| G.711 |
PCM |
64, 56 |
A ITU (International Telecommunications Union) standard for a narrow-band audio codec that encodes speech into a stream of 8 bit samples (or less frequently 7 bit samples) at 8khz. This creates a data stream at either 64kbps or 56kbps. G.711 uses a logarithmic mapping that emphasizes the parts of the signal that the human ear is most sensitive to. Uses pulse code modulation
There are two variants of G.711:
- uLaw - Used with T1 and J1 connections
- aLaw - used with E1 connections (Europe and Australia)
High quality, high bandwidth
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| G.722 |
ADPCM |
48-64 |
A ITU standard wideband speech codec.
G.722.1 offers low bit-rate compressions.
G.722.2, also known as AMR-WB (Adaptive Multirate Wideband), offers even lower bit-rate compressions and the the ability to vary compressions as the network topography changes. For example bandwidth is automatically conserved when network congestion is high. When congestion returns to a normal level, a lower-compression, higher-quality bit rate is restored.
G.722 and its variants sample audio data at a rate of 16 kHz, double that of traditional telephony interfaces, which results in superior audio quality and clarity.
G.722 patents have expired, so it is freely available.
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| G.723.1 |
ACELP
MP-MLQ |
5.3
6.3 |
A ITU standard for a narrow-band audio codec that encodes speech into a stream of data frames that each represents 30ms (240 samples) of speech data. Each frame can be either 24 or 20 bytes long, which makes the data stream either 6.4kbps or 5.3kbps.
License fee to use this Codec commercially.
Lower quality and < 10% of bandwidth used by G.711. (Less bandwidth = more delay)
Uses MP-MLQ (Multi-Pulse Maximum Likelihood Quantization)
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| G.726 |
ADPCM |
40, 32,
24, 16 |
A ITU standard for a narrow-band audio codec that encodes speech into a stream of 2, 3, 4, or 5 bit samples - data stream = 16kbps, 24kbps, 32kbps, or 40kbps.
Uses ADPCM (Adaptive differential pulse code modulation.
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| G.728 |
LD-CELP |
16 |
A ITU standard for a narrow-band audio codec that encodes speech into a stream of 10 bit frames that each represent 5 samples - data stream = 16kbps. License fee to use this Codec commercially.
Uses CS-ACELP (Conjugate-structure algebraic-code-excited linear prediction speech coder).
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| G.729 |
CS-ACELP |
8 |
A ITU standard for a narrow-band audio codec that encodes speech into a stream of data frames that each represent 10ms (80 samples) of speech data. Each frame is 10 bytes - data stream = 8kbps. License fee to use this Codec commercially.
Uses CS-ACELP (Conjugate-structure algebraic-code-excited linear prediction speech coder).
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GSM
06.10 |
PCM |
13.2 |
A narrow-band audio codec that encodes speech into a stream of data frames that each represent 20ms (160 samples) of speech data. Each frame is 264 bits, giving a data stream of 13.2kbps. |