contraction diminished after a court decision forced the Twins to play out their lease on the Metrodome. However, Twins owner Carl Pohlad continued his efforts to relocate, pursuing litigation against the Metropolitan Stadium Commission and obtaining a state court ruling that his team was not obligated to play in the Metrodome after the 2006 season. | wiki:25700003 |
Minnesota Twins | Threatened contraction or relocation of the team | This cleared the way for the Twins to either be relocated or disbanded prior to the 2007 season if a new deal was not reached. | wiki:25700004 |
Minnesota Twins | Target Field | In response to the threatened loss of the Twins, the Minnesota private and public sector negotiated and approved a financing package for a replacement stadium— a baseball-only outdoor, natural turf ballpark in the Warehouse District of downtown Minneapolis— owned by a new entity known as the Minnesota Ballpark Authority. Target Field was constructed at a cost of $544.4 million (including site acquisition and infrastructure), utilizing the proceeds of a $392 million public bond offering based on a 0.15% sales tax in Hennepin County and private financing of $185 million provided by the Pohlad family. As part of the deal, the Twins also signed a 30-year lease of the new stadium, effectively guaranteeing the continuation of the team in Minnesota for a long time to come. | wiki:25700005 |
Minnesota Twins | Target Field | Construction of the new field began in 2007, and was completed in December 2009, in time for the 2010 season. Commissioner Bud Selig, who earlier had threatened to disband the team, observed that without the new stadium the Twins could not have committed to sign their star player, catcher Joe Mauer, to an 8-year, $184 million contract extension. The first regular season game in Target Field was played against the Boston Red Sox on April 12, 2010, with Mauer driving in two runs and going 3-for-5 to help the Twins defeat the Red Sox, 5–2. On May 18, 2011, Target Field was named "The Best Place To Shop" by Street and Smith's "SportsBusiness Journal" at the magazine's 2011 Sports Business Awards Ceremony in New York City. | wiki:25700006 |
Minnesota Twins | Target Field | It was also named "The Best Sports Stadium in North America" by "ESPN The Magazine" in a ranking that included over 120 different stadiums, ballparks and arenas from around North America. In July 2014, Target Field hosted the 85th Major League Baseball All-Star Game and the Home Run Derby. | wiki:25700007 |
Minnesota Twins | Current | The Twins' white home uniform, first used in 2016, features the current "Twins" script (with an underline below "win") in navy outlined in red with Kasota gold drop shadows. Letters and numerals also take on the same color as the "Twins" script. The modern "Minnie and Paul" alternate logo (with the state of Minnesota in navy outlined in Kasota gold) appears on the left sleeve. Caps are in all-navy with the interlocking "TC" outlined in Kasota gold. The Twins' red alternate home uniform, first used in 2016, features the "TC" insignia outlined in Kasota gold on the left chest. Letters and numerals are in navy outlined in white with Kasota gold drop shadows. | wiki:25700008 |
Minnesota Twins | Current | The "Minnie and Paul" alternate logo appears on the left sleeve. The uniform is paired with a navy-brimmed red cap with the "TC" outlined in Kasota gold. The Twins' navy alternate home uniform, first used in 2019, features the classic "Twins" script (with a tail underline accent after the letter "s") in red outlined in navy and Kasota gold. Letters and numerals also take on the same color as the "Twins" script. As with the home white uniforms, it is paired with the all-navy Kasota gold "TC" cap. The gold-trimmed "TC" insignia also appears on the left sleeve. | wiki:25700009 |
Minnesota Twins | Past uniforms | From 1961 to 1971 the Twins sported uniforms bearing the classic "Twins" script and numerals in navy outlined in red. The original "Minnie and Paul" alternate logo appears on the left sleeve of both the pinstriped white home uniform and grey road uniform. For the 1972 season the Twins updated their uniforms. The color scheme on the "Twins" script and numerals were reversed, pinstripes were removed from the home uniform, and an updated "Minnie and Paul" roundel patch replaced the originals on the left sleeve. In 1973 the Twins switched to polyester pullover uniforms, which included a powder blue road uniform. | wiki:25700010 |
Minnesota Twins | Past uniforms | Chest numerals were added while a navy-brimmed red cap was used with the home uniform. The original "Minnie and Paul" logo returned to the left sleeve. Player names in red were added to the road uniform in 1977. | wiki:25700011 |
Minnesota Twins | Roster | Minnesota Twins all-time roster: A complete list of players who played in at least one game for the Twins franchise. | wiki:25700012 |
Minnesota Twins | Minor league affiliates | The Minnesota Twins farm system consists of six minor league affiliates. | wiki:25700013 |
Minnesota Twins | Baseball Hall of Fame members | Molitor, Morris, and Winfield were all St. Paul natives who joined the Twins late in their careers and were warmly received as "hometown heroes", but were elected to the hall primarily on the basis of their tenures with other teams. Both Molitor and Winfield had their 3,000th hit with Minnesota, while Morris pitched a complete-game shutout for the Twins in game seven of the 1991 World Series. Molitor was the first player in history to hit a triple for his 3,000th hit. Cronin, Goslin, Griffith, Harris, Johnson, Killebrew and Wynn are listed on the Washington Hall of Stars display at Nationals Park (previously they were listed at Robert F. | wiki:25700014 |
Minnesota Twins | Baseball Hall of Fame members | Kennedy Stadium). So are Ossie Bluege, George Case, Joe Judge, George Selkirk, Roy Sievers, Cecil Travis, Mickey Vernon and Eddie Yost. | wiki:25700015 |
Minnesota Twins | Retired numbers | The Metrodome's upper deck in center and right fields was partly covered by a curtain containing banners of various titles won, and retired numbers. There was no acknowledgment of the Twins' prior championships in Washington and several Senator Hall of Famers, such as Walter Johnson, played in the days prior to numbers being used on uniforms. However Killebrew played seven seasons as a Senator, including two full seasons as a regular prior to the move to Minnesota in 1961. Prior to the addition of the banners, the Twins acknowledged their retired numbers on the Metrodome's outfield fence. Harmon Killebrew's #3 was the first to be displayed, as it was the only one the team had retired when they moved in. | wiki:25700016 |
