WARNING!
This page contains information about the previous version (4.0).
The current version (5.0) provides significantly improved speech quality.
We will update the information in the near future.

Includes a few modes (bit rates): 3600, 2400, 1600, 1200, 700, 600, 600/900 (scalable), 480/800 (scalable), 480, 300 bps as well as NRT mode (variable bit rate).

Of course, quantity and presence of the bit rates can be modified under specific requirements of customer.

Provides very high speech quality - much better in comparison with any competitors on the market.

For Digital HF Radio and other markets.

TWELP Technology Features. The vocoder is based on newest technology of speech coding called "Tri-Wave Excited Linear Prediction" (TWELP) that was developed by experts of DSPINI. 

TWELP technology is a new class of vocoders that differs from any other LPC-based vocoders by:

• advance reliable method of pitch estimation
• pitch-synchronous analysis
• advance tri-wave model of excitation
• newest quantization schemes
• pitch-synchronous synthesis

Thanks to these unique features, TWELP technology provides much better speech quality in comparison with any well-known technologies, including AMBE+2, MELPe, ACELP, etc. on the same bit rate in range from 300 bps up to 9600 bps and more.

TWELP technology allowes to reduce bit rate two times in practice. Moreover, TWELP vocoder sounds much more naturally and in contrast to other LBR vocoders (like MELPe, etc.) TWELP provides much better quality for non-speech signals like sirens, background music, etc.

Superiority In Speech Quality. Here is the comparison with MELPe and GSM AMR vocoders in noiseless channel. TWELP 2400 bps vocoder, MELPe 2400 bps vocoder and GSM AMR 4.75 kbps vocoder were tested, 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:

Please find infomation about superiority in speech quality of the TWELP MR vocoder for all other bit rates on appropriate web-pages for specific bit rates.

Speech Samples (WAV-files). A few independent experts listened TWELP 2400 bps vocoder in comparison with MELPe 2400 bps vocoder and GSM AMR 4750 bps vocoder, using preference method. All experts preferred TWELP to the MELPe, having noted much more natural human-sounding of voice in the TWELP vocoder. A majority of experts haven't given preferences to GSM AMR or TWELP, but a majority of the remained prefered TWELP, having noted more clear sounding of speech in TWELP vocoder.
You can play and listen short samples of the source speech as well as the speech processed by these vocoders for any of 20 languages, using links in the table below.
Also, you can download full set of the P.50 samples as zip-files for all languages simultaneously, using the links in the "Downloads" para in a bottom of the page.

Please find samples of the TWELP MR vocoder for all other bit rates on appropriate web-pages for specific bit rates.

Superiority In Quality Of The Non-speech Signals. In contrast to other LBR vocoders (MELPe, AMBE+2, etc.), TWELP vocoders provide 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 vocoders 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.

Please find non-speech samples of the TWELP MR vocoder for all other bit rates on appropriate web-pages for specific bit rates.

High Robustness To Acoustic Noise. In contrast to other LBR vocoders, TWELP vocoders are well robust to acoustic noise thanks to robust reliable method of pitch estimation and other features of TWELP technology.

Moreover, vocoder includes in-built Noise Cancellation—Speech Enhancement (NCSE) functionality that improves speech quality in noisy acoustic environment.

Please find similar samples of the TWELP MR vocoder for all other bit rates on appropriate web-pages for specific bit rates.

High Robustness To The Channel Errors. The diagram and table below show a dependence of the averaged speech quality for AWGN-noisy channel for different BER in comparison with other vocoders.

We recommend to use regular versions of the TWELP vocoders in good channels only, where BER is not more than 0.15%.

In case you use the channels, where a majority of calls are at BER > 0.15%, we recommend to use "TWELP Robust" versions of the vocoders (with in-built specific FEC) and primeraly with "Soft Decisions" output from a modem. You can compare the robustness of the vocoders on the diagramm below.

You can play and listen short samples of the source speech as well as the speech processed by MELPe and TWELP Robust vocoders on the same bit rate 2400 bps in AWGN channel with BER = 5% for any of 20 languages, using links in the table below.

Please find information about robustness to errors of the TWELP MR vocoder for all other bit rates on appropriate web-pages for specific bit rates.

Additional Functionalities. The following additional functionalities are developed by DSPINI and integrated into TWELP vocoders:

• Automatic Gain Control (AGC),
• Noise Cancellation for Speech Enhancement (NCSE)
• Voice Activity Detector (VAD),
• Tone Detection/Generation (Single tones and Dual tones). The tones are transmitted by the vocoder facilities.

Each functionality has unique features, performance and characteristics, providing significant superiority over any well-known implementations on the market.

Technical Characteristics And Resource Requirements:

Resources for TI's DSP C55 platform are available on request

* DSPINI continues optimization of the TWELP algorithm and code in order to minimize computational complexity of the vocoder.

Vulnerability / Security. DSPINI guarantees ABSOLUTE cleanliness of the software from any undocumented features, undeclared capabilities, etc. All our customers can be sure that any our software/ code doesn't contain any secret functions and features hidden from user. We are ready to provide source codes of our software products for an appropriate certification if need.

Guarantee And Support.  DSPINI guarantees a quality and accordance of all technical characteristics of the product to requirement of current specifications. Testing and other method of quality control are used for guarantee support.

Any Platforms.  DSPINI can port this vocoder software into any other DSP, RISC or general- purposes platform inshort time: 1-2 months.

Licensing Terms.  To use the vocoder, customer should obtain a license from DSPINI only.

Customization.  The vocoder can be customized under any specific requirements- other bit rate, frame size, any other robustness to channel errors, etc. Please contact with us for details.

Prospects.  DSPINI is impoving and developing continuously a set of new vocoders with range from 300 bps up to 9600 bps, based on TWELP technology.

Related Software.  This vocoder may be effectively used in a bundle with other DSPINI's products:

• Linear and acoustic echo cancellers,
• Multichannel noise cancellers (including two-microphone adaptive array),
• Wired or radiomodems for any types of channels and bitrates,
• Other products.

Downloads:

• Datasheet (pdf)
• ITU-T P.50 source speech samples (zip)
• AMBE+2 2450 bps speech samples (zip)
• MELPe 2400 bps speech samples (zip)
• TWELP 2400 bps speech samples (zip)
• PC-evaluation package (zip) — on request
• User's Guide document (pdf) — on request