G.722
Encyclopedia
G.722 is a ITU-T
standard 7 kHz wideband speech codec
operating at 48, 56 and 64 kbit/s. It was approved by ITU-T in November 1988. Technology of the codec is based on sub-band ADPCM (SB-ADPCM).
G.722 sample audio data at a rate of 16 kHz (using 14 bits), double that of traditional telephony interfaces, which results in superior audio quality and clarity.
Other ITU-T 7 kHz wideband codecs include G.722.1
and G.722.2. These codecs are not variants of G.722 and they use different patented compression technologies. G.722.1 is based on Siren
codecs and offers lower bit-rate compressions. A more recent G.722.2, also known as AMR-WB
("Adaptive Multirate Wideband") is based on ACELP
and offers even lower bit-rate compressions, as well as the ability to quickly adapt to varying compressions as the network topography mutates. In the latter case, bandwidth is automatically conserved when network congestion is high. When congestion returns to a normal level, a lower-compression, higher-quality bitrate is restored.
applications, such as on a local area network
where network bandwidth is readily available, and offers a significant improvement in speech quality over older narrowband codecs such as G.711
, without an excessive increase in implementation complexity. Environments where bandwidth is more constrained may prefer one of the more bit-efficient codecs, such as G.722.1 (Siren7) or G.722.2 (AMR-WB).
G.722 is also widely used by broadcasters for sending commentary grade audio over a single 64 kbit/s ISDN B channel.
payload type 9.
Note that IANA
records the clock rate for type 9 G.722 as 8 kHz (instead of 16 kHz), RFC3551 clarifies that this is due to a historical error and is retained in order to maintain backward compatibility. Consequently correct implementations represent the value 8,000 where required but encode and decode audio at 16 kHz.
Whilst G.722 allows for bitrates of 64, 56 and 48 kbit/s, in practice, data is encoded at 64 kbit/s, with bits from the lower sub-band being used to encode auxiliary data. The greater the number of bits allocated to aux data, the lower the bit rate.
G722 specification
ITU-T
The ITU Telecommunication Standardization Sector is one of the three sectors of the International Telecommunication Union ; it coordinates standards for telecommunications....
standard 7 kHz wideband speech 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"...
operating at 48, 56 and 64 kbit/s. It was approved by ITU-T in November 1988. Technology of the codec is based on sub-band ADPCM (SB-ADPCM).
G.722 sample audio data at a rate of 16 kHz (using 14 bits), double that of traditional telephony interfaces, which results in superior audio quality and clarity.
Other ITU-T 7 kHz wideband codecs include G.722.1
G.722.1
G.722.1 is a licensed royalty-free ITU-T standard audio codec providing high quality, moderate bit rate wideband G.722.1 is a licensed royalty-free ITU-T standard audio codec providing high quality, moderate bit rate (24 and 32 kbit/s) wideband G.722.1 is a licensed royalty-free ITU-T standard...
and G.722.2. These codecs are not variants of G.722 and they use different patented compression technologies. G.722.1 is based on Siren
Siren Codec
Siren is a family of patented, transform-based, wideband audio codecs developed and licensed by PictureTel Corporation . There are three Siren codecs: Siren 7, Siren 14 and Siren 22....
codecs and offers lower bit-rate compressions. A more recent G.722.2, also known as AMR-WB
AMR-WB
Adaptive Multi-Rate Wideband is a patented speech coding standard developed based on Adaptive Multi-Rate encoding, using similar methodology as Algebraic Code Excited Linear Prediction...
("Adaptive Multirate Wideband") is based on 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....
and offers even lower bit-rate compressions, as well as the ability to quickly adapt to varying compressions as the network topography mutates. In the latter case, bandwidth is automatically conserved when network congestion is high. When congestion returns to a normal level, a lower-compression, higher-quality bitrate is restored.
Applications
G.722 is an ITU standard codec that provides 7 kHz wideband audio at data rates from 48, 56 and 64 kbit/s. This is useful for voice over IPVoice over IP
Voice over Internet Protocol is a family of technologies, methodologies, communication protocols, and transmission techniques for the delivery of voice communications and multimedia sessions over Internet Protocol networks, such as the Internet...
applications, such as on a local area network
Local area network
A local area network is a computer network that interconnects computers in a limited area such as a home, school, computer laboratory, or office building...
where network bandwidth is readily available, and offers a significant improvement in speech quality over older narrowband codecs 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...
, without an excessive increase in implementation complexity. Environments where bandwidth is more constrained may prefer one of the more bit-efficient codecs, such as G.722.1 (Siren7) or G.722.2 (AMR-WB).
G.722 is also widely used by broadcasters for sending commentary grade audio over a single 64 kbit/s ISDN B channel.
RTP Encapsulation
G.722 VoIP is typically carried in RTPReal-time Transport Protocol
The Real-time Transport Protocol defines a standardized packet format for delivering audio and video over IP networks. RTP is used extensively in communication and entertainment systems that involve streaming media, such as telephony, video teleconference applications, television services and...
payload type 9.
Note that IANA
Internet Assigned Numbers Authority
The Internet Assigned Numbers Authority is the entity that oversees global IP address allocation, autonomous system number allocation, root zone management in the Domain Name System , media types, and other Internet Protocol-related symbols and numbers...
records the clock rate for type 9 G.722 as 8 kHz (instead of 16 kHz), RFC3551 clarifies that this is due to a historical error and is retained in order to maintain backward compatibility. Consequently correct implementations represent the value 8,000 where required but encode and decode audio at 16 kHz.
Whilst G.722 allows for bitrates of 64, 56 and 48 kbit/s, in practice, data is encoded at 64 kbit/s, with bits from the lower sub-band being used to encode auxiliary data. The greater the number of bits allocated to aux data, the lower the bit rate.
Licensing
G.722 patents have expired, so it is freely available.G722 specification