NationMaster - Encyclopedia: G.711

G.711 is an ITU-T standard for audio companding. It is primarily used in telephony. The standard was released for usage in 1972. The ITU Telecommunication Standardization Sector (ITU-T) coordinates standards for telecommunications on behalf of the International Telecommunication Union (ITU) and is based in Geneva, Switzerland. ... A waveform before and after the compression stage of non-linear companding In telecommunication, signal processing, and thermodynamics, companding (occasionally called compansion) is a method of reducing the effects of a channel with limited dynamic range. ... In telecommunication, Telephony encompasses the general use of equipment to provide voice communication over distances. ... Year 1972 (MCMLXXII) was a leap year starting on Saturday (link will display full calendar) of the Gregorian calendar. ...

G.711 represents logarithmic pulse-code modulation (PCM) samples for signals of voice frequencies, sampled at the rate of 8000 samples/second. PCM redirects here. ...

Types

There are two main algorithms defined in the standard, the µ-law algorithm (used in North America & Japan) and A-law algorithm (used in Europe and the rest of the world). Both are logarithmic, but A-law was specifically designed to be simpler for a computer to process. The standard also defines a sequence of repeating code values which defines the power level of 0 dB. In telecommunication, a mu-law algorithm (Î¼-law) is a standard analog signal compression or companding algorithm, used in digital communications systems of the North American and Japanese digital hierarchies, to optimize (in other words, modify) the dynamic range of an audio analog signal prior to digitizing. ... Graph of Î¼-law & A-law algorithms An a-law algorithm is a standard companding algorithm, used in European digital communications systems to optimize, modify, the dynamic range of an analog signal for digitizing. ... A logarithmic scale is a scale of measurement that uses the logarithm of a physical quantity instead of the quantity itself. ... For other uses, see Decibel (disambiguation). ...

The µ-law and A-law algorithms encode 14-bit and 13-bit signed linear PCM samples (respectively) to logarithmic 8-bit samples. Thus, the G.711 encoder will create a 64 kbit/s bitstream for a signal sampled at 8 kHz. An encoder is a device used to encode a signal (such as a bitstream) or data into a form that is acceptable for transmission or storage. ...

G.711 A-Law

A-law encoding thus takes a 13-bit signed linear audio sample as input and converts it to an 8 bit value as follows:

Where s is the sign bit. So for example, 1000000010101111 maps to 10001010 (according to the first row of the table), and 0000000110101111 maps to 00011010 (according to the second).

This can be seen as a floating point number with 4 bits of mantissa and 3 bits of exponent. A floating-point number is a digital representation for a number in a certain subset of the rational numbers, and is often used to approximate an arbitrary real number on a computer. ... For the traditional use of the word mantissa in mathematics, see common logarithm. ... In mathematics, exponentiation is a process generalized from repeated multiplication, in much the same way that multiplication is a process generalized from repeated addition. ...

In addition, the standard specifies that all resulting even bits are inverted before the octet is transmitted. This is to provide plenty of 0/1 transitions to facilitate the clock recovery process in the PCM receivers. Thus, a silent A-law encoded PCM channel has the 8 bit samples coded 0x55 instead of 0x00 in the octets (or 0xD5 if the sign bit happens to be set), and a silent μ-law encoded PCM has 0xFF in the 8 bit samples. Some digital data streams, especially high-speed serial data streams (such as the raw stream of data from the magnetic head of a disk drive) are sent without an accompanying clock. ...

Note that the ITU define bit 0 to have the value 128 and bit 7 to have the value 1. (This is different from the more widely accepted convention where bit 7 = 128 and bit 0 = 1.)

Note that when data is sent over E0 (G.703), MSB (signbit) is sent first and LSB is sent last. G.703 is a ITU-T standard for transmitting voice or data over digital carriers such as T1 and E1. ...

Features

Alameda Packet loss concealment (PLC) is a technique to mask the effects of packet loss in VoIP communications. ... Discontinuous transmission (DTX) is a method of momentarily powering-down, or muting, a mobile or portable wireless telephone set when there is no voice input to the set. ... Voice activity detection or voice activity detector is an algorithm used in speech processing wherein, the presence or absence of human speech is detected from the audio samples. ... Comfort noise is artifical background noise used in radio and wireless communications to fill the silent time in a transmission resulting from voice activity detection. ... PSQM is an acronym for Percentual Speech Quality Measurement defined in ITU standard P.861 ... [info from searchnetworking. ... PSQM is an acronym for Percentual Speech Quality Measurement defined in ITU standard P.861 ... [info from searchnetworking. ...

