network protocols handbook.pdf

139Protocols GuideVoice Over IP(VOIP) - Media / CODECMedia / CODECProtocol NameG.7xx: Audio (Voice) CompressionProtocolsProtocol DescriptionG.7xx is a suite of ITU-T standards for audio compression andde-commpressions. It is primarily used in telephony. In telephony,there are 2 main algorithms defined in the standard, mu-lawalgorithm (used in America) and a-law algorithm (used in Europeand the rest of the world). Both are logarithmic, but the latera-law was specifically designed to be simpler for a computer toprocess. The G.7xx protocol suite is composed of the followingprotocols:G.711 Pulse code modulation (PCM) of voice frequencieson a 64 kbps channel.G.721 32 kbit/s adaptive differential pulse code modulation(ADPCM)G.722 7 kHz audio-coding within 64 kbit/sG.722.1 Coding at 24 and 32 kbit/s for hands-free operationin systems with low frame lossG.722.2 Wideband coding of speech at around 16 kbit/susing adaptive multi-rate wideband (AMR-WB)G.726 40, 32, 24, 16 kbit/s adaptive differential pulsecode modulation (ADPCM)G.727 5-, 4-, 3- and 2-bit/sample embedded adaptivedifferential pulse code modulation (ADPCM)G.728 Coding of speech at 16 kbit/s using low-delaycode excited linear predictionG.729 Coding of speech at 8 kbit/s using conjugatestructurealgebraic-code-excited linear-prediction(CS-ACELP)Protocol StructureName(ADPCM)DVIstandardizedbyIntel,IMAdescriptionbit rate(kb/s)samplingrate(kHz)framesize(ms)ADPCM 32 8 sampleremarksG.711 ITU-T Pulse code modulation (PCM) 64 8 sample mu-law (US, Japan) and A-law (Europe) compandingG.721 ITU-TAdaptive differential pulse code modulation(ADPCM)G.722 ITU-T 7 kHz audio-coding within 64 kbit/s 64 16 sampleG.722.1ITU-TG.723 ITU-TG.723.1ITU-TG.726 ITU-TG.727 ITU-TG.728 ITU-TG.729 ITU-TGSM06.10ETSICoding at 24 and 32 kbit/s for hands-freeoperation in systems with low frame lossExtensions of Recommendation G.721adaptive differential pulse code modulationto 24 and 40 kbit/s for digital circuit multiplicationequipment applicationDual rate speech coder for multimediacommunications transmitting at 5.3 and6.3 kbit/s40, 32, 24, 16 kbit/s adaptive differentialpulse code modulation (ADPCM)5-, 4-, 3- and 2-bit/sample embeddedadaptive differential pulse code modulation(ADPCM)Coding of speech at 16 kbit/s using lowdelaycode excited linear predictionCoding of speech at 8 kbit/s using conjugate-structurealgebraic-code-excitedlinear-prediction (CS-ACELP)Regular Pulse Excitation Long Term Predictor(RPE-LTP)32 8 sample Now described in G.726; obsolete.24/32 16 2024/40 8 sample5.6/6.3 8 3016 / 24 /32 / 40Subband-codec that divides 16 kHz band into two subbands,each coded using ADPCMSuperceded by G.726; obsolete. This is a completely differentcodec than G.723.1.Part of H.324 video conferencing. It encodes speech or otheraudio signals in frames using linear predictive analysis-bysynthesiscoding. The excitation signal for the high rate coderis Multipulse Maximum Likelihood Quantization (MP-MLQ) andfor the low rate coder is Algebraic-Code-Excited Linear-Prediction(ACELP).8 sample ADPCM; replaces G.721 and G.723.var. ? sample ADPCM. Related to G.726.16 8 CELP. Annex J offers variable-bit rate operation for DCME.8 8 10 Low delay (15 ms)13 8 22.5 Used for GSM cellular telephony.