Information about Variable Bit Rate
Variable bitrate (VBR), or less commonly variable bit rate, 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 is calculated to produce an average bitrate for the file that will represent its overall sound quality.
MP3, WMA, Vorbis, and AAC audio files can optionally be encoded in VBR. Variable bit rate encoding is also commonly used on MPEG-2 video.
The disadvantages are that it may take more time to encode, as the process is more complex, and that some hardware might not be compatible with VBR files.
As of December 2006, most newly produced portable music devices and software offer modern support for VBR encoded files. Devices that support only CBR encoded files are becoming increasingly difficult to find.
In the past, many hardware and software players could not decode variable bitrate files properly, partly because the various VBR encoders used were not well developed . This resulted in common use of CBR over VBR for the sake of compatibility.
Support for VBR in AAC and MP3 files is found in most modern digital audio players, including those released by Apple Inc., Creative Technology, and SanDisk. Early VBR algorithms occasionally introduced audible artifacts when encoding monotone or minimal tones (for example audiobooks and acoustic music). These artifacts often mimicked a "digital chirp" during the quiet portions of the song or when there was only speaking. As VBR encoding algorithms have improved, these problems have been resolved in subsequent generations of the VBR standard.
(See for formats and for codecs)
Debt, AIDS, Trade in Africa (or DATA) is a multinational non-government organization founded in January 2002 in London by U2's Bono along with Bobby Shriver and activists from the Jubilee 2000 Drop
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MP3, WMA, Vorbis, and AAC audio files can optionally be encoded in VBR. Variable bit rate encoding is also commonly used on MPEG-2 video.
Pros and cons
The advantages of VBR are that it produces a better quality-to-space ratio compared to a CBR file of the same size. The bits available are used more flexibly to encode the music more accurately, with fewer bits used in less demanding passages and more bits used in difficult-to-encode passages.The disadvantages are that it may take more time to encode, as the process is more complex, and that some hardware might not be compatible with VBR files.
As of December 2006, most newly produced portable music devices and software offer modern support for VBR encoded files. Devices that support only CBR encoded files are becoming increasingly difficult to find.
In the past, many hardware and software players could not decode variable bitrate files properly, partly because the various VBR encoders used were not well developed . This resulted in common use of CBR over VBR for the sake of compatibility.
Support for VBR in AAC and MP3 files is found in most modern digital audio players, including those released by Apple Inc., Creative Technology, and SanDisk. Early VBR algorithms occasionally introduced audible artifacts when encoding monotone or minimal tones (for example audiobooks and acoustic music). These artifacts often mimicked a "digital chirp" during the quiet portions of the song or when there was only speaking. As VBR encoding algorithms have improved, these problems have been resolved in subsequent generations of the VBR standard.
See also
| Lossless compression methods | ||||
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| Audio compression methods |
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| Image compression methods |
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| Video compression |
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| Timeline of information theory, data compression, and error-correcting codes | ||||
Telecommunication is the transmission of signals over a distance for the purpose of communication. In modern times, this process typically involves the sending of electromagnetic waves by electronic transmitters, but in earlier times telecommunication may have involved the use of
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computing is synonymous with counting and calculating. Originally, people that performed these functions were known as computers. Today it refers to a science and technology that deals with the computation and the manipulation of symbols.
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bitrate (sometimes written bit rate, data rate or as a variable R or fb) is the number of bits that are conveyed or processed per unit of time. Bit rate is synonymous to data rate and digital bandwidth.
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Constant bitrate (CBR) is a term used in telecommunications, relating to the quality of service. Compare with variable bit rate.
When referring to codecs, constant bit rate encoding means that the rate at which a codec's output data should be consumed is constant.
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When referring to codecs, constant bit rate encoding means that the rate at which a codec's output data should be consumed is constant.
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- For other uses, see Data (disambiguation).
Debt, AIDS, Trade in Africa (or DATA) is a multinational non-government organization founded in January 2002 in London by U2's Bono along with Bobby Shriver and activists from the Jubilee 2000 Drop
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Average bitrate refers to the average amount of data transferred per second. This is commonly referred to for digital music or video. An MP3 file, for example, that has an average bit rate of 128 kbit/s transfers, on average, 128,000 bits every second.
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Sound quality generally is the quality of the audio output from various electronic devices.
Sound quality can be defined as the degree of accuracy with which a device records or emits the original sound waves.
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Sound quality can be defined as the degree of accuracy with which a device records or emits the original sound waves.
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MPEG-1 Audio Layer 3
File extension:
MIME type:
Type of format: Audio MPEG-1 Audio Layer 3, more commonly referred to as MP3, is an audio encoding format.
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File extension:
.mp3MIME type:
audio/mpegType of format: Audio MPEG-1 Audio Layer 3, more commonly referred to as MP3, is an audio encoding format.
