G.723.1
Encyclopedia
G.723.1 is an audio codec
Codec
A codec is a device or computer program capable of encoding or decoding a digital data stream or signal. The word codec is a portmanteau of "compressor-decompressor" or, more commonly, "coder-decoder"...

 for voice that compresses voice audio in 30 ms frames. An algorithmic look-ahead of 7.5 ms duration means that total algorithmic delay is 37.5 ms. Its official name is Dual rate speech coder for multimedia communications transmitting at 5.3 and 6.3 kbit/s.

Note that this is a completely different codec from G.723
G.723
G.723 is a ITU-T standard speech codec using extensions of G.721 providing voice quality covering 300 Hz to 3400 Hz using Adaptive Differential Pulse Code Modulation to 24 and 40 kbit/s for digital circuit multiplication equipment applications...

.

There are two bit rate
Bit rate
In telecommunications and computing, bit rate is the number of bits that are conveyed or processed per unit of time....

s at which G.723.1 can operate:
  • 6.3 kbit/s (using 24 byte frames) using a MPC-MLQ algorithm (MOS
    Mean Opinion Score
    The Mean Opinion Score test has been used for decades in telephony networks to obtain the human user's view of the quality of the network. In multimedia especially when codecs are used to compress the bandwidth requirement , the mean opinion score ...

     3.9)
  • 5.3 kbit/s (using 20 byte frames) using an ACELP
    ACELP
    Algebraic code-excited linear prediction is a patented speech coding algorithm by VoiceAge Corporation in which a limited set of pulses is distributed as excitation to linear prediction filter....

     algorithm (MOS
    Mean Opinion Score
    The Mean Opinion Score test has been used for decades in telephony networks to obtain the human user's view of the quality of the network. In multimedia especially when codecs are used to compress the bandwidth requirement , the mean opinion score ...

     3.62)

Use

G.723.1 is mostly used in Voice over IP (VoIP) applications due to its low bandwidth requirement. Music or tones such as DTMF or fax
Fax
Fax , sometimes called telecopying, is the telephonic transmission of scanned printed material , normally to a telephone number connected to a printer or other output device...

 tones cannot be transported reliably with this codec, and thus some other method such as G.711
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. Its formal name is Pulse code modulation of voice frequencies. It is required standard in many technologies, for example in H.320 and H.323 specifications. It can also...

 or out-of-band methods should be used to transport these signals. The complexity of the algorithm is below 16 MIPS. 2.2 kilobytes of RAM is needed for codebooks.

G.723.1 is a required audio codec in the H.324
H.324
H.324 is an ITU-T recommendation for voice, video and data transmission over regular analog phone lines. It uses a regular 33,600 bit/s modem for transmission, the H.263 codec for video encoding and G.723.1 for audio....

 ITU-T recommendation for H.324 terminals offering audio communication. In 3GPP
3GPP
The 3rd Generation Partnership Project is a collaboration between groups of telecommunications associations, known as the Organizational Partners...

 3G-324M
3G-324M
3G-324M is the 3GPP umbrella protocol for video telephony in 3G mobile networks.The 3G-324M protocol operates over an established circuit switched connection between two...

 specification support for G.723.1 is not mandatory, but recommended.

Features

  • Sampling frequency 8 kHz/16-bit (240 samples for 30 ms frames)
  • Fixed bit rate (5.3 kbit/s with 20 byte 30 ms frames, 6.3 kbit/s with 24 byte 30 ms frames)
  • Fixed frame size for each rate (5.3 kbit/s with 20 byte 30 ms frames, 6.3 kbit/s with 24 byte 30 ms frames)
  • Algorithmic delay is 37.5 ms per frame, with 7,5 ms look-ahead delay
  • G.723 is a hybrid speech coder, with high bit rate using Multi-Pulse Maximum Likelihood Quantization (MP-MLQ) and low bit rate using Algebraic Code Excited Linear Prediction (ACELP)
  • The complexity of the algorithm is rated at 25, using a relative scale where G.711
    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. Its formal name is Pulse code modulation of voice frequencies. It is required standard in many technologies, for example in H.320 and H.323 specifications. It can also...

     is 1 and G.729a is 15.
  • G.723.1 Annex A defines 4 byte Silence Insertion Descriptor (SID) frame for Comfort Noise Generation
    Comfort noise
    Comfort noise is synthetic background noise used in radio and wireless communications to fill the artificial silence in a transmission resulting from voice activity detection or from the audio clarity of modern digital lines....

  • PSQM
    PSQM
    PSQM is a computational and modeling algorithm defined in ITU Recommendation ITU-T P.861 that objectively evaluates and quantifies voice quality of voice-band speech codecs....

     testing under ideal conditions yields Mean Opinion Scores
    Mean Opinion Score
    The Mean Opinion Score test has been used for decades in telephony networks to obtain the human user's view of the quality of the network. In multimedia especially when codecs are used to compress the bandwidth requirement , the mean opinion score ...

     of 4.08 for G.723.1 (6.3 kbit/s), compared to 4.45 for G.711
    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. Its formal name is Pulse code modulation of voice frequencies. It is required standard in many technologies, for example in H.320 and H.323 specifications. It can also...

     (μ-law)
  • PSQM
    PSQM
    PSQM is a computational and modeling algorithm defined in ITU Recommendation ITU-T P.861 that objectively evaluates and quantifies voice quality of voice-band speech codecs....

     testing under network stress yields Mean Opinion Scores
    Mean Opinion Score
    The Mean Opinion Score test has been used for decades in telephony networks to obtain the human user's view of the quality of the network. In multimedia especially when codecs are used to compress the bandwidth requirement , the mean opinion score ...

     of 3.57 for G.723.1 (6.3 kbit/s), compared to 4.13 for G.711
    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. Its formal name is Pulse code modulation of voice frequencies. It is required standard in many technologies, for example in H.320 and H.323 specifications. It can also...

     (μ-law)

Licensing

Use of G.723.1 requires a license for the patents that cover the algorithm. The last patent will expire in 2014.

The authorized intellectual property rights (IPR) Licensing Administrator for G.723.1 technology is Sipro Lab Telecom.

Members of the G.723.1 patent pool
Patent pool
In patent law, a patent pool is a consortium of at least two companies agreeing to cross-license patents relating to a particular technology. The creation of a patent pool can save patentees and licensees time and money, and, in case of blocking patents, it may also be the only reasonable method...

 are AudioCodes
AudioCodes
AudioCodes Ltd. designs, develops, and sells products for voice, data, and video over IP networks. The company is an early pioneer of the VoIP industry having shipped VoIP solutions as early as 1995.-Company history:...

, France Telecom
France Télécom
France Telecom S.A. is the main telecommunications company in France, the third-largest in Europe and one of the largest in the world. It currently employs about 180,000 people and has 192.7 million customers worldwide . In 2010 the group had revenue of €45.5 billion...

, Université de Sherbrooke
Université de Sherbrooke
The Université de Sherbrooke is a large university with campuses located in Sherbrooke, Quebec, Canada and Longueuil, a suburb of Montreal approximately west of Sherbrooke. It is one of two universities, and the only French language university, in the Estrie region of Quebec.In 2007, the...

, Nippon Telegraph and Telephone Corporation and Nokia
Nokia
Nokia Corporation is a Finnish multinational communications corporation that is headquartered in Keilaniemi, Espoo, a city neighbouring Finland's capital Helsinki...

.

External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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