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M17-Project / M17_spec

M17 standard specification
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lyra V2 3200bps codec support #119

Closed philipag closed 1 year ago

philipag commented 1 year ago

The Lyra v2 codec supports 20ms 3200bps frames just like codec 2 so it would be a drop-in codec 2 replacement for that mode. A cursory look indicates that lyra V2 audio quality is considerably higher than codec 2 at this bit rate. Also the source code is c++ so easy to integrate with M17.

It's just a thought but this would put audio quality far above what DMR and the other protocols provide - the type of advantage that could propel M17 into the mainstream.

sp5wwp commented 1 year ago

Have you tried coding speech with Lyra in realtime on an MD380-class handheld?

philipag commented 1 year ago

No but V2 of the codec is fairly efficient and may well be possible on the 100-400 MHz arm cores we see in radios today.

Of course this is something that needs to be evaluated.

sp5wwp commented 1 year ago

Interesting. Try it out and tell us if it's feasible.

philipag commented 1 year ago

I don't have a radio to test this on. I won't be able to work on this now - just wanted to mention it as an interesting option.

In the future I may evaluate this for another unrelated project and will report back if I do.

philipag commented 1 year ago

Lyra V2 appears to run about 35x realtime on a modern phone core so my guess is that a 400Mhz Arm7 core will easily be fast enough. The STM32F405VG @ 168MHz would probably also be able to handle it but that would require testing.

Some useful information on embedded Lyra V1 which is much slower: https://stackoverflow.com/questions/71415999/google-lyra-on-bare-metal-microcontroller

kc1awv commented 1 year ago

Moving this to Discussions, as it's not really an issue.