- Advance reliable method of Pitch estimation
- Pitch synchronous analysis
- Advance tri-wave model of excitation:
o Voiced Component Excited Wave (VCEW)
o Unvoiced Component Excited Wave (UCEW)
o Transient Component Excited Wave (TCEW)
- Newest quantization schemes
- Pitch synchronous synthesis
DSPINI has tested TWELP 2400 bps vocoder and AMBE-3000 HDK (Rate#33: AMBE+2 2450 bps vocoder), using ITU-T P.50 speech base for 20 different languages. ITU-T P.862 utility was used for estimation of the speech quality in PESQ terms.
The test demonstrated significant superiority of TWELP over AMBE+2 in speech quality (in average more than 0.1 PESQ) (see the diagram). Also these results are confirmed by independent listeners, which were asked to compare the vocoders by ear.
In contrast to other LPC-based LBR vocoders, TWELP vocoder provides high quality of non-speech signals, including police, ambulance, fire sirens, etc. This feature in conjunction with high quality natural human-sounding of voice makes TWELP vocoder well suitable for replacement of analog radio by digital radio and also for other applications, where high quality transmitting of non-speech signals is relevant along with high quality transmitting of speech signals.
Another benefit over other LPC-based LBR vocoders is that TWELP vocoder is well robust to acoustic noise thanks to robust reliable method of pitch estimation and other features of TWELP technology.
TWELP 3600 bps vocoder includes FEC (1200 bps) that is integrated with vocoder (2400 bps) on base of “joint source-channel coding” approach that provides high speech quality simultaneously in noisy channel as well as in noiseless channel. FEC can operate with “soft decisions” as well as with ”hard decisions” from a modem. Mode of “soft decisions” provides much better robustness in comparison with mode of “hard decisions”.
The vocoder has such integrated additional functionalities, as Automatic Gain Control (AGC), Noise Cancellation for Speech Enhancement (NCSE) that improves quality of noisy speech more than on 0.1 PESQ, Voice Activity Detector (VAD), Tone Detection/Generation (Single tones and Dual tones) (the tones are transmitted through the vocoder).
Bitrates from 600 bps up to 9600 bps of TWELP vocoder from DSPINI are expected to release throughout 2011 and 2012.
TWELP is available for evaluation on request at DSPINI.
Detailed information on TWELP (diagrams, characteristics, etc.) here: www.twelp.ru
DSP Innovations Inc. is a supplier of DSP-software and engineering services on world market. Proprietary and standard vocoders (speech codecs) from DSPINI have superior characteristics, operate in range from 300 bps up to 64 kbps bit rates and are used all over the world in: Secure Voice, Software Defined Radio, Wireless, VoIP, Voice Storage, etc.
The mainstream is speech technologies and voice communication:
DSP INNOVATIONS INC.
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