Minnesota Twins | Retired numbers | It was joined by Rod Carew's #29 in 1987, Tony Oliva's #6 in 1991, Kent Hrbek's #14 in 1995, and Kirby Puckett's #34 in 1997 before the Twins began hanging the banners to reduce capacity. The championships, meanwhile were marked on the "Baggie" in right field. The numbers that have been retired hang within Target Field in front of the tower that serves as the Twins' executive offices in left field foul territory. The championships banners have been replaced by small pennants that fly on masts at the back of the left field upper deck. Those pennants, along with the flags flying in the plaza behind right field, serve as a visual cue for the players, suggesting the wind direction and speed. | wiki:25700017 |
Minnesota Twins | Radio and television | In 2007, the Twins took the rights to the broadcasts in-house and created the Twins Radio Network (TRN). With that new network in place the Twins secured a new Metro Affiliate flagship radio station in KSTP (AM 1500). It replaced WCCO (AM 830), which held broadcast rights for the Twins since the team moved to Minneapolis in 1961. For 2013, the Twins moved to FM radio on KTWN-FM "96.3 K-Twin", which is owned by the Pohlad family. The original radio voices of the Twins in 1961 were Ray Scott, Halsey Hall and Bob Wolff. After the first season, Herb Carneal replaced Wolff. | wiki:25700018 |
Minnesota Twins | Radio and television | Twins TV and radio broadcasts were originally sponsored by the Hamm's Brewing Company. In 2009, Treasure Island Resort & Casino became the first ever naming rights partner for the Twins Radio Network, making the commercial name of TRN the Treasure Island Baseball Network. In 2017, it was announced that WCCO would become the flagship station the Twins again starting in 2018, thus returning the team back to its original station after 11 years. Cory Provus is the current radio play by play announcer, taking over in 2012 for longtime Twins voice John Gordon who retired following the 2011 season. Former Twins OF Dan Gladden serves as color commentator. | wiki:25700019 |
Minnesota Twins | Radio and television | TRN broadcasts are originated from the studios at Minnesota News Network and Minnesota Farm Networks. Kris Atteberry hosts the pre-game show, the "Lineup Card" and the "Post-game Download" from those studios except when filling in for Provus or Gladden when they are on vacation. | wiki:25700020 |
Minnesota Twins | Team and franchise traditions | Fans wave a "Homer Hanky" to rally the team during play-offs and other crucial games. The Homer Hanky was created by Terrie Robbins of the Star Tribune newspaper in the Twin Cities in 1987. It was her idea to originally give away 60,000 inaugural Homer Hankies. That year, over 2.3 million Homer Hankies were distributed. The party atmosphere of the Twins clubhouse after a win is well-known, the team's players unwinding with loud rock music (usually the choice of the winning pitcher) and video games. The club has several hazing rituals, such as requiring the most junior relief pitcher on the team to carry water and snacks to the bullpen in a brightly colored small child's backpack (Barbie in 2005, SpongeBob SquarePants in 2006, Hello Kitty in 2007, Disney Princess and Tinkerbell in 2009, Chewbacca and Darth Vader in 2010), and many of its players, both past and present, are notorious pranksters. | wiki:25700021 |
Minnesota Twins | Team and franchise traditions | For example, Bert Blyleven earned the nickname "The Frying Dutchman" for his ability to pull the "hotfoot" – which entails crawling under the bench in the dugout and lighting a teammate's shoelaces on fire. | wiki:25700022 |
Mach number | Introduction | Mach number (M or Ma) (; ) is a dimensionless quantity in fluid dynamics representing the ratio of flow velocity past a boundary to the local speed of sound. where: By definition, at Mach1, the local flow velocity is equal to the speed of sound. At Mach0.65, is 65% of the speed of sound (subsonic), and, at Mach1.35, is 35% faster than the speed of sound (supersonic). Pilots of high-altitude aerospace vehicles use flight Mach number to express a vehicle's true airspeed, but the flow field around a vehicle varies in three dimensions, with corresponding variations in local Mach number. | wiki:25700023 |
Mach number | Overview | Mach number is a measure of the compressibility characteristics of fluid flow: the fluid (air) behaves under the influence of compressibility in a similar manner at a given Mach number, regardless of other variables. As modeled in the International Standard Atmosphere, dry air at mean sea level, standard temperature of , the speed of sound is . The speed of sound is not a constant; in a gas, it increases proportionally to the square root of the absolute temperature, and since atmospheric temperature generally decreases with increasing altitude between sea level and , the speed of sound also decreases. For example, the standard atmosphere model lapses temperature to at altitude, with a corresponding speed of sound (Mach1) of , 86.7% of the sea level value. | wiki:25700024 |
Mach number | Classification of Mach regimes | While the terms "subsonic" and "supersonic", in the purest sense, refer to speeds below and above the local speed of sound respectively, aerodynamicists often use the same terms to talk about particular ranges of Mach values. This occurs because of the presence of a "transonic regime" around flight (free stream) M = 1 where approximations of the Navier-Stokes equations used for subsonic design no longer apply; the simplest explanation is that the flow around an airframe locally begins to exceed M = 1 even though the free stream Mach number is below this value. Meanwhile, the "supersonic regime" is usually used to talk about the set of Mach numbers for which linearised theory may be used, where for example the (air) flow is not chemically reacting, and where heat-transfer between air and vehicle may be reasonably neglected in calculations. | wiki:25700025 |
Mach number | Classification of Mach regimes | In the following table, the "regimes" or "ranges of Mach values" are referred to, and not the "pure" meanings of the words "subsonic" and "supersonic". | wiki:25700026 |
Mach number | High-speed flow around objects | Flight can be roughly classified in six categories: For comparison: the required speed for low Earth orbit is approximately 7.5 km/s = Mach 25.4 in air at high altitudes. At transonic speeds, the flow field around the object includes both sub- and supersonic parts. The transonic period begins when first zones of M > 1 flow appear around the object. In case of an airfoil (such as an aircraft's wing), this typically happens above the wing. Supersonic flow can decelerate back to subsonic only in a normal shock; this typically happens before the trailing edge. (Fig.1a) | wiki:25700027 |
Mach number | High-speed flow in a channel | As a flow in a channel becomes supersonic, one significant change takes place. The conservation of mass flow rate leads one to expect that contracting the flow channel would increase the flow speed (i.e. making the channel narrower results in faster air flow) and at subsonic speeds this holds true. However, once the flow becomes supersonic, the relationship of flow area and speed is reversed: expanding the channel actually increases the speed. The obvious result is that in order to accelerate a flow to supersonic, one needs a convergent-divergent nozzle, where the converging section accelerates the flow to sonic speeds, and the diverging section continues the acceleration. | wiki:25700028 |
Mach number | High-speed flow in a channel | Such nozzles are called de Laval nozzles and in extreme cases they are able to reach hypersonic speeds ( at 20 °C). An aircraft Machmeter or electronic flight information system (EFIS) can display Mach number derived from stagnation pressure (pitot tube) and static pressure. | wiki:25700029 |
Mach number | Calculation | The Mach number at which an aircraft is flying can be calculated by where: Note that the dynamic pressure can be found as: | wiki:25700030 |
Mach number | Calculating Mach number from pitot tube pressure | Mach number is a function of temperature and true airspeed. Aircraft flight instruments, however, operate using pressure differential to compute Mach number, not temperature. Assuming air to be an ideal gas, the formula to compute Mach number in a subsonic compressible flow is found from Bernoulli's equation for (above): The formula to compute Mach number in a supersonic compressible flow can be found from the Rayleigh supersonic pitot equation (above) using parameters for air: | wiki:25700031 |
Moving Picture Experts Group | Introduction | The Moving Picture Experts Group (MPEG) is a working group of authorities that was formed by ISO and IEC to set standards for audio and video compression and transmission. MPEG is officially a collection of ISO Working Groups and Advisory Groups under ISO/IEC JTC 1/SC 29 – "Coding of audio, picture, multimedia and hypermedia information" (ISO/IEC Joint Technical Committee 1, Subcommittee 29). | wiki:25700032 |
Moving Picture Experts Group | History | MPEG was established in 1988 by the initiative of Hiroshi Yasuda (Nippon Telegraph and Telephone) and Leonardo Chiariglione, group Chair from its inception. The first MPEG meeting was in May 1988 in Ottawa, Canada. As of late 2005, MPEG has grown to include approximately 350 members per meeting from various industries, universities, and research institutions. On June 6, 2020, the MPEG website – hosted by Chiariglione – was updated to inform readers that he retired as convenor, and that the MPEG group "was closed". Chiariglione, in his own blog, explained his reasons for deciding to step down. The decision followed a restructuring process within SC 29, in which "some of the subgroups of WG 11 (MPEG) will become distinct MPEG working groups (WGs) and advisory groups (AGs)" in July 2020. | wiki:25700033 |
Moving Picture Experts Group | History | In the interim, Prof. Jörn Ostermann has been appointed as Acting Convenor of SC 29/WG 11. | wiki:25700034 |
Moving Picture Experts Group | Joint Video Team | Joint Video Team (JVT) is joint project between ITU-T SG16/Q.6 (Study Group 16 / Question 6) – VCEG (Video Coding Experts Group) and ISO/IEC JTC 1/SC 29/WG 11 – MPEG for the development of new video coding recommendation and international standard. It was formed in 2001 and its main result has been H.264/MPEG-4 AVC (MPEG-4 Part 10). | wiki:25700035 |
Moving Picture Experts Group | Joint Collaborative Team on Video Coding | Joint Collaborative Team on Video Coding (JCT-VC) is a group of video coding experts from ITU-T Study Group 16 (VCEG) and ISO/IEC JTC 1/SC 29/WG 11 (MPEG). It was created in 2010 to develop High Efficiency Video Coding, a new generation video coding standard that further reduces (by 50%) the data rate required for high quality video coding, as compared to the current ITU-T H.264 / ISO/IEC 14496-10 standard. JCT-VC is co-chaired by Jens-Rainer Ohm and Gary Sullivan. | wiki:25700036 |
Moving Picture Experts Group | Joint Video Exploration Team | Joint Video Exploration Team (JVET) is a joint group of video coding experts from ITU-T Study Group 16 (VCEG) and ISO/IEC JTC 1/SC 29/WG 11 (MPEG) created in 2017 after an exploration phase in 2015. It seeks to develop Versatile Video Coding (VVC). Like JCT-VC, JVET is co-chaired by Jens-Rainer Ohm and Gary Sullivan. | wiki:25700037 |
Moving Picture Experts Group | Standards | The MPEG standards consist of different "Parts". Each "part" covers a certain aspect of the whole specification. The standards also specify "Profiles" and "Levels". "Profiles" are intended to define a set of tools that are available, and "Levels" define the range of appropriate values for the properties associated with them. Some of the approved MPEG standards were revised by later amendments and/or new editions. MPEG has standardized the following compression formats and ancillary standards. All of the MPEG formats listed below use discrete cosine transform (DCT) based lossy video compression algorithms. MPEG-4 has been chosen as the compression scheme for over-the-air in Brazil (ISDB-TB), based on original digital television from Japan (ISDB-T). | wiki:25700038 |
Moving Picture Experts Group | Standardization process | A standard published by ISO/IEC is the last stage of a long process that starts with the proposal of new work within a committee. Here are some abbreviations used for marking a standard with its status: Other abbreviations: A proposal of work (New Proposal) is approved at Subcommittee and then at the Technical Committee level (SC29 and JTC1 respectively – in the case of MPEG). When the scope of new work is sufficiently clarified, MPEG usually makes open requests for proposals – known as "Call for proposals". The first document that is produced for audio and video coding standards is called a Verification Model (VM). | wiki:25700039 |
Moving Picture Experts Group | Standardization process | In the case of MPEG-1 and MPEG-2 this was called Simulation and Test Model, respectively. When a sufficient confidence in the stability of the standard under development is reached, a Working Draft (WD) is produced. This is in the form of a standard but is kept internal to MPEG for revision. When a WD is sufficiently solid, becomes Committee Draft (CD) (usually at the planned time). It is then sent to National Bodies (NB) for ballot. The CD becomes Final Committee Draft (FCD) if the number of positive votes is above the quorum. After a review and comments issued by NBs, FCD is again submitted to NBs for the second ballot. | wiki:25700040 |