References

See also

G.722[1] is a ITU-T standard wideband speech codec operating at 48-64 kbit/s. ... G.722. ... Adaptive Multi Rate - WideBand or AMR-WB is a speech coding standard developed after the AMR using same technology like ACELP. The codec provides excellent speech quality due to wider speech bandwidth of 50 - 7000 Hz compared to narrowband speech codecs which in general are optimized for POTS wireline quality... This article is in need of attention from an expert on the subject. ... G.723. ... G.726 is ITU-T speech codec operating at bit rates of 16-40 kbit/s. ... G.728 is a ITU-T standard for speech coding operating at 16 kbit/s. ... G.729 is an audio data compression algorithm for voice that compresses voice audio in chunks of 10 milliseconds. ... G.729 is an audio data compression algorithm for voice that compresses voice audio in chunks of 10 milliseconds. ... The following is a list of codecs. ...

External links

Categories: Audio codecs | Speech codecs | ITU-T recommendations [info from searchnetworking. ... Look up Multimedia in Wiktionary, the free dictionary. ... Source coding redirects here. ... Video compression refers to making a digital video signal use less data, without noticeably reducing the quality of the picture. ... â€œISOâ€ redirects here. ... The International Electrotechnical Commission (IEC) is an international standards organization dealing with electrical, electronic and related technologies. ... Motion JPEG, also known as M-JPEG, is a video file format consisting of a sequence of individual JPEG images; unlike other video compression algorithms, each frame is an image unto itself. ... MPEG-1 defines a group of Audio and Video (AV) coding and compression standards agreed upon by MPEG (Moving Picture Experts Group). ... MPEG-2 is a standard for the generic coding of moving pictures and associated audio information [1]. It is widely used around the world to specify the format of the digital television signals that are broadcast by terrestrial (over-the-air), cable, and direct broadcast satellite TV systems. ... MPEG-4 Part 2 is a video compression technology developed by MPEG. It belongs to the MPEG-4 ISO/IEC standard (ISO/IEC 14496-2). ... H.264 is a standard for video compression. ... The ITU Telecommunication Standardization Sector (ITU-T) coordinates standards for telecommunications on behalf of the International Telecommunication Union (ITU) and is based in Geneva, Switzerland. ... H.261 is an 1990 ITU video coding standard originally designed for transmission over ISDN lines on which data rates are multiples of 64 kbit/s. ... H.262 is an ITU-T digital video coding standard. ... H.263 is a video codec designed by the ITU-T as a low-bitrate encoding solution for videoconferencing. ... H.264 is a standard for video compression. ... Audio Video Standard, or AVS, is a compression codec for digital audio and video, and a possible alternative to H.264/AAC/Vorbis [1], meant to potentially replace MPEG-2. ... Bink is a video file format (extension . ... Dirac is a prototype algorithm for the encoding and decoding (see codec) of raw video. ... Indeo Video (commonly known now simply as Indeo) is a video codec developed by Intel in 1992. ... Motion JPEG (M-JPEG) is an informal name for multimedia formats where each video frame or interlaced field of a digital video sequence is separately compressed as a JPEG image. ... Pixlet is a video codec created by Apple Computer and based on wavelets, designed to enable viewing of full resolution, high resolution movies in real time at low DV data rates. ... RealVideo is a proprietary video format developed by RealNetworks. ... RTVideo RTVideo is Microsofts default video codec for OCS. RTVideo is a proprietrary codec. ... Smacker video is a video file format (with the file extension) developed by RAD Game Tools and oftenly used in computer games. ... Theora is a video codec being developed by the Xiph. ... VC-1 is the informal name of the SMPTE 421M video codec standard initially developed by Microsoft. ... TrueMotion VP6 is a video codec developed by On2 Technologies as a successor to earlier efforts such as VP3 and VP5. ... TrueMotion VP7 is a video codec developed by On2 Technologies as a successor to earlier efforts such as VP3, VP5 and TrueMotion VP6. ... Windows Media Video (WMV) is a generic name for the set of video codec technologies developed by Microsoft. ... This article is about a process which reduces the data rate or file size of digital audio signals. ... â€œISOâ€ redirects here. ... The International Electrotechnical Commission (IEC) is an international standards organization dealing with electrical, electronic and related technologies. ... For other uses, see MP3 (disambiguation). ... MPEG-1 Audio Layer II (MP2, sometimes Musicam) is an audio codec defined by ISO/IEC 11172-3. ... MPEG-1 Audio Layer I, commonly abbreviated to MP1, is one of three audio codecs included in the MPEG-1 standard. ... MPEG-4 AAC DRM encoding as used in the iTunes Store Advanced Audio Coding (AAC) is a standardized, lossy compression and encoding scheme for digital audio. ... High Efficiency AAC (HE-AAC) is a lossy data compression scheme for digital audio. ... High Efficiency AAC (HE-AAC) is a lossy data compression scheme for digital audio. ... The ITU Telecommunication Standardization Sector (ITU-T) coordinates standards for telecommunications on behalf of the International Telecommunication Union (ITU) and is based in Geneva, Switzerland. ... G.722[1] is a ITU-T standard wideband speech codec operating at 48-64 kbit/s. ... G.722. ... Adaptive Multi Rate - WideBand or AMR-WB is a speech coding standard developed after the AMR using same technology like ACELP. The codec provides excellent speech quality due to wider speech bandwidth of 50 - 7000 Hz compared to narrowband speech codecs which in general are optimized for POTS wireline quality... This article is in need of attention from an expert on the subject. ... G.723. ... G.726 is ITU-T speech codec operating at bit rates of 16-40 kbit/s. ... G.728 is a ITU-T standard for speech coding operating at 16 kbit/s. ... G.729 is an audio data compression algorithm for voice that compresses voice audio in chunks of 10 milliseconds. ... The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ... G.729 is an audio data compression algorithm for voice that compresses voice audio in chunks of 10 milliseconds. ... Dolby Digital is the marketing name for a series of lossy audio compression technologies by Dolby Laboratories. ... Apple Lossless (also known as Apple Lossless Encoder, ALE, or Apple Lossless Audio Codec, ALAC) is an audio codec developed by Apple Inc. ... Adaptive Transform Acoustic Coding (ATRAC) is a family of proprietary audio compression algorithms developed by Sony. ... Free Lossless Audio Codec (FLAC) is a popular file format for audio data compression. ... internet Low Bit Rate Codec (iLBC) is a royalty free narrowband speech codec, developed by Global IP Sound (GIPS). ... Monkeyâ€™s Audio is a file format for audio data compression. ... In telecommunication, a mu-law algorithm (Î¼-law) is a standard analog signal compression or companding algorithm, used in digital communications systems of the North American and Japanese digital hierarchies, to optimize (in other words, modify) the dynamic range of an audio analog signal prior to digitizing. ... Musepack or MPC is an open source lossy audio codec, specifically optimized for transparent compression of stereo audio at bitrates of 160-180 kbit/s. ... Nellymoser is a single-channel (mono) format optimized for low-bitrate transmission of audio. ... Please wikify (format) this article as suggested in the Guide to layout and the Manual of Style. ... RealAudio is a proprietary audio format developed by RealNetworks. ... RTAudio is a Microsoft produced adaptive wide-band speech codec. ... SHN (Shorten) is a file format used to losslessly compress CD-quality audio files (44. ... Speex is a free software speech codec that may be used on VoIP applications and podcasts. ... Vorbis is an open source, lossy audio codec project headed by the Xiph. ... WavPack is a free, open source lossless audio compression format developed by David Bryant. ... Windows Media Audio (WMA) is an audio data compression technology developed by Microsoft. ... TAK (Toms lossless Audio Kompressor) is a lossless audio compressor which promises compression performance similar to Monkeys Audio â€œHighâ€ and decompression speed similar to FLAC. The codec also supports streaming (necessary headers for decompressing the audio are written to the stream every 2 seconds), error tolerance (single bit... Image compression is the application of Data compression on digital images. ... â€œISOâ€ redirects here. ... The International Electrotechnical Commission (IEC) is an international standards organization dealing with electrical, electronic and related technologies. ... The ITU Telecommunication Standardization Sector (ITU-T) coordinates standards for telecommunications on behalf of the International Telecommunication Union (ITU) and is based in Geneva, Switzerland. ... JPG redirects here. ... JPEG 2000 is a wavelet-based image compression