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| From | Rafael Deliano <Rafael_Deliano@arcor.de> |
|---|---|
| Newsgroups | comp.arch.embedded |
| Subject | Re: Voice compression |
| Date | 2025-04-05 11:12 +0200 |
| Organization | A noiseless patient Spider |
| Message-ID | <vsqs6f$1t4io$1@dont-email.me> (permalink) |
| References | <vsjotj$14v21$1@dont-email.me> <vsjtmt$2ej99$1@dont-email.me> <vsmhuo$188tp$1@dont-email.me> |
> very poor, quite unusable. You are not seriously expecting me to debug your code ? CVSD 16kBit was used in the 70ies for military secure communication. The then SpaceShuttle ADM ( = CVSD ) is a simple digital implementation, 16kBit i guess. Therefore at 16kBit CVSD is usable, but not for public phone system. Initial circuits were analog: https://get.hidrive.com/5gdAmSyB cvsd-ptarmigan.pdf The CML FX209 is an early integrated analog version: https://get.hidrive.com/HhS2FWU4 cvsd-steele.pdf The Harris HC55564 is a simple digital IC. The CML FX609 is the next and final generation with PCM-like filter that reduces high frequency noise. We did use the Harris. On switching to the FX609 had a test with all the employees in the company with handset what they liked better: 90:10 for the FX609. The problem with "better" is that everyone is accustomed to PCM-filtered speech. All these ICs one can get via ebay.com from China. Using 2 on breadboards one can build a simple channel that "distorts" speech for testing. Reference would be an old PCM-chip. As for quality: the 64kBit PCM may be the gold standard, but the cordless DECT phones use ADPCM at 32kBit with hardly any loss of quality. This is not the original CCITT-ADPCM that was very complex. But i still doubt implementation on an AVR is easy. CVSDs i did years/decades ago on PICs/68HC05. MfG JRD
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Voice compression pozz <pozzugno@gmail.com> - 2025-04-02 18:33 +0200
Re: Voice compression Rafael Deliano <Rafael_Deliano@arcor.de> - 2025-04-02 19:55 +0200
Re: Voice compression pozz <pozzugno@gmail.com> - 2025-04-03 19:53 +0200
Re: Voice compression Rafael Deliano <Rafael_Deliano@arcor.de> - 2025-04-05 11:12 +0200
Re: Voice compression pozz <pozzugno@gmail.com> - 2025-04-07 13:13 +0200
Re: Voice compression Paul Rubin <no.email@nospam.invalid> - 2025-04-04 13:54 -0700
Re: Voice compression pozz <pozzugno@gmail.com> - 2025-04-07 13:09 +0200
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