Seeking someone to improve D-Star Open-AMBE

Discussion in 'Ham Radio Discussions' started by KB9MWR, Sep 3, 2020.

ad: L-HROutlet
ad: l-rl
ad: Subscribe
ad: L-MFJ
ad: Left-3
ad: Left-2
ad: abrind-2
  1. KB9MWR

    KB9MWR Ham Member QRZ Page

    Overview:
    The AMBE speech coