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D-STAR decoder with new version of MultiPSK

ka3jjz

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Some of you may be familiar with the multi mode decoder package known as MultiPSK. It's very popular with the HF decoding crowd (if you can get past all those buttons!) A new version has just been announced that includes a D-STAR decoder (you need to use a discriminator tapped radio or a SDR for this). The announcement has been repeated on several places, but here's one - and I will warn you that Patrick's English is a little rough in spots...


Mike
 

k7ng

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I saw Patrick's announcement a few days ago, and after reading it carefully - yes, the English isn't perfect, but orders of magnitude better than my French... I think I understood that the Multipsk D-star decoder will print out the NON-VOICE data carried on each D-star transmission, or everything when the DV Data feature is in use. Please correct that if I misunderstood. Patrick mentions not wanting to decode voice due to legalities related to AMBE. I think it is possible to decode D-Star Voice without violating DVSI's copyrights but as a Multipsk user for a long time, I figure Patrick knows what he's doing and if he decides to handle voice decoding later on, he will do so.
 

kb9mwr

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I saw Patrick's announcement a few days ago, and after reading it carefully - yes, the English isn't perfect, but orders of magnitude better than my French... I think I understood that the Multipsk D-star decoder will print out the NON-VOICE data carried on each D-star transmission, or everything when the DV Data feature is in use. Please correct that if I misunderstood. Patrick mentions not wanting to decode voice due to legalities related to AMBE. I think it is possible to decode D-Star Voice without violating DVSI's copyrights but as a Multipsk user for a long time, I figure Patrick knows what he's doing and if he decides to handle voice decoding later on, he will do so.
AMBE for D-Star is expired:
 

slicerwizard

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In that video, 38 minutes in, the graphic states that D-Star uses 4800 bits per second for audio and an additional 4800 bits per second for data. Meanwhile, every D-Star transmission that I've ever seen uses a total of 4800 bits per second with 75% of them (3600 bits) used for audio and the remaining 25% (1200 bits) used for routing/text/GPS data.
 

kb9mwr

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Yeah somehow I didn't catch that the first time around. Yeah I have always been told; 2400 for AMBE + 1200 FEC, and then 1200 is for data/gps/text etc = 4800 total.
 

slicerwizard

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Also, the main thing in that talk is that all ham radio manufacturers are using DVSI audio codecs, while Bruce would prefer that they use a free and open codec like Codec2, among other issues. I suspect that manufacturers stick with DVSI because they get an MBE chip that does most of the heavy lifting and it comes with a guarantee that DVSI won't sue them. The alternative is getting a custom chip made or using a beefier microprocessor to do all the work, plus have DVSI threaten to sue them over their use of an open codec; we all know how expensive defending even a baseless lawsuit can be, so here we are...
 

kb9mwr

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Last I checked Codec2 really isn't really compatible with FM. I was interested in using a raspberry pi in conjunction with mobile radio and interfacing it via the packet radio port (discriminator). It would work with a VHF SSB radio though from what I read at the time

As I understand it, codec2/freedv is supposed to be free from all intellectual property issues. So I don't think that is why manufacturers aren't using it. The real issue I think is that is a niche ham radio thing. At his point it doesn't make sense to me for VHF/UHF anyway. There are to many flavors of digital already. I cringe at the thought of yet another. Makes sense for HF though, where bandwidth is more scarce and you are already pretty much used to listening to donald duck.

While I am glad Bruce trys to inform the community on the legal status of things, I'd be more appreciative if he'd give a more technical talk on the nuts and bolts of say improving the open D-Star AMBE to sound a little better.
 

slicerwizard

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Last I checked Codec2 really isn't really compatible with FM. I was interested in using a raspberry pi in conjunction with mobile radio and interfacing it via the packet radio port (discriminator). It would work with a VHF SSB radio though from what I read at the time
I don't see why it would be incompatible with FM. All codecs reduce speech/audio to ones and zeroes and FM has no problem carrying digital data.

As I understand it, codec2/freedv is supposed to be free from all intellectual property issues. So I don't think that is why manufacturers aren't using it.
That wouldn't stop a lawsuit.

The real issue I think is that is a niche ham radio thing. At his point it doesn't make sense to me for VHF/UHF anyway. There are to many flavors of digital already. I cringe at the thought of yet another. Makes sense for HF though, where bandwidth is more scarce and you are already pretty much used to listening to donald duck.
It could be added to radios and repeaters to provide a common format. But that is something that manufacturers are not interested in doing.

While I am glad Bruce trys to inform the community on the legal status of things, I'd be more appreciative if he'd give a more technical talk on the nuts and bolts of say improving the open D-Star AMBE to sound a little better.
It could be improved by supporting an alternate, better, codec. Signaling bits could be used to negotiate which codec should be used. Legacy gear would ignore the negotiation and comms would fall back to AMBE. Not particularly complicated.
 

kb9mwr

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The incompatibility that I was recalling was with FreeDV 2400A as it requires a SDR with a 5kHz RF bandwidth. Basically as I understood it to achieve better readability, the current crop of radios (FM) weren't going to make that happen.




However I just stumbled into this:

"Collection of Python code to experiment with D-STAR and the proposed vocoder extension that allows the use of the open source Codec 2 with D-STAR"


Which at this point in the game really only makes sense to me if someone is going to start hacking a D-Star radio, in the same manner that was done with the MD-380. Else I don't really get it.
 
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