Misplaced Pages

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47-456: The Ogg container format can multiplex a number of independent streams for audio , video , text (such as subtitles ), and metadata . In the Ogg multimedia framework, Theora provides a lossy video layer. The audio layer is most commonly provided by the music-oriented Vorbis format or its successor Opus . Lossless audio compression formats include FLAC , and OggPCM . Before 2007,

94-644: A Windows Media Player Ogg codec. By June 30, 2009, the Ogg container, through the use of the Theora and Vorbis, was the only container format included in Firefox 3.5 web browser's implementation of the HTML5 <video> and <audio> elements. This was in accordance with the original recommendation outlined in, but later removed from, the HTML5 draft specification (see Ogg controversy ). On March 3, 2010,

141-430: A 10-Mbit line entering a network, STDM can be used to provide 178 terminals with a dedicated 56k connection (178 * 56k = 9.96 Mb). A more common use however is to only grant the bandwidth when that much is needed. STDM does not reserve a time slot for each terminal, rather it assigns a slot when the terminal is requiring data to be sent or received. In its primary form, TDM is used for circuit mode communication with

188-417: A fixed number of channels and constant bandwidth per channel. Bandwidth reservation distinguishes time-division multiplexing from statistical multiplexing such as statistical time-division multiplexing. In pure TDM, the time slots are recurrent in a fixed order and pre-allocated to the channels, rather than scheduled on a packet-by-packet basis. In dynamic TDMA , a scheduling algorithm dynamically reserves

235-408: A packet's length is a multiple of 255, the final segment is length 0. Where the final packet continues on the next page, the final segment value is 255, and the continuation flag is set on the following page to indicate that the start of the new page is a continuation of last page. VorbisComment is a base-level Metadata format initially authored for use with Ogg Vorbis. It has since been adopted in

282-466: A single composition. The specification gives several example tag names such as TITLE and TRACKNUMBER . Most applications also support common de facto standards, such as DISCNUMBER , RATING , and tags for ReplayGain information. Ratings are usually mapped as 1-5 stars with 20,40,60,80,100 as the actual string values. There are no provisions for storing binary data in Vorbis comments. This

329-403: A technical analysis by an FFmpeg developer was critical about the general purpose abilities of Ogg as a multimedia container format. The author of Ogg later responded to these claims in an article of his own. Ogg is only a container format. The actual audio or video encoded by a codec is stored inside an Ogg container. Ogg containers may contain streams encoded with multiple codecs; for example,

376-458: A transmission stream. A standard DS0 voice signal has a data bit rate of 64 kbit/s. A TDM circuit runs at a much higher signal bandwidth, permitting the bandwidth to be divided into time frames (time slots) for each voice signal which is multiplexed onto the line by the transmitter. If the TDM frame consists of n voice frames, the line bandwidth is n *64 kbit/s. Each voice time slot in

423-426: A variable number of time slots in each frame to variable bit-rate data streams, based on the traffic demand of each data stream. Dynamic TDMA is used in: Asynchronous time-division multiplexing (ATDM), is an alternative nomenclature in which STDM designates synchronous time-division multiplexing, the older method that uses fixed time slots. Vorbis comment A Vorbis comment is a metadata container used in

470-446: A video file with sound contains data encoded by both an audio codec and a video codec. Being a container format, Ogg can embed audio and video in various formats (such as Dirac , MNG , CELT , MPEG-4 , MP3 and others) but Ogg was intended to be, and usually is, used with the following Xiph.org free codecs: Ogg audio media is registered as IANA media type audio/ogg with file extensions .oga , .ogg , and .spx . It

517-435: 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 according to agreed rules, e.g. with each transmitter working in turn. 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

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564-465: Is a proper subset of the Ogg video media type video/ogg with file extension .ogv . Other Ogg applications use media type application/ogg with file extension .ogx ; this is a superset of video/ogg . The Opus media type audio/opus with file extension .opus was registered later in RFC 7587 and 7845 . Time-division multiplexing Time-division multiplexing ( TDM )

611-438: Is case insensitive, so artist and ARTIST are the same field. The number of fields and their length is restricted to 4,294,967,295 (the maximum value of an unsigned 32- bit integer ), but most tag editing applications impose stricter limits. FLAC has a smaller limit of 24- bit in a METADATA_BLOCK_VORBIS_COMMENT , because it stores thumbnails and cover art in binary big-endian METADATA_BLOCK_PICTURE s outside of