Moving Picture Experts Group | Standardization process | If the FCD is approved, it becomes Final Draft International Standard (FDIS). ISO then holds a ballot with National Bodies, where no technical changes are allowed (yes/no ballot). If approved, the document becomes International Standard (IS). | wiki:25700041 |
MPEG-1 | Introduction | 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 (26:1 and 6:1 compression ratios respectively) without excessive quality loss, making video CDs, digital cable/satellite TV and digital audio broadcasting (DAB) possible. Today, MPEG-1 has become the most widely compatible lossy audio/video format in the world, and is used in a large number of products and technologies. Perhaps the best-known part of the MPEG-1 standard is the first version of the MP3 audio format it introduced. The MPEG-1 standard is published as ISO/IEC 11172 – Information technology—Coding of moving pictures and associated audio for digital storage media at up to about 1.5 Mbit/s. | wiki:25700042 |
MPEG-1 | Introduction | The standard consists of the following five "Parts": | wiki:25700043 |
MPEG-1 | History | The predecessor of MPEG-1 for video coding was the H.261 standard produced by the CCITT (now known as the ITU-T). The basic architecture established in H.261 was the motion-compensated DCT hybrid video coding structure. It uses macroblocks of size 16×16 with block-based motion estimation in the encoder and motion compensation using encoder-selected motion vectors in the decoder, with residual difference coding using a discrete cosine transform (DCT) of size 8×8, scalar quantization, and variable-length codes (like Huffman codes) for entropy coding. H.261 was the first practical video coding standard, and all of its described design elements were also used in MPEG-1. | wiki:25700044 |
MPEG-1 | History | Modeled on the successful collaborative approach and the compression technologies developed by the Joint Photographic Experts Group and CCITT's Experts Group on Telephony (creators of the JPEG image compression standard and the H.261 standard for video conferencing respectively), the Moving Picture Experts Group (MPEG) working group was established in January 1988, by the initiative of Hiroshi Yasuda (Nippon Telegraph and Telephone) and Leonardo Chiariglione (CSELT). MPEG was formed to address the need for standard video and audio formats, and to build on H.261 to get better quality through the use of somewhat more complex encoding methods (e.g., supporting higher precision for motion vectors). | wiki:25700045 |
MPEG-1 | History | Development of the MPEG-1 standard began in May 1988. Fourteen video and fourteen audio codec proposals were submitted by individual companies and institutions for evaluation. The codecs were extensively tested for computational complexity and subjective (human perceived) quality, at data rates of 1.5 Mbit/s. This specific bitrate was chosen for transmission over T-1/E-1 lines and as the approximate data rate of audio CDs. The codecs that excelled in this testing were utilized as the basis for the standard and refined further, with additional features and other improvements being incorporated in the process. | wiki:25700046 |
MPEG-1 | Patents | Due to its age, MPEG-1 is no longer covered by any essential patents and can thus be used without obtaining a licence or paying any fees. The ISO patent database lists one patent for ISO 11172, US 4,472,747, which expired in 2003. The near-complete draft of the MPEG-1 standard was publicly available as ISO CD 11172 by December 6, 1991. Neither the July 2008 Kuro5hin article "Patent Status of MPEG-1, H.261 and MPEG-2", nor an August 2008 thread on the gstreamer-devel mailing list were able to list a single unexpired MPEG-1 Video and MPEG-1 Audio Layer I/II patent. A May 2009 discussion on the whatwg mailing list mentioned US 5,214,678 patent as possibly covering MPEG-1 Audio Layer II. | wiki:25700047 |
MPEG-1 | Patents | Filed in 1990 and published in 1993, this patent is now expired. A full MPEG-1 decoder and encoder, with "Layer III audio", could not be implemented royalty free since there were companies that required patent fees for implementations of MPEG-1 Audio Layer III, as discussed in the MP3 article. All patents in the world connected to MP3 expired 30 December 2017, which makes this format totally free for use. On 23 April 2017, Fraunhofer IIS stopped charging for Technicolor's MP3 licensing program for certain MP3 related patents and software. | wiki:25700048 |
MPEG-1 | Former patent holders | The following corporations filed declarations with ISO saying they held patents for the MPEG-1 Video (ISO/IEC-11172-2) format, although all such patents have since expired. | wiki:25700049 |
MPEG-1 | Part 1: Systems | Part 1 of the MPEG-1 standard covers "systems", and is defined in ISO/IEC-11172-1. MPEG-1 Systems specifies the logical layout and methods used to store the encoded audio, video, and other data into a standard bitstream, and to maintain synchronization between the different contents. This file format is specifically designed for storage on media, and transmission over communication channels, that are considered relatively reliable. Only limited error protection is defined by the standard, and small errors in the bitstream may cause noticeable defects. This structure was later named an MPEG program stream: "The MPEG-1 Systems design is essentially identical to the MPEG-2 Program Stream structure." This terminology is more popular, precise (differentiates it from an MPEG transport stream) and will be used here. | wiki:25700050 |
MPEG-1 | Program streams | Program Streams (PS) are concerned with combining multiple packetized elementary streams (usually just one audio and video PES) into a single stream, ensuring simultaneous delivery, and maintaining synchronization. The PS structure is known as a multiplex, or a container format. Presentation time stamps (PTS) exist in PS to correct the inevitable disparity between audio and video SCR values (time-base correction). 90 kHz PTS values in the PS header tell the decoder which video SCR values match which audio SCR values. PTS determines when to display a portion of an MPEG program, and is also used by the decoder to determine when data can be discarded from the buffer. | wiki:25700051 |
MPEG-1 | Program streams | Either video or audio will be delayed by the decoder until the corresponding segment of the other arrives and can be decoded. PTS handling can be problematic. Decoders must accept multiple "program streams" that have been concatenated (joined sequentially). This causes PTS values in the middle of the video to reset to zero, which then begin incrementing again. Such PTS wraparound disparities can cause timing issues that must be specially handled by the decoder. | wiki:25700052 |
MPEG-1 | Multiplexing | To generate the PS, the multiplexer will interleave the (two or more) packetized elementary streams. This is done so the packets of the simultaneous streams can be transferred over the same channel and are guaranteed to both arrive at the decoder at precisely the same time. This is a case of time-division multiplexing. Determining how much data from each stream should be in each interleaved segment (the size of the interleave) is complicated, yet an important requirement. Improper interleaving will result in buffer underflows or overflows, as the receiver gets more of one stream than it can store (e.g. audio), before it gets enough data to decode the other simultaneous stream (e.g. | wiki:25700053 |
MPEG-1 | Multiplexing | video). The MPEG Video Buffering Verifier (VBV) assists in determining if a multiplexed PS can be decoded by a device with a specified data throughput rate and buffer size. This offers feedback to the muxer and the encoder, so that they can change the mux size or adjust bitrates as needed for compliance. | wiki:25700054 |
MPEG-1 | Part 2: Video | Part 2 of the MPEG-1 standard covers video and is defined in ISO/IEC-11172-2. The design was heavily influenced by H.261. MPEG-1 Video exploits perceptual compression methods to significantly reduce the data rate required by a video stream. It reduces or completely discards information in certain frequencies and areas of the picture that the human eye has limited ability to fully perceive. It also exploits temporal (over time) and spatial (across a picture) redundancy common in video to achieve better data compression than would be possible otherwise. (See: Video compression) | wiki:25700055 |
MPEG-1 | Color space | Before encoding video to MPEG-1, the color-space is transformed to Y′CbCr (Y′=Luma, Cb=Chroma Blue, Cr=Chroma Red). Luma (brightness, resolution) is stored separately from chroma (color, hue, phase) and even further separated into red and blue components. The chroma is also subsampled to , meaning it is reduced to half resolution vertically and half resolution horizontally, i.e., to just one quarter the number of samples used for the luma component of the video. This use of higher resolution for some color components is similar in concept to the Bayer pattern filter that is commonly used for the image capturing sensor in digital color cameras. | wiki:25700056 |
MPEG-1 | Color space | Because the human eye is much more sensitive to small changes in brightness (the Y component) than in color (the Cr and Cb components), chroma subsampling is a very effective way to reduce the amount of video data that needs to be compressed. However, on videos with fine detail (high spatial complexity) this can manifest as chroma aliasing artifacts. Compared to other digital compression artifacts, this issue seems to very rarely be a source of annoyance. Because of the subsampling, Y′CbCr 4:2:0 video is ordinarily stored using even dimensions (divisible by 2 horizontally and vertically). Y′CbCr color is often informally called YUV to simplify the notation, although that term more properly applies to a somewhat different color format. | wiki:25700057 |
MPEG-1 | Color space | Similarly, the terms luminance and chrominance are often used instead of the (more accurate) terms luma and chroma. | wiki:25700058 |
MPEG-1 | Resolution/bitrate | MPEG-1 supports resolutions up to 4095×4095 (12 bits), and bit rates up to 100 Mbit/s. MPEG-1 videos are most commonly seen using Source Input Format (SIF) resolution: 352×240, 352×288, or 320×240. These relatively low resolutions, combined with a bitrate less than 1.5 Mbit/s, make up what is known as a constrained parameters bitstream (CPB), later renamed the "Low Level" (LL) profile in MPEG-2. This is the minimum video specifications any decoder should be able to handle, to be considered MPEG-1 compliant. This was selected to provide a good balance between quality and performance, allowing the use of reasonably inexpensive hardware of the time. | wiki:25700059 |
MPEG-1 | Frame/picture/block types | MPEG-1 has several frame/picture types that serve different purposes. The most important, yet simplest, is I-frame. | wiki:25700060 |
MPEG-1 | I-frames | "I-frame" is an abbreviation for "Intra-frame", so-called because they can be decoded independently of any other frames. They may also be known as I-pictures, or keyframes due to their somewhat similar function to the key frames used in animation. I-frames can be considered effectively identical to baseline JPEG images. High-speed seeking through an MPEG-1 video is only possible to the nearest I-frame. When cutting a video it is not possible to start playback of a segment of video before the first I-frame in the segment (at least not without computationally intensive re-encoding). For this reason, I-frame-only MPEG videos are used in editing applications. | wiki:25700061 |
MPEG-1 | I-frames | I-frame only compression is very fast, but produces very large file sizes: a factor of 3× (or more) larger than normally encoded MPEG-1 video, depending on how temporally complex a specific video is. I-frame only MPEG-1 video is very similar to MJPEG video. So much so that very high-speed and theoretically lossless (in reality, there are rounding errors) conversion can be made from one format to the other, provided a couple of restrictions (color space and quantization matrix) are followed in the creation of the bitstream. | wiki:25700062 |
MPEG-1 | P-frames | "P-frame" is an abbreviation for "Predicted-frame". They may also be called forward-predicted frames or inter-frames (B-frames are also inter-frames). P-frames exist to improve compression by exploiting the temporal (over time) redundancy in a video. P-frames store only the "difference" in image from the frame (either an I-frame or P-frame) immediately preceding it (this reference frame is also called the "anchor frame"). The difference between a P-frame and its anchor frame is calculated using "motion vectors" on each "macroblock" of the frame (see below). Such motion vector data will be embedded in the P-frame for use by the decoder. | wiki:25700063 |
MPEG-1 | B-frames | "B-frame" stands for "bidirectional-frame" or "bipredictive frame". They may also be known as backwards-predicted frames or B-pictures. B-frames are quite similar to P-frames, except they can make predictions using both the previous and future frames (i.e. two anchor frames). It is therefore necessary for the player to first decode the next I- or P- anchor frame sequentially after the B-frame, before the B-frame can be decoded and displayed. This means decoding B-frames requires larger data buffers and causes an increased delay on both decoding and during encoding. This also necessitates the decoding time stamps (DTS) feature in the container/system stream (see above). | wiki:25700064 |
MPEG-1 | B-frames | As such, B-frames have long been subject of much controversy, they are often avoided in videos, and are sometimes not fully supported by hardware decoders. No other frames are predicted from a B-frame. Because of this, a very low bitrate B-frame can be inserted, where needed, to help control the bitrate. If this was done with a P-frame, future P-frames would be predicted from it and would lower the quality of the entire sequence. However, similarly, the future P-frame must still encode all the changes between it and the previous I- or P- anchor frame. B-frames can also be beneficial in videos where the background behind an object is being revealed over several frames, or in fading transitions, such as scene changes. | wiki:25700065 |
MPEG-1 | D-frames | MPEG-1 has a unique frame type not found in later video standards. "D-frames" or DC-pictures are independently coded images (intra-frames) that have been encoded using DC transform coefficients only (AC coefficients are removed when encoding D-frames—see DCT below) and hence are very low quality. D-frames are never referenced by I-, P- or B- frames. D-frames are only used for fast previews of video, for instance when seeking through a video at high speed. Given moderately higher-performance decoding equipment, fast preview can be accomplished by decoding I-frames instead of D-frames. This provides higher quality previews, since I-frames contain AC coefficients as well as DC coefficients. | wiki:25700066 |
MPEG-1 | D-frames | If the encoder can assume that rapid I-frame decoding capability is available in decoders, it can save bits by not sending D-frames (thus improving compression of the video content). For this reason, D-frames are seldom actually used in MPEG-1 video encoding, and the D-frame feature has not been included in any later video coding standards. | wiki:25700067 |
MPEG-1 | Macroblocks | MPEG-1 operates on video in a series of 8×8 blocks for quantization. However, to reduce the bit rate needed for motion vectors and because chroma (color) is subsampled by a factor of 4, each pair of (red and blue) chroma blocks corresponds to 4 different luma blocks. This set of 6 blocks, with a resolution of 16×16, is processed together and called a "macroblock". A macroblock is the smallest independent unit of (color) video. Motion vectors (see below) operate solely at the macroblock level. If the height or width of the video are not exact multiples of 16, full rows and full columns of macroblocks must still be encoded and decoded to fill out the picture (though the extra decoded pixels are not displayed). | wiki:25700068 |
MPEG-1 | Motion vectors | To decrease the amount of temporal redundancy in a video, only blocks that change are updated, (up to the maximum GOP size). This is known as conditional replenishment. However, this is not very effective by itself. Movement of the objects, and/or the camera may result in large portions of the frame needing to be updated, even though only the position of the previously encoded objects has changed. Through motion estimation, the encoder can compensate for this movement and remove a large amount of redundant information. The encoder compares the current frame with adjacent parts of the video from the anchor frame (previous I- or P- frame) in a diamond pattern, up to a (encoder-specific) predefined radius limit from the area of the current macroblock. | wiki:25700069 |
MPEG-1 | Motion vectors | If a match is found, only the direction and distance (i.e. the "vector" of the "motion") from the previous video area to the current macroblock need to be encoded into the inter-frame (P- or B- frame). The reverse of this process, performed by the decoder to reconstruct the picture, is called motion compensation. A predicted macroblock rarely matches the current picture perfectly, however. The differences between the estimated matching area, and the real frame/macroblock is called the prediction error. The larger the amount of prediction error, the more data must be additionally encoded in the frame. For efficient video compression, it is very important that the encoder is capable of effectively and precisely performing motion estimation. | wiki:25700070 |
MPEG-1 | DCT | Each 8×8 block is encoded by first applying a "forward" discrete cosine transform (FDCT) and then a quantization process. The FDCT process (by itself) is theoretically lossless, and can be reversed by applying an "Inverse" DCT (IDCT) to reproduce the original values (in the absence of any quantization and rounding errors). In reality, there are some (sometimes large) rounding errors introduced both by quantization in the encoder (as described in the next section) and by IDCT approximation error in the decoder. The minimum allowed accuracy of a decoder IDCT approximation is defined by ISO/IEC 23002-1. (Prior to 2006, it was specified by IEEE 1180-1990.) The FDCT process converts the 8×8 block of uncompressed pixel values (brightness or color difference values) into an 8×8 indexed array of "frequency coefficient" values. | wiki:25700071 |
MPEG-1 | DCT | One of these is the (statistically high in variance) "DC coefficient", which represents the average value of the entire 8×8 block. The other 63 coefficients are the statistically smaller "AC coefficients", which have positive or negative values each representing sinusoidal deviations from the flat block value represented by the DC coefficient. An example of an encoded 8×8 FDCT block: | wiki:25700072 |
MPEG-1 | Quantization | Quantization is, essentially, the process of reducing the accuracy of a signal, by dividing it by some larger step size and rounding to an integer value (i.e. finding the nearest multiple, and discarding the remainder). The frame-level quantizer is a number from 0 to 31 (although encoders will usually omit/disable some of the extreme values) which determines how much information will be removed from a given frame. The frame-level quantizer is typically either dynamically selected by the encoder to maintain a certain user-specified bitrate, or (much less commonly) directly specified by the user. A "quantization matrix" is a string of 64 numbers (ranging from 0 to 255) which tells the encoder how relatively important or unimportant each piece of visual information is. | wiki:25700073 |
MPEG-1 | Quantization | Each number in the matrix corresponds to a certain frequency component of the video image. | wiki:25700074 |
MPEG-1 | Entropy coding | Several steps in the encoding of MPEG-1 video are lossless, meaning they will be reversed upon decoding, to produce exactly the same (original) values. Since these lossless data compression steps don't add noise into, or otherwise change the contents (unlike quantization), it is sometimes referred to as noiseless coding. Since lossless compression aims to remove as much redundancy as possible, it is known as entropy coding in the field of information theory. The coefficients of quantized DCT blocks tend to zero towards the bottom-right. Maximum compression can be achieved by a zig-zag scanning of the DCT block starting from the top left and using Run-length encoding techniques. | wiki:25700075 |