standard. ... The Joint Photographic Experts Group, in addition to their well-known lossy image compression techniques, JPEG and JPEG 2000, also have three standards for lossless compression (of which JPEG-LS has a lossy mode): Lossless JPEG was developed as a late addition to JPEG in 1993, using a completely different... JBIG is a lossless image compression standard from the Joint Bi-level Image Experts Group, standardized as ISO/IEC standard 11544 and as ITU-T recommendation T.82. ... JBIG2 is an image compression standard for bi-level images, developed by the Joint Bi-level Image Experts Group. ... PNG (Portable Network Graphics), sometimes pronounced as ping, is a relatively new bitmap image format that is becoming popular on the World Wide Web and elsewhere. ... Wireless Application Protocol Bitmap Format (shortened to Wireless Bitmap and with file extension . ... .BMP or . ... GIF (Graphics Interchange Format) is a bitmap image format that is widely used on the World Wide Web, both for still images and for animations. ... ICER is a wavelet-based image compression file format used by the NASA Mars Rovers. ... ILBM is a subtype of the Interchange File Format used for storing picture data. ... PCX is an image file format that uses a simple form of run-length encoding (a type of lossless compression algorithm). ... PGF (Progressive Graphics File) is a wavelet-based bitmapped image format that employs lossless and lossy data compression. ... Truevisions (now Pinnacle Systems) TGA File Format, often referred to as TARGA File Format, is a raster graphics file format. ... â€œTIFFâ€ redirects here. ... JPEG XR (formerly HD Photo (formerly Windows Media Photo) ) is a still image compression algorithm and file format for continuous tone photographic images, developed by Microsoft as a part of the Windows Media family. ... A container format is a computer file format that can contain various types of data, compressed by means of standardized codecs. ... 3GP is a multimedia container format defined by the Third Generation Partnership Project (3GPP) for use on 3G mobile phones. ... Advanced Systems Format (formerly Advanced Streaming Format, Active Streaming Format) is Microsofts proprietary digital audio/digital video container format, especially meant for streaming media. ... // Audio-Video Interleaved, known by its acronym AVI, is a multimedia container format introduced by Microsoft in November 1992 as part of its Video for Windows technology. ... Bink is a video file format (extension . ... DivX is a video codec created by DivX, Inc. ... DPX is also the name given to a mounting medium, see Di-n-butylPhthalate in Xylene. ... Flash Video is the name of a file format used to deliver video over the Internet using Adobe Flash Player (formerly known as Macromedia Flash Player) version 6, 7, 8, or 9. ... // The Matroska Multimedia Container is an open standard free multimedia container format that can hold an unlimited number of video, audio, picture or subtitle tracks inside a single file. ... For other parts of the MPEG-4 standard, see MPEG-4. ... Material eXchange Format (MXF) is a container format for professional digital video and audio media defined by a set of SMPTE standards. ... NUT is a patent-free, multimedia container format originally conceived by a few MPlayer and FFmpeg developers that were dissatisfied with the limitations of all currently available multimedia container formats such as AVI or Matroska. ... Ogg is an open standard for a free container format for digital multimedia, unrestricted by software patents and designed for efficient streaming and manipulation. ... Ogg Media (OGM), meaning Ogg Media File, is a container format (for video, audio and subtitle streams). ... QuickTime is a multimedia framework developed by Apple Inc. ... RealMedia is a multimedia container format created by RealNetworks. ... Smacker video is a video file format (with the file extension) developed by RAD Game Tools and oftenly used in computer games. ... A VOB file (DVD-Video Object or Versioned Object Base) is a container format contained in DVD-Video media. ... Audio Interchange File Format (AIFF) is an audio file format standard used for storing sound data for personal computers and other electronic audio devices. ... The Au file format is a simple audio file format that consists of a header of 6 32-bit words and then the data (high-order byte comes first). ... WAV (or WAVE), short for Waveform audio format, is a Microsoft and IBM audio file format standard for storing audio on PCs. ...

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