658-578: Is considered to be a transmission protocol (Layer 1 in the OSI Reference Model ), it also performs some switching functions, as stated in the third bullet point requirement listed above. The most common SDH Networking functions are these: SDH network functions are connected using high-speed optic fibre. Optic fibre uses light pulses to transmit data and is therefore extremely fast. Modern optic fibre transmission makes use of wavelength-division multiplexing (WDM) where signals transmitted across

705-537: Is named after another Terry Pratchett character from the book Small Gods . The "Ogg" bitstream format , designed principally by the Xiph.Org Foundation, has been developed as the framework of a larger initiative aimed at producing a set of components for the coding and decoding of multimedia files, which are available free of charge and freely re-implementable in software and hardware. The format consists of chunks of data each called an " Ogg page ". Each page begins with

752-472: Is transmitted during time slot 1, sub-channel 2 during time slot 2, etc. One TDM frame consists of one time slot per sub-channel, and usually a synchronization channel and sometimes an error correction channel. After all of these the cycle starts again with a new frame, starting with the second sample, byte or data block from sub-channel 1, etc. TDM can be further extended into the time-division multiple access (TDMA) scheme, where several stations connected to

799-595: The Grand Theft Auto engines, as well as the audio files of the Java -based game, Minecraft . The more popular Vorbis codec had built-in support on many software players, and extensions were available for nearly all the rest. On May 16, 2007, the Free Software Foundation started a campaign to increase the use of Vorbis "as an ethically, legally and technically superior audio alternative to

846-719: The British Army used the Wireless Set No. 10 to multiplex 10 telephone conversations over a microwave relay as far as 50 miles. This allowed commanders in the field to keep in contact with the staff in England across the English Channel . In 1953, a 24-channel time-division multiplexer was placed in commercial operation by RCA Communications to send audio information between RCA's facility on Broad Street, New York, their transmitting station at Rocky Point and

893-533: The Matroska container format reached maturity and provided an alternative for people interested in combining Vorbis audio and arbitrary video codecs. As a result, OGM is no longer supported or developed and is formally discouraged by Xiph.org. Today, video in Ogg is found with the .ogv file extension, which is formally specified and officially supported. Software and codecs that support .ogm files are available without charge. Although Ogg had not reached anywhere near

940-565: The Ogg file format (with Vorbis , FLAC , Theora , Speex and Opus codecs ). It allows information such as the title, artist, album, track number or other information about the file to be added to the file itself. However, as the official Ogg Vorbis documentation notes, “[the comment header] is meant for short, text comments, not arbitrary metadata; arbitrary metadata belongs in a separate logical bitstream (usually an XML stream type) that provides greater structure and machine parseability.” Instead,

987-469: The .ogg filename extension was used for all files whose content used the Ogg container format. Since 2007, the Xiph.Org Foundation recommends that .ogg only be used for Ogg Vorbis audio files. The Xiph.Org Foundation decided to create a new set of file extensions and media types to describe different types of content such as .oga for audio only files, .ogv for video with or without sound (including Theora), and .ogx for multiplexed Ogg. As of November 7, 2017,

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1034-537: The FLAC tags in a little-endian METADATA_BLOCK_VORBIS_COMMENT . Other existing and proposed mechanisms are: The Ogg project began with a simple audio compression package as part of a larger project in 1993. The software was originally named Squish but due to an existing trade mark it was renamed to OggSquish . This name was later used for the whole Ogg project. In 1997, the Xiphophorus OggSquish

1081-566: The FLAC tags. The data is encoded in UTF-8 , and so any conforming Unicode string may be used as a value. Any field name is allowed, and there is no format that the data values must be in. This is in contrast to the ID3 format used for MP3s , which is highly structured. Field names are also permitted to be used more than once. It is encouraged to use this feature to support multiple values, for example two ARTIST=... fields to list both artists of

1128-591: The Ogg container format. Ogg is derived from "ogging", jargon from the computer game Netrek , which came to mean doing something forcefully, possibly without consideration of the drain on future resources. At its inception, the Ogg project was thought by the authors to be somewhat ambitious given the limited power of the PC hardware of the time. Although the name "Ogg" is unrelated to the character " Nanny Ogg " in Terry Pratchett 's Discworld novels, "Vorbis"

1175-481: The TDM frame is called a channel. In European systems, standard TDM frames contain 30 digital voice channels (E1), and in American systems (T1), they contain 24 channels. Both standards also contain extra bits (or bit time slots) for signaling and synchronization bits. Multiplexing more than 24 or 30 digital voice channels is called higher order multiplexing . Higher order multiplexing is accomplished by multiplexing