MPEG-1 | Entropy coding | The DC coefficients and motion vectors are DPCM-encoded. | wiki:25700076 |
MPEG-1 | GOP configurations for specific applications | I-frames store complete frame info within the frame and are therefore suited for random access. P-frames provide compression using motion vectors relative to the previous frame ( I or P ). B-frames provide maximum compression but require the previous as well as next frame for computation. Therefore, processing of B-frames requires more buffer on the decoded side. A configuration of the Group of Pictures (GOP) should be selected based on these factors. I-frame only sequences give least compression, but are useful for random access, FF/FR and editability. I- and P-frame sequences give moderate compression but add a certain degree of random access, FF/FR functionality. | wiki:25700077 |
MPEG-1 | GOP configurations for specific applications | I-, P- and B-frame sequences give very high compression but also increase the coding/decoding delay significantly. Such configurations are therefore not suited for video-telephony or video-conferencing applications. The typical data rate of an I-frame is 1 bit per pixel while that of a P-frame is 0.1 bit per pixel and for a B-frame, 0.015 bit per pixel. | wiki:25700078 |
MPEG-1 | Part 3: Audio | Part 3 of the MPEG-1 standard covers audio and is defined in ISO/IEC-11172-3. MPEG-1 Audio utilizes psychoacoustics to significantly reduce the data rate required by an audio stream. It reduces or completely discards certain parts of the audio that it deduces that the human ear can't "hear", either because they are in frequencies where the ear has limited sensitivity, or are "masked" by other (typically louder) sounds. Channel Encoding: | wiki:25700079 |
MPEG-1 | Layer I | MPEG-1 Audio Layer I is a simplified version of MPEG-1 Audio Layer II. Layer I uses a smaller 384-sample frame size for very low delay, and finer resolution. This is advantageous for applications like teleconferencing, studio editing, etc. It has lower complexity than Layer II to facilitate real-time encoding on the hardware available circa 1990. Layer I saw limited adoption in its time, and most notably was used on Philips' defunct Digital Compact Cassette at a bitrate of 384 kbit/s. With the substantial performance improvements in digital processing since its introduction, Layer I quickly became unnecessary and obsolete. Layer I audio files typically use the extension ".mp1" or sometimes ".m1a". | wiki:25700080 |
MPEG-1 | Layer II | MPEG-1 Audio Layer II (the first version of MP2, often informally called MUSICAM) is a lossy audio format designed to provide high quality at about 192 kbit/s for stereo sound. Decoding MP2 audio is computationally simple relative to MP3, AAC, etc. | wiki:25700081 |
MPEG-1 | History/MUSICAM | MPEG-1 Audio Layer II was derived from the MUSICAM ("Masking pattern adapted Universal Subband Integrated Coding And Multiplexing") audio codec, developed by Centre commun d'études de télévision et télécommunications (CCETT), Philips, and Institut für Rundfunktechnik (IRT/CNET) as part of the EUREKA 147 pan-European inter-governmental research and development initiative for the development of digital audio broadcasting. Most key features of MPEG-1 Audio were directly inherited from MUSICAM, including the filter bank, time-domain processing, audio frame sizes, etc. However, improvements were made, and the actual MUSICAM algorithm was not used in the final MPEG-1 Audio Layer II standard. The widespread usage of the term MUSICAM to refer to Layer II is entirely incorrect and discouraged for both technical and legal reasons. | wiki:25700082 |
MPEG-1 | Technical details | MP3 is a frequency-domain audio transform encoder. Even though it utilizes some of the lower layer functions, MP3 is quite different from MP2. MP3 works on 1152 samples like MP2, but needs to take multiple frames for analysis before frequency-domain (MDCT) processing and quantization can be effective. It outputs a variable number of samples, using a bit buffer to enable this variable bitrate (VBR) encoding while maintaining 1152 sample size output frames. This causes a significantly longer delay before output, which has caused MP3 to be considered unsuitable for studio applications where editing or other processing needs to take place. | wiki:25700083 |
MPEG-1 | Technical details | MP3 does not benefit from the 32 sub-band polyphased filter bank, instead just using an 18-point MDCT transformation on each output to split the data into 576 frequency components, and processing it in the frequency domain. This extra granularity allows MP3 to have a much finer psychoacoustic model, and more carefully apply appropriate quantization to each band, providing much better low-bitrate performance. | wiki:25700084 |
MPEG-1 | Quality | These technical limitations inherently prevent MP3 from providing critically transparent quality at any bitrate. This makes Layer II sound quality actually superior to MP3 audio, when it is used at a high enough bitrate to avoid noticeable artifacts. The term "transparent" often gets misused, however. The quality of MP3 (and other codecs) is sometimes called "transparent," even at impossibly low bitrates, when what is really meant is "good quality on average/non-critical material," or perhaps "exhibiting only non-annoying artifacts." MP3's more fine-grained and selective quantization does prove notably superior to MP2 at lower-bitrates, however. It is able to provide nearly equivalent audio quality to Layer II, at a 15% lower bitrate (approximately). | wiki:25700085 |
MPEG-1 | Quality | 128 kbit/s is considered the "sweet spot" for MP3; meaning it provides generally acceptable quality stereo sound on most music, and there are diminishing quality improvements from increasing the bitrate further. MP3 is also regarded as exhibiting artifacts that are less annoying than Layer II, when both are used at bitrates that are too low to possibly provide faithful reproduction. Layer III audio files use the extension ".mp3". | wiki:25700086 |
MPEG-1 | Layer III | MPEG-1 Audio Layer III (the first version of MP3) is a lossy audio format designed to provide acceptable quality at about 64 kbit/s for monaural audio over single-channel (BRI) ISDN links, and 128 kbit/s for stereo sound. | wiki:25700087 |
MPEG-1 | History/ASPEC | MPEG-1 Audio Layer III was derived from the "Adaptive Spectral Perceptual Entropy Coding" (ASPEC) codec developed by Fraunhofer as part of the EUREKA 147 pan-European inter-governmental research and development initiative for the development of digital audio broadcasting. ASPEC was adapted to fit in with the Layer II model (frame size, filter bank, FFT, etc.), to become Layer III. ASPEC was itself based on "Multiple adaptive Spectral audio Coding" (MSC) by E. F. Schroeder, "Optimum Coding in the Frequency domain" (OCF) the doctoral thesis by Karlheinz Brandenburg at the University of Erlangen-Nuremberg, "Perceptual Transform Coding" (PXFM) by J. D. Johnston at AT&T Bell Labs, and "Transform coding of audio signals" by Y. | wiki:25700088 |
MPEG-1 | History/ASPEC | Mahieux and J. Petit at Institut für Rundfunktechnik (IRT/CNET). | wiki:25700089 |
MPEG-1 | MPEG-2 audio extensions | The MPEG-2 standard includes several extensions to MPEG-1 Audio. These are known as MPEG-2 BC – backwards compatible with MPEG-1 Audio. MPEG-2 Audio is defined in ISO/IEC 13818-3. These sampling rates are exactly half that of those originally defined for MPEG-1 Audio. They were introduced to maintain higher quality sound when encoding audio at lower-bitrates. The even-lower bitrates were introduced because tests showed that MPEG-1 Audio could provide higher quality than any existing (circa 1994) very low bitrate (i.e. speech) audio codecs. | wiki:25700090 |
MPEG-1 | Part 4: Conformance testing | Part 4 of the MPEG-1 standard covers conformance testing, and is defined in ISO/IEC-11172-4. Conformance: Procedures for testing conformance. Provides two sets of guidelines and reference bitstreams for testing the conformance of MPEG-1 audio and video decoders, as well as the bitstreams produced by an encoder. | wiki:25700091 |
MPEG-1 | Part 5: Reference software | Part 5 of the MPEG-1 standard includes reference software, and is defined in ISO/IEC TR 11172-5. Simulation: Reference software. C reference code for encoding and decoding of audio and video, as well as multiplexing and demultiplexing. | wiki:25700092 |
MPEG-1 | File extension | .mpg is one of a number of file extensions for MPEG-1 or MPEG-2 audio and video compression. MPEG-1 Part 2 video is rare nowadays, and this extension typically refers to an MPEG program stream (defined in MPEG-1 and MPEG-2) or MPEG transport stream (defined in MPEG-2). Other suffixes such as .m2ts also exist specifying the precise container, in this case MPEG-2 TS, but this has little relevance to MPEG-1 media. .mp3 is the most common extension for files containing MP3 audio (typically MPEG-1 Audio, sometimes MPEG-2 Audio). An MP3 file is typically an uncontained stream of raw audio; the conventional way to tag MP3 files is by writing data to "garbage" segments of each frame, which preserve the media information but are discarded by the player. | wiki:25700093 |
MPEG-1 | File extension | This is similar in many respects to how raw .AAC files are tagged (but this is less supported nowadays, e.g. iTunes). Note that although it would apply, .mpg does not normally append raw AAC or AAC in MPEG-2 Part 7 Containers. The .aac extension normally denotes these audio files. | wiki:25700094 |
Mumia Abu-Jamal | Introduction | Mumia Abu-Jamal (born Wesley Cook; April 24, 1954) is a political activist and journalist who was convicted of murder and sentenced to death in 1982 for the 1981 murder of Philadelphia police officer Daniel Faulkner. He became widely known while on death row for his writings and commentary on the criminal justice system in the United States. After numerous appeals, his death penalty sentence was overturned by a Federal court. In 2011, the prosecution agreed to a sentence of life imprisonment without parole. He entered the general prison population early the following year. Beginning at the age of 14 in 1968, Abu-Jamal became involved with the Black Panther Party and was a member until October 1970. | wiki:25700095 |
Mumia Abu-Jamal | Introduction | After he left the party, he completed his high school education, and later became a radio reporter. He eventually served as president of the Philadelphia Association of Black Journalists. He supported the MOVE Organization in Philadelphia and covered the 1978 confrontation in which one police officer was killed. The MOVE Nine were the members who were arrested and convicted of murder in that case. Since 1982, the murder trial of Abu-Jamal has been seriously criticized for constitutional failings; some have claimed that he is innocent, and many opposed his death sentence. The Faulkner family, public authorities, police organizations, and other groups believe that Abu-Jamal's trial was fair, his guilt undeniable, and his death sentence appropriate. | wiki:25700096 |
Mumia Abu-Jamal | Early life and activism | He was born Wesley Cook in Philadelphia, Pennsylvania, where he grew up. He has a younger brother named William. They attended local public schools. In 1968, a high school teacher, a Kenyan instructing a class on African cultures, encouraged the students to take African or Arabic names for classroom use; he gave Cook the name "Mumia". According to Abu-Jamal, "Mumia" means "Prince" and was the name of a Kenyan anti-colonial African nationalist who fought against the British before Kenyan independence. | wiki:25700097 |
Mumia Abu-Jamal | Involvement with the Black Panthers | Abu-Jamal has described being "kicked ... into the Black Panther Party" as a teenager of 14, after suffering a beating from "white racists" and a policeman for trying to disrupt a 1968 rally for Independent candidate George Wallace, former governor of Alabama, who was running on a racist platform. From then he helped form the Philadelphia branch of the Black Panther Party with Defense Captain Reggie Schell, and other Panthers. He was appointed as the chapter's "Lieutenant of Information," responsible for writing information and news communications. In an interview in the early years, Abu-Jamal quoted Mao Zedong, saying that "political power grows out of the barrel of a gun". | wiki:25700098 |
Mumia Abu-Jamal | Involvement with the Black Panthers | That same year, he dropped out of Benjamin Franklin High School and began living at the branch's headquarters. He spent late 1969 in New York City and early 1970 in Oakland, living and working with BPP colleagues in those cities; the party had been founded in Oakland. He was a party member from May 1969 until October 1970. During this period, he was subject to illegal surveillance as part of the Federal Bureau of Investigation's COINTELPRO program, with which the Philadelphia police cooperated. The FBI was working to infiltrate black radical groups and to disrupt them by creating internal dissension. | wiki:25700099 |
Mumia Abu-Jamal | Return to education | After leaving the Panthers, Abu-Jamal returned as a student to his former high school. He was suspended for distributing literature calling for "black revolutionary student power". He led unsuccessful protests to change the school name to Malcolm X High, to honor the major African-American leader who had been killed in New York by political opponents. After attaining his GED, Abu-Jamal studied briefly at Goddard College in rural Vermont. He returned to Philadelphia. | wiki:25700100 |