Robust Advanced Low Complexity Waveform Interpolation (RALCWI) is a low bit-rate algorithm for vocoder

Vocoder

A vocoder is an analysis/synthesis system, mostly used for speech. In the encoder, the input is passed through a multiband filter, each band is passed through an envelope follower, and the control signals from the envelope followers are communicated to the decoder...

 implementation; licensed to Spirit DSP

SPIRIT DSP

SPIRIT DSP develops embedded software solutions for real-time voice and video communication over IP networks – voice and video engines.- Products and Solutions :...

.

RALCWI technology uses unique proprietary signal decomposition and parameter encoding methods, ensuring high voice quality at high compression ratios. The voice quality of RALCWI-class Vocoders, as estimated by independent listeners, is similar to that provided by standard Vocoders running at bit rates above 4000 bps. The Mean Opinion Score

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 ...

 (MOS) of voice quality for this Vocoder is about 3.5-3.6. This value was determined by a paired comparison method, performing listening tests of developed and standard voice Vocoders.

The RALCWI Vocoder

Vocoder

A vocoder is an analysis/synthesis system, mostly used for speech. In the encoder, the input is passed through a multiband filter, each band is passed through an envelope follower, and the control signals from the envelope followers are communicated to the decoder...

 operates on a “frame-by-frame” basis. The 20ms source voice frame consists of 160 samples of linear 16-bit PCM sampled at 8 kHz. The Voice Encoder performs voice analysis at the high time resolution (8 times per frame) and forms a set of estimated parameters for each voice segment. All of the estimated parameters are quantized to produce 41-, 48- or 55-bit frames, using Vector Quantization

Vector quantization

Vector quantization is a classical quantization technique from signal processing which allows the modeling of probability density functions by the distribution of prototype vectors. It was originally used for data compression. It works by dividing a large set of points into groups having...

 (VQ) of different types. All of the vector quantizers were trained on a mixed multi-language voice base, which contains voice samples in both Eastern and Western languages.

History

Waveform-Interpolative (WI) vocoder was developed in AT&T Bell Laboratories around 1995 by W.B. Kleijn, and subsequently a low- complexity version was developed by AT&T for the DoD secure vocoder competition. Notable enhancements to the WI coder were made at UCSB. AT&T holds the core patents related to WI, and other institutes hold additional patents. Using these patents as a part of WI coder implementation requires licensing from all IPR holders.

The product is the result of a co-operation between CML Microcircuits and SPIRIT DSP. The co-operation combines CML’s 39-year history of developing mixed-signal semiconductors for professional and leisure communication applications, with SPIRIT’s experience in embedded

Embedded system

An embedded system is a computer system designed for specific control functions within a larger system. often with real-time computing constraints. It is embedded as part of a complete device often including hardware and mechanical parts. By contrast, a general-purpose computer, such as a personal...

 voice products.

Since inception in 1992 SPIRIT is a Russian company that implements mostly standard audio and data communication software products, primarily outside the US.

Founded in 1968, CML Microcircuits are involved in the design, development and supply of low-power analogue, digital and mixed-signal semiconductors

Semiconductor

A semiconductor is a material with electrical conductivity due to electron flow intermediate in magnitude between that of a conductor and an insulator. This means a conductivity roughly in the range of 103 to 10−8 siemens per centimeter...

 for telecommunications systems worldwide. CML IC’s, the CMX608, CMX618 and the CMX638 market to worldwide communication markets based upon SPIRIT’s

SPIRIT DSP

SPIRIT DSP develops embedded software solutions for real-time voice and video communication over IP networks – voice and video engines.- Products and Solutions :...

 proprietary Low Bit-Rate Vocoder

Vocoder

A vocoder is an analysis/synthesis system, mostly used for speech. In the encoder, the input is passed through a multiband filter, each band is passed through an envelope follower, and the control signals from the envelope followers are communicated to the decoder...

 technology.

Applications

• Terminal equipment for Digital Mobile Radio (DMR)
  Embedded system
  An embedded system is a computer system designed for specific control functions within a larger system. often with real-time computing constraints. It is embedded as part of a complete device often including hardware and mechanical parts. By contrast, a general-purpose computer, such as a personal...
  
   based systems.
• Digital Trunking
• DMR TDMA
• Digital Voice Scrambling and Encryption
• Digital WLL
  Wireless local loop
  Wireless local loop , is a term for the use of a wireless communications link as the "last mile / first mile" connection for delivering plain old telephone service and/or broadband Internet to telecommunications customers....
  
  
• Voice Storage and Playback Systems
• Messaging Systems
• VoIP Systems
• Voice Pagers
• Regenerative Digital Voice Repeaters