Opulent Voice is an open source high bitrate digital voice (and data) protocol. It’s what we are using for our native digital uplink protocol for ORI’s transponder project. Opulent Voice is also looking pretty darn good for terrestrial.
Here is an audible example of the Opulent Voice audio quality under ideal conditions. Each file is about 37 seconds long. It starts with a short musical intro, and the rest is the beginning of the audio track from one of Michelle’s conference talks. These were originally recorded with mid-range podcasting studio gear. The recording was converted to a signed 16-bit PCM raw file, which has been re-converted to a standard WAV file so you can play it easily, MDT-short.wav
This file was then run through opv-mod to create a file of baseband samples, which was then piped to opv-demod, which created an output file of signed 16-bit PCM. That file was converted to WAV file MDT-short.demod.wav
We expect to present a nice demo at DEFCON in August 2022 and at the QSO Today Ham Expo in September 2022.
We’ll be using COBS protocol within Opulent Voice. If you’re unfamiliar with COBS, please read about it here:
https://en.wikipedia.org/wiki/Consistent_Overhead_Byte_Stuffing
Authentication and authorization is built in and optional. There is no separate “packet mode”. Things are designed to “just work” and get out of your way whether or not you’re sending voice or data.
Opulent Voice is designed to where you can use even higher bitrate OPUS codecs if you wish. This will most likely be a build option and not a run-time option, but if a run-time option is something you want to work on, speak up! Let’s see what we can accomplish.
Originally based on Mobilinkd codebase that implements M17, the Opulent Voice development implementation can be found here:
https://github.com/phase4ground/opv-cxx-demod
Initial demos will be on a HackRF/PortaPack on the 1.2 GHz ham bands.
Thank you to OpenRTX for help with troubleshooting the audio quality on the PortaPack. In order to have a good demo, basic FM transmit from the microphone needs to work. The audio quality is pretty bad (this was a surprise) with the stock application, so we’ve been spending some time with the Mayhem codebase, the microphone transmit app, and the driver for the audio codec in order to get it sounding like it should. This needs to happen before we publish an app for the PortaPack.
Synthesized audio from the HackRF/PortaPack sounds clear and wonderful. It’s just the microphone that is splattery and overdriven.
ORI’s Slack channel can be found at https://phase4ground.slack.com/
The authentication and authorization work is in #aaaaa
Opulent Voice work is in #opulent-voice
Thank you to everyone supporting the work!
-Michelle Thompson
Is there a reference implementation for using Opulent Voice on, for example, a Raspberry Pi, audio interface, and a radio with a flat audio connection?
The earlier 4-ary FSK implementation of Opulent Voice flew on UPR’s RockSat-X in August 2024 and the code can be found here: https://github.com/OpenResearchInstitute/opv-cxx-demod
We evolved this design to Minimum Shift Keying (MSK) and targeted the PLUTO SDR. It’s slated for another RockSat-X in 2025, other SDRs, an ASIC tapeout, terrestrial deployment, and is the native digital uplink for our GEO/HEO open source satellite Haifuraiya.
A general purpose processor version (MSK) would start development no earlier than mid-2025.
And, I asked the Opulent Voice team about this at the regular weekly meeting. Here’s the jump: https://youtu.be/_MAg72cwpN8?si=mQWO_rjg_HL5oQ7D&t=1483
-Michelle Thompson