RALCWI(Robust Advanced Low Complexity Waveform Interpolation):
Robust Advanced Low Complexity Waveform Interpolation (RALCWI) is a low bit-rate algorithm for vocoder implementation.licensed to Spirit DSP.
full rate at 4 kbit/s
全速率下：3.5~3.6 MOS分
他是一种基于波形内插法的语音编码器。
（Waveform-Interpolative (WI) vocoder was developed in AT&T Bell Laboratories around 1995 by W.B. Kleijn）
Kleijn, W.B.; Haagen, J.; AT&T Bell Labs., Murray Hill, NJ ,"A speech coder based on decomposition of characteristic waveforms," IEEE 1995 International Conference on Acoustics, Speech, and Signal Processing, 1995. ICASSP-95.
Kleijn, W.B.; Shoham, Y.; Sen, D.; Hagen, R.; AT&T Bell Labs., Murray Hill, NJ "A low-complexity waveform interpolation coder," IEEE ICASSP 1996.
Gottesman, O.; Gersho, A.; Dept. of Electr. & Comput. Eng., California Univ., Santa Barbara, CA , "Enhanced waveform interpolative coding at low bit-rate," IEEE Transactions on Speech and Audio Processing, November 2001.
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ALCWI, a new class of speech codecs developed by SPIRIT, opens up
a new level of quality, providing Near-Toll Quality speech at low bit
rates in the range of 2000 to 4000 bps and even lower.
Until recently, this level of speech quality couldn’t be achieved at bit
rates lower than 4000 bps. Now this is possible by virtue of new and
efficient speech coding technology developed by SPIRIT.
The new technology is similar to the Waveform Interpolation
(WI) model, where the signal is decomposed into two components
(SEW and REW), which are then encoded separately. However, the
new SPIRIT technology uses unique proprietary signal decomposition
and parameter encoding methods, ensuring high speech quality at high
compression ratios, while requiring low computing resources.
The speech quality of ALCWI-class codecs, as estimated by
independent listeners, is similar to that provided by standard codecs
running at bit rates above 4000 bps, while the computational
complexity is only slightly increased in comparison with the complexity
of other widely used codecs running at similar bit rates.
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