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G.7xx: Audio (Voice) Compression Protocols (CODEC) (G.711, G.721, G.722, G.726, G.727, G.728, G.729)
G.7xx, including G.711, G.721, G.722, G.726, G.727, G.728, G.729, is a suite of ITU-T standards for audio compression and de-commpression. It is primarily used in telephony. In telephony, there are 2 main algorithms defined in the standard, mu-law algorithm (used in America) and a-law algorithm (used in Europe and the rest of the world). Both are logarithmic, but the later a-law was specifically designed to be simpler for a computer to process. The G.7xx protocol suite compose the following protocols:
G.711 - Pulse code modulation (PCM) of voice frequencies on an 64 kbps channel.
G.721 - 32 kbit/s adaptive differential pulse code modulation (ADPCM)
G.722 - 7 kHz audio-coding within 64 kbit/s
G.722.1 - Coding at 24 and 32 kbit/s for hands-free operation in systems with low frame loss
G.722.2 - Wideband coding of speech at around 16 kbit/s using adaptive multi-rate wideband (AMR-WB)
G.726 - 40, 32, 24, 16 kbit/s adaptive differential pulse code modulation (ADPCM)
G.727 - 5-, 4-, 3- and 2-bit/sample embedded adaptive differential pulse code modulation (ADPCM)
G.728 - Coding of speech at 16 kbit/s using low-delay code excited linear prediction
G.729 - Coding of speech at 8 kbit/s using conjugate-structure algebraic-code-excited linear-prediction (CS-ACELP)
Protocol Structure - G.7xx: Audio (Voice) Compression Protocols (CODEC) (G.711, G.721, G.722, G.726, G.727, G.728, G.729) Comparison of major Audio Codec:
|
Name |
standardized by |
description |
bit rate (kb/s) |
sampling rate (kHz) |
|
(ADPCM) DVI |
Intel, IMA |
ADPCM |
32 |
8 |
|
G.711 |
ITU-T |
Pulse code modulation (PCM) |
64 |
8 |
|
G.721 |
ITU-T |
Adaptive differential pulse code modulation (ADPCM) |
32 |
8 |
|
G.722 |
ITU-T |
7 kHz audio-coding within 64 kbit/s |
64 |
16 |
|
G.722.1 |
ITU-T |
Coding at 24 and 32 kbit/s for hands-free operation in systems with low frame loss |
24/32 |
16 |
|
G.723 |
ITU-T |
Extensions of Recommendation G.721 adaptive differential pulse code modulation to 24 and 40 kbit/s for digital circuit multiplication equipment application |
24/40 |
8 |
|
G.723.1 |
ITU-T |
Dual rate speech coder for multimedia communications transmitting at 5.3 and 6.3 kbit/s |
5.6/6.3 |
8 |
|
G.726 |
ITU-T |
40, 32, 24, 16 kbit/s adaptive differential pulse code modulation (ADPCM) |
16/24/32/40 |
8 |
|
G.727 |
ITU-T |
5-, 4-, 3- and 2-bit/sample embedded adaptive differential pulse code modulation (ADPCM) |
var. |
? |
|
G.728 |
ITU-T |
Coding of speech at 16 kbit/s using low-delay code excited linear prediction |
16 |
8 |
|
G.729 |
ITU-T |
Coding of speech at 8 kbit/s using conjugate-structure algebraic-code-excited linear-prediction (CS-ACELP) |
8 |
8 |
|
GSM 06.10 |
ETSI |
Regular Pulse Excitation Long Term Predictor (RPE-LTP) |
13 |
8 |
Related Protocols
RTSP , RTP , RTCP , H.323 , H.245 , H.263
Sponsor Source
G.7xx is a suite of ITU-T (http://www.itu.int/ITU-T/ ) standard.
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