News
TWELP 400 bps Vocoder Updating
- Details
We have significantly improved the speech quality and intelligibility of our TWELP 400 bps vocoder. The updated version now delivers MELPe 600-class performance at just two-thirds of the bitrate, while achieving higher PESQ, STOI and ESTOI scores and comparable ASR-based intelligibility.
These results further demonstrate the efficiency of TWELP technology for bandwidth-constrained voice communication, delivering high speech quality and intelligibility at an exceptionally low 400 bps bitrate.
TWELP 1200 bps Vocoder Updating
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The updated TWELP 1200 bps vocoder further improves speech quality and intelligibility, reinforcing one of the key advantages of TWELP technology: high-quality voice communication at half the bitrate of conventional 2400 bps solutions.
In practical systems, this can double the number of voice channels within the same available bandwidth, while delivering speech that sounds more natural and less synthetic.
ASR Intelligibility Testing
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Since early 2026, we have added an ASR-based speech intelligibility evaluation using whisper.cpp to our existing PESQ, STOI, and ESTOI measurements.
This new metric provides an additional practical measure of speech intelligibility for low-bitrate vocoders and complements the traditional objective quality and intelligibility metrics we already use.
We are gradually updating all vocoder pages on our website to include results from this new evaluation method, together with links to detailed test reports.