I went hogwild with this at the beginning of the RTLSDR era of SDR. I just started picking it back up after getting some better hardware and was kind of bummed at how little the quality of the voice decoding has progressed despite what appears to be a ton of energy invested.
If I recall correctly some of it is licensed and/or patented and people are just having to reverse engineer the protocols. I’d pay for a commercial demodulator to snap in.
You can buy the DVSI codec wrapped up in a USB stick from NW Digital Radio. They call it the "ThumbDV". It looks like a serial port to your machine, and you can just poke it with the right commands and it'll turn raw codec data into raw audio data (and vice-versa).
I used it for decoding the AMBE+2 stuff on newer P25 systems. It wasn't great but it did mean I didn't run afoul of any patent issues if I wanted to sell the system to someone else. OP25 is great but I didn't want to take the risk.
Whoa, interesting, thanks for the heads up! I've bookmarked that puppy.
Whatever I was watching recently still had that slurring effect in all of the speech that I recall from back in the day, but I just checked out some recent recordings from OP25 and that is actually quite a bit improved. May just try that out first and see where it goes. Thanks!
If I recall correctly some of it is licensed and/or patented and people are just having to reverse engineer the protocols. I’d pay for a commercial demodulator to snap in.