Phone Call Recorder

mu-law

µ-law (mu-law). G.711 An alternative to A-law PCM , used for the B-channel of T1 streams. In telecommunication, a mu-law algorithm (?-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. It is similar to the A-law algorithm used in Europe. This encoding is used because speech has a wide dynamic range that does not lend itself well to efficient linear digital encoding. Moreover, perceived intensity (loudness) is logarithmic. Mu-law encoding effectively reduces the dynamic range of the signal, thereby increasing the coding efficiency and resulting in a signal-to-distortion ratio that is greater than that obtained by linear encoding for a given number of bits. The mu-law algorithm is also used in some rather standard programming language approaches for storing and creating sound (such as the classes in the sun.audio Java package in Java 1.1, in the .au format, and in some C# methods). A special feature of mu-law encoding is that zero is actually the range of values near zero sound pressure. This means that near silence is encoded as zero, without introducing quantization noise as the value flips between positive and negative values. The inventors at Bell Labs arranged this so that long-distance telephony would have less noise, and therefore be perceived as higher quality. This also reduces the size of run-length encoded speech samples. These are both significant advantages over its main competitor, A-law encoding. The A-law algorithm provides a slightly larger dynamic range than the mu-law at the cost of worse proportional distortion for small signals. By convention, A-law is used for an international connection if at least one country uses it.

List of telephony terms:

3gpp - a-law - abbreviated dialing - adsl - ani - answering machine - apn - automatic ring back - b-channel - baud - bell 202 modem - bit rate - bonding - bri - busy signal - cable modem - call-progress tones - call accounting - call capture - call forwarding - call originator - call park - call pick-up - call transfer - call waiting - call waiting deluxe - called party - caller id - caller id spoofing - calling party - carrier wave - cbr - ccitt - cdma - cdma2000 - cellular repeater - celp - channel - clec - clock rate - codec - collect call - conference - conference call - crc - csd - d-channel - data compression - device driver - dial-up - dial - dial tone - direct-inward-dialing - direct distance dialing - distinctive ring - dnis - dsl - dsp - dtmf - dtr - duplex - echo cancellation - edge - extension - fax - fcc - fdma - fidonet - follow-me - g.711 - g.723.1 - g.723 - g.726 - g.lite - gprs - gps - gsm - h.323 - harmonic - headphones - hscsd - hspda - iad - idsn - internet call waiting - isp - ivr - jack plug - local loop - long distance - microcontroller - mobile phone - modem - modulation - mu-law - music-on-hold - night service - off-hook - on-hook - pabx - pager - payphone - pbx - pcm - pots - prank call - precise tone plan - pstn - pulse dialling - push to talk - ring modulation - ring tone - ringback - ringing signal - rj11 - roaming - serial communications - serial port - signal noise - sim - simplex - sit - sms - softmodem - switchboard operator - tapi - tdma - telecommunications - telemarketing - telephone - telephone call - telephone card - telephone company - telephone exchange - telephone line - telephone number - telephone numbering plan - telephone operator - telephone switchboard - telephony - tts - twisted pair - umts - v.32 - v.32bis - v.34 - v.42bis - vbr - vertical service code - voicemail - voip - vox - wap - wav - wi-fi - wimax - wire