VMR-WB
Encyclopedia
Variable-Rate Multimode Wideband (VMR-WB) is a source-controlled variable-rate multimode codec
designed for robust encoding/decoding of wideband/narrowband speech. The operation of VMR-WB is controlled by speech signal characteristics (i.e., source-controlled) and by traffic condition of the network (i.e., network-controlled mode switching). Depending on the traffic conditions and the desired quality of service (QoS
), one of the 4 operational modes is used. All operating modes of the existing VMR-WB standard are fully compliant with cdma2000
rate-set II. VMR-WB modes 0, 1, and 2 are cdma2000 native modes with mode 0 providing the highest quality and mode 2 the lowest ADR. VMR-WB mode 3 is the AMR-WB
interoperable mode operating at an ADR slightly higher than mode 0 and providing a quality equal or better than that of AMR-WB at 12.65 kbit/s when in an interoperable interconnection with AMR-WB at 12.65 kbit/s.
Now also a cdma2000 rate-set I compliant mode is implemented to the coder as mode 4. The average bitrate of the mode is 6.1 kbit/s (maximum is 8.55 kbit/s). Source coding bitrates are: Rate-Set I - 8.55, 4.0, 2.0, 0.8 kbps, Rate-Set II - 13.3, 6.2, 2.7, 1.0 kbps. VMR-WB uses 16 kHz sampling frequency. Algorithmic delay is 33.75ms.
VMR-WB can be also used in 3GPP2 container file format - 3G2
.
VMR-WB was designed by Nokia
and VoiceAge. It is based on AMR-WB.
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"...
designed for robust encoding/decoding of wideband/narrowband speech. The operation of VMR-WB is controlled by speech signal characteristics (i.e., source-controlled) and by traffic condition of the network (i.e., network-controlled mode switching). Depending on the traffic conditions and the desired quality of service (QoS
Quality of service
The quality of service refers to several related aspects of telephony and computer networks that allow the transport of traffic with special requirements...
), one of the 4 operational modes is used. All operating modes of the existing VMR-WB standard are fully compliant with cdma2000
CDMA2000
CDMA2000 is a family of 3G mobile technology standards, which use CDMA channel access, to send voice, data, and signaling data between mobile phones and cell sites. The set of standards includes: CDMA2000 1X, CDMA2000 EV-DO Rev. 0, CDMA2000 EV-DO Rev. A, and CDMA2000 EV-DO Rev. B...
rate-set II. VMR-WB modes 0, 1, and 2 are cdma2000 native modes with mode 0 providing the highest quality and mode 2 the lowest ADR. VMR-WB mode 3 is the 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...
interoperable mode operating at an ADR slightly higher than mode 0 and providing a quality equal or better than that of AMR-WB at 12.65 kbit/s when in an interoperable interconnection with AMR-WB at 12.65 kbit/s.
Now also a cdma2000 rate-set I compliant mode is implemented to the coder as mode 4. The average bitrate of the mode is 6.1 kbit/s (maximum is 8.55 kbit/s). Source coding bitrates are: Rate-Set I - 8.55, 4.0, 2.0, 0.8 kbps, Rate-Set II - 13.3, 6.2, 2.7, 1.0 kbps. VMR-WB uses 16 kHz sampling frequency. Algorithmic delay is 33.75ms.
VMR-WB can be also used in 3GPP2 container file format - 3G2
3GP
3GP is a multimedia container format defined by the Third Generation Partnership Project for 3G UMTS multimedia services. It is used on 3G mobile phones but can also be played on some 2G and 4G phones....
.
VMR-WB was designed by Nokia
Nokia
Nokia Corporation is a Finnish multinational communications corporation that is headquartered in Keilaniemi, Espoo, a city neighbouring Finland's capital Helsinki...
and VoiceAge. It is based on AMR-WB.
External links
- 3GPP2 specification
- RFC 4424 - Real-Time Transport Protocol (RTP) Payload Format for the Variable-Rate Multimode Wideband (VMR-WB) Extension Audio Codec
- RFC 4348 - Real-Time Transport Protocol (RTP) Payload Format for the Variable-Rate Multimode Wideband (VMR-WB) Audio Codec
- VoiceAge website: VMR-WB — Source-controlled Variable Bit Rate Wideband Compression (archived)
- VoiceAge website