1222-400: The bitstreams to be decoded in sequence. A BSD-licensed library, called "libvorbis", is available to encode and decode data from "Vorbis" streams. Independent Ogg implementations are used in several projects such as RealPlayer and a set of DirectShow filters. Mogg, the "Multi-Track-Single-Logical-Stream Ogg-Vorbis", is the multi-channel or multi-track Ogg file format. The following is

1269-417: The characters "OggS" to identify the file as Ogg format. A "serial number" and "page number" in the page header identifies each page as part of a series of pages making up a bitstream . Multiple bitstreams may be multiplexed in the file where pages from each bitstream are ordered by the seek time of the contained data. Bitstreams may also be appended to existing files, a process known as "chaining", to cause

1316-527: The complementary equipment on the receiving end of the trunk line. Time-division multiplexing is used primarily for digital signals but may be applied in analog multiplexing , as above, in which two or more signals or bit streams are transferred appearing simultaneously as sub-channels in one communication channel, but are physically taking turns on the channel. The time domain is divided into several recurrent time slots of fixed length, one for each sub-channel. A sample byte or data block of sub-channel 1

1363-689: The current version of the Xiph.Org Foundation's reference implementation is libogg 1.3.3. Another version, libogg2, has been in development, but is awaiting a rewrite as of 2018. Both software libraries are free software , released under the New BSD License . Ogg reference implementation was separated from Vorbis on September 2, 2000. Ogg's various codecs have been incorporated into a number of different free and proprietary media players , both commercial and non-commercial, as well as portable media players and GPS receivers from different manufacturers. The Ogg Vorbis project started in 1993. It

1410-527: The fibre are transmitted at different wavelengths, creating additional channels for transmission. This increases the speed and capacity of the link, which in turn reduces both unit and total costs. Statistical time-division multiplexing (STDM) is an advanced version of TDM in which both the address of the terminal and the data itself are transmitted together for better routing. Using STDM allows bandwidth to be split over one line. Many college and corporate campuses use this type of TDM to distribute bandwidth. On

1457-422: The field layout of an Ogg page header: The segments provide a way to group segments into packets, which are meaningful units of data for the decoder. When the segment's length is indicated to be 255, this indicates that the following segment is to be concatenated to this one and is part of the same packet. When the segment's length is 0–254, this indicates that this segment is the final segment in this packet. Where

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1504-410: The intended function of Vorbis comments is to approximate the kind of information that might be hand-inked onto a blank faced CD-R or CD-RW : a few lines of notes briefly detailing the content. A Vorbis tag is a list of fields in the format FieldName=Data . The field name can be composed of printable ASCII characters, 0x20 ( space ) through 0x7D (‘}’), with 0x3D (‘=’) and 0x7E (‘~’) excluded. It

1551-562: The lack of formal video support in Ogg resulted in the development of the OGM file format, a hack on Ogg that allowed embedding of video from the Microsoft DirectShow framework into an Ogg-based wrapper. OGM was initially supported only by closed source Windows-only tools, but the codebase was subsequently opened. Later, video (and subtitle) support were formally specified for Ogg but in a manner incompatible with OGM. Independently,

1598-536: The line allowed the single line to carry short portions, each 1 ⁄ 8000 of a second, of up to 24 voice calls, in turn. The discrete signals on the trunk line carried 1.544 Mbit/s divided into 8000 separate frames per second, each composed of 24 contiguous octets and one framing bit. Each octet in a frame carried a single telephone call in turn. Thus each of 24 voice calls was encoded into two constant-bit-rate streams of 64 kbit/s (one in each direction), and converted back to conventional analog signals by

1645-410: The primary transmission protocol in most PSTN networks. It was developed to allow streams 1.544 Mbit/s and above to be multiplexed, in order to create larger SDH frames known as Synchronous Transport Modules (STM). The STM-1 frame consists of smaller streams that are multiplexed to create a 155.52 Mbit/s frame. SDH can also multiplex packet based frames e.g. Ethernet , PPP and ATM. While SDH

1692-569: The proprietary MP3 format". People were also encouraged to support the campaign by adding a web button to their website or blog . For those who did not want to download and use the FSF's suggested Ogg player ( VLC ), the Xiph.Org Foundation had an official codec for QuickTime -based applications in Windows and Mac OS X , such as iTunes players and iMovie applications; and Windows users could install