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Windows Media Audio
File extension:
MIME type:
Uniform Type Identifier: com.microsoft.windows-?media-wma
Developed by: Microsoft
Type of format: audio file format Windows Media Audio (WMA
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File extension:
.wmaMIME type:
audio/x-ms-wmaUniform Type Identifier: com.microsoft.windows-?media-wma
Developed by: Microsoft
Type of format: audio file format Windows Media Audio (WMA
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Vorbis
File extension:
MIME type:
Developed by: Xiph.Org Foundation
Type of format: Audio codec
Contained by: Ogg
Standard(s): Specification
Vorbis
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File extension:
.ogg .oga [1]MIME type:
audio/oggDeveloped by: Xiph.Org Foundation
Type of format: Audio codec
Contained by: Ogg
Standard(s): Specification
Vorbis
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Advanced Audio Coding
File extension:
Type of format: Lossy compression
Container for: Audio
Advanced Audio Coding (AAC) is a standardized, lossy compression and encoding scheme for
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File extension:
.m4a, .m4b, .m4p, .m4v, .aac, .3gp, .mp4Type of format: Lossy compression
Container for: Audio
Advanced Audio Coding (AAC) is a standardized, lossy compression and encoding scheme for
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MPEG-2 is a standard for "the generic coding of moving pictures and associated audio information".[1] It describes a combination of lossy video compression and lossy audio compression (audio data compression) methods which permit storage and transmission of movies using
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Hardware is a general term that refers to the physical artifacts of a technology.It may also mean the physical components of a computer system.
Hardware historically meant the metal parts and fittings that were used to make wooden products stronger, more functional, longer
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Hardware historically meant the metal parts and fittings that were used to make wooden products stronger, more functional, longer
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Media Player was a media player originally included in Windows 3.0 with Multimedia Extensions and a slightly updated version was included with Windows 3.1x. Media Player received a facelift with Video for Windows, with an OLE2 version provided with the runtime software.
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MP3 player, a digital audio player or "DAP" is a portable, handheld digital music player that stores, organizes and plays MP3 and often other audio files. Most DAPs are powered by rechargeable batteries, some of which are not user replaceable.
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Apple Inc.
Public (NASDAQ: AAPL , LSE: ACP , FWB: APC )
Founded California (April 1 1976, as Apple Computer, Inc.)
Headquarters 1 Infinite Loop, Cupertino, California
Key people Steve Jobs, CEO & Co-founder
Steve Wozniak, Co-founder
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Public (NASDAQ: AAPL , LSE: ACP , FWB: APC )
Founded California (April 1 1976, as Apple Computer, Inc.)
Headquarters 1 Infinite Loop, Cupertino, California
Key people Steve Jobs, CEO & Co-founder
Steve Wozniak, Co-founder
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Creative Technology Limited
Public
SGX: C76 , NASDAQ: CREAF
Founded July 1 1981
Headquarters Singapore
Key people Sim Wong Hoo, Founder & CEO
Products Multimedia, IT, MP3 players
Revenue US$1.2 billion (2005)
Net income US$0.
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Public
SGX: C76 , NASDAQ: CREAF
Founded July 1 1981
Headquarters Singapore
Key people Sim Wong Hoo, Founder & CEO
Products Multimedia, IT, MP3 players
Revenue US$1.2 billion (2005)
Net income US$0.
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SanDisk Corporation (NASDAQ: SNDK ), formerly SunDisk, is an American multinational corporation which designs and markets flash memory card products. SanDisk was founded in 1988 by Eli Harari and Sanjay Mehrotra, a non-volatile memory technology expert.
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Constant bitrate (CBR) is a term used in telecommunications, relating to the quality of service. Compare with variable bit rate.
When referring to codecs, constant bit rate encoding means that the rate at which a codec's output data should be consumed is constant.
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When referring to codecs, constant bit rate encoding means that the rate at which a codec's output data should be consumed is constant.
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data compression or source coding is the process of encoding information using fewer bits (or other information-bearing units) than an un-encoded representation would use through use of specific encoding schemes.
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Lossless data compression is a class of data compression algorithms that allows the exact original data to be reconstructed from the compressed data. This can be contrasted to lossy data compression, which does not allow the exact original data to be reconstructed from the
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Information theory is a branch of applied mathematics and engineering involving the quantification of information to find fundamental limits on compressing and reliably communicating data.
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Shannon entropy or information entropy is a measure of the uncertainty associated with a random variable.
Shannon entropy quantifies the information contained in a piece of data: it is the minimum average message length, in bits (if using base-2 logarithms), that must
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Shannon entropy quantifies the information contained in a piece of data: it is the minimum average message length, in bits (if using base-2 logarithms), that must
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In computer science, the Kolmogorov complexity (also known as descriptive complexity, Kolmogorov-Chaitin complexity, stochastic complexity, algorithmic entropy, or program-size complexity
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Redundancy in information theory is the number of bits used to transmit a message minus the number of bits of actual information in the message. Informally, it is the amount of wasted "space" used to transmit certain data.
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In information theory an entropy encoding is a lossless data compression scheme that is independent of the media’s specific characteristics.
One of the main types of entropy coding assigns codes to symbols so as to match code lengths with the probabilities of the
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One of the main types of entropy coding assigns codes to symbols so as to match code lengths with the probabilities of the
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Huffman coding is an entropy encoding algorithm used for lossless data compression. The term refers to the use of a variable-length code table for encoding a source symbol (such as a character in a file) where the variable-length code table has been derived in a particular way
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Adaptive Huffman coding (also called Dynamic Huffman coding) is an adaptive coding technique based on Huffman coding, building the code as the symbols are being transmitted, having no initial knowledge of source distribution, that allows one-pass encoding and adaptation to
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Arithmetic coding is a method for lossless data compression. Normally, a string of characters such as the words "hello there" is represented using a fixed number of bits per character, as in the ASCII code.
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