A unique high speech quality for such a very low bit rate — better than MELPe at 600 bps.
For Digital HF Radio and other markets.
TWELP Technology Features. The vocoder is based on the 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 in:
- an advance reliable method of pitch estimation
- a pitch-synchronous analysis
- an advance tri-wave model of excitation
- newest quantization schemes
- a pitch-synchronous synthesis
Thanks to these unique features, TWELP technology provides a much better speech quality in comparison with any well-known technologies, including AMBE+2, MELPe, ACELP, etc. at the same bit rate in the range from 300 bps up to 9600 bps and more. Moreover, in contrast to other LBR vocoders (like MELPe, etc.) TWELP provides a much better quality for non-speech signals like sirens, background music, etc.
Superiority In Speech Quality. Here is a comparison with MELPe vocoder, operating on 600 bps. TWELP 480 bps vocoder and MELPe 600 bps vocoder were tested, using ITU-T P.50 speech base for 20 different languages. ITU-T P.862 utility was used for an estimation of a speech quality in PESQ terms:
|Language||TWELP 480 bps||MELPe 600 bps|
Superiority of the TWELP 480 is on average 0.08 PESQ
Speech Samples (WAV-files). A few independent experts listened to TWELP 480 bps vocoder in comparison with MELPe 600 bps vocoder, using a method of preferences. Majority of experts preferred TWELP to MELPe, having noted a much more natural human-sounding of voice in the TWELP vocoder.
You can play and listen short samples of the source speech as well as the speech processed by both 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.
|Language||Source speech||MELPe 600 bps||TWELP 480 bps|
Superiority In Quality Of The Non-speech Signals. In contrast to other LBR vocoders (MELPe, AMBE+2, etc.), TWELP vocoders provide a high quality of non-speech signals, including police, ambulance, fire sirens, etc. This feature in conjunction with a high quality natural human-sounding of voice makes TWELP vocoders well suitable for replacement of an analog radio by a digital radio and also for other applications where a high quality transmission of non-speech signals is relevant along with a high quality transmission of speech signals.
|Source type||Source signal||MELPe 600 bps||TWELP 480 bps|
High Robustness To Acoustic Noise. In contrast to other LBR vocoders, TWELP vocoders are well robust to acoustic noise thanks to a robust reliable method of a pitch estimation and other features of TWELP technology.
Moreover, vocoder includes in-built Noise Cancellation—Speech Enhancement (NCSE) functionality that improves a speech quality in a noisy acoustic environment.
|NCSE Mode||Source signal||MELPe 600 bps||TWELP 480 bps|
High Robustness To The Channel Errors. The diagram and the table below show a dependence of the averaged speech quality for AWGN-noisy channel on a different BER in comparison with other vocoders.
Special "robust" versions of the TWELP vocoders include FEC that is integrated with the vocoder on base of "joint source-channel coding" approach that provides a high speech quality simultaneously in a noisy channel as well as in a noiseless channel. FEC can operate with "soft decisions" as well as with "hard decisions" from a modem. "Soft decisions" mode provides a much better robustness in comparison with the "hard decisions" mode.
|BER %||MELPe 600||TWELP 600 Robust||TWELP 480|
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 a significant superiority over any well-known implementations on the market.
Technical Characteristics And Resource Requirements:
(including frame size)
|Signal format||Bit stream format|
|Control range:||0 ... +20 dB|
|NCSE||Noise Canceller -
|SNR increasing||> 6 dB|
|> 0.1 PESQ|
|In accordance with the international standards|
|Special generator, kept continuity of a signal
(phase and amplitude of signal of previous frame)
|Reliable detection speech
in a background noise
|Type of noise||"white"|
|Level||- 60 dB|
|Voice Encoder +
|Voice Encoder +
|Voice Encoder +
* DSPINI continues optimization of the TWELP algorithm and the code in order to minimize a computational complexity of the vocoder.
Vulnerability / Security. DSPINI guarantees an ABSOLUTE cleanliness of the software from any undocumented features, undeclared capabilities, etc. All our customers can be sure that none of our software/ code contains secret functions or hiiden features. We are ready to provide the source codes of our software products for an appropriate certification, if needed.
Guarantee And Support. DSPINI guarantees a quality and accordance of all technical characteristics of the product to requirement of the current specifications. Testing and other method of quality control are used for a guarantee support.
Any Platforms. DSPINI can port this vocoder software onto any other DSP, RISC or general-purpose platform in a short 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 the 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.
- Datasheet (pdf)
- ITU-T P.50 source speech samples (zip)
- MELPe 600 bps speech samples (zip)
- TWELP 480 bps speech samples (zip)
- PC-evaluation package (zip) — at request
- User's Guide document (pdf) — at request