1739-442: The receiving station at Riverhead, Long Island, New York. The communication was by a microwave system throughout Long Island. The experimental TDM system was developed by RCA Laboratories between 1950 and 1953. In 1962, engineers from Bell Labs developed the first D1 channel banks, which combined 24 digitized voice calls over a four-wire copper trunk line between Bell central office analogue switches. A channel bank at each end of

1786-450: The same physical medium, for example sharing the same frequency channel, can communicate. Application examples include: In circuit-switched networks, such as the public switched telephone network (PSTN), it is desirable to transmit multiple subscriber calls over the same transmission medium to effectively utilize the bandwidth of the medium. TDM allows transmitting and receiving telephone switches to create channels ( tributaries ) within

1833-501: The specifications of Ogg encapsulations for other Xiph.Org codecs including Theora , Speex , FLAC and Opus . VorbisComment is the simplest and most widely supported mechanism for storing metadata with Xiph.Org codecs. Notably, one or more METADATA_BLOCK_PICTURE= ... in a VorbisComment for thumbnails and cover art have Base64 -encoded values of the corresponding FLAC METADATA_BLOCK_PICTURE . In other words, FLAC stores thumbnails and cover art in binary blocks—outside of

1880-434: The standard TDM frames. For example, a European 120 channel TDM frame is formed by multiplexing four standard 30 channel TDM frames. At each higher order multiplex, four TDM frames from the immediate lower order are combined, creating multiplexes with a bandwidth of n *64 kbit/s, where n = 120, 480, 1920, etc. There are three types of synchronous TDM: T1, SONET/SDH, and ISDN. Plesiochronous digital hierarchy (PDH)

1927-684: The ubiquity of the MPEG standards (e.g., MP3 / MP4 ), as of 2006, it was commonly used to encode free content (such as free music, multimedia on Wikimedia Foundation projects and Creative Commons files) and had started to be supported by a significant minority of digital audio players . Also supporting the Ogg format were many popular video game engines, including Doom 3 , Unreal Tournament 2004 , Halo: Combat Evolved , Jets'n'Guns , Mafia: The City of Lost Heaven , Myst IV: Revelation , StepMania , Serious Sam: The Second Encounter , Lineage 2 , Vendetta Online , Battlefield 2 , and

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1974-557: Was described as "an attempt both to create a flexible compressed audio format for modern audio applications as well as to provide the first audio format that is common on any and every modern computer platform". The OggSquish was in 2000 referred to as "a group of several related multimedia and signal processing projects". In 2000, two projects were in active development for planned release: Ogg Vorbis format and libvorbis—the reference implementation of Vorbis. Research also included work on future video and lossless audio coding. In 2001, OggSquish

2021-510: Was developed as a standard for multiplexing higher order frames. PDH created larger numbers of channels by multiplexing the standard Europeans 30 channel TDM frames. This solution worked for a while; however PDH suffered from several inherent drawbacks which ultimately resulted in the development of the Synchronous Digital Hierarchy (SDH). The requirements which drove the development of SDH were these: SDH has become

2068-468: 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. Time-division multiplexing was first developed for applications in telegraphy to route multiple transmissions simultaneously over a single transmission line. In the 1870s, Émile Baudot developed a time-multiplexing system of multiple Hughes telegraph machines. In 1944,

2115-412: Was originally named "Squish" but that name was already trademarked, so the project underwent a name change. The new name, "OggSquish", was used until 2001 when it was changed again to "Ogg". Ogg has since come to refer to the container format , which is now part of the larger Xiph.org multimedia project. Today, "Squish" (now known as "Vorbis") refers to a particular audio coding format typically used with

2162-454: Was renamed to Ogg and it was described as "the umbrella for a group of several related multimedia and signal processing projects". Ogg has come to stand for the file format , as part of the larger Xiph.org multimedia project. Squish became just the name of one of the Ogg codecs. In 2009, Ogg is described as "a multimedia container format, and the native file and stream format for the Xiph.org multimedia codecs". The Ogg reference implementation

2209-627: Was separated from Vorbis on September 2, 2000. In May 2003, two Internet RFCs were published relating to the format. The Ogg bitstream was defined in RFC ; 3533 (which is classified as 'informative') and its Internet content type ( application/ogg ) in RFC ; 3534 (which is, as of 2006, a proposed standard protocol). In September 2008, RFC 3534 was obsoleted by RFC  5334 , which added content types video/ogg , audio/ogg and filename extensions .ogx, .ogv, .oga, .spx. In 2002,

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