Supporting DVSI chips / legal aspects

[mweyland]

It is not quite clear under what circumstances and in what parts of the world it is OK to use mbelib. Maybe there is need to support the actual DVSI products instead of using mbelib...

This probably involves legal insights from people who are not me. Preferably insights that are not restricted to the US, if possible.

[n8ohu]

I suspect that using it is legal insofar as you're not using it to develop a commercial product that uses the AMBE Vocoder. However, supporting the hardware that exists to process it is a wise decision.

[mweyland]

This is the permutation needed to convert a 49-bit AMBE frame in DN-mode to something the DVSI chip can understand:

0 3 6 9 12 15 18 21 24 27 30 33 36 39 41 43 45 47
1 4 7 10 13 16 19 22 25 28 31 34 37 40 42 44 46 48
2 5 8 11 14 17 20 23 26 29 32 35 38

[f4exb]

Is there a similar permutation for the 88 bit IMBE frame in VW-mode? The DVSI chip does not directly understand either the 88 bit sequence that mbelib decodes. I am using the AMBE3000 chip in 4400 bps rate with no FEC

[mweyland]

Hello. To the best of my knowledge, you cannot use the AMBE-3000 for VW mode. This is because they are using a rate that is simply not supported by the chip, see also issue #13. I think your best chance is to do it in software. Note that the osmocom op25 project has an IMBE de- and encoder which would probably work for this.

If your goal is to just apply FEC and retransmit the packet (e.g. in a repeater), you can simply do that without the need of the DVSI chip at all. Does that answer your questions?

[f4exb]

Hello. Thanks for the information and mentioning the op25 project (useful when I will work on the encoding part). I'll stick with the software version and mention it as a limitation. So yes this answer the question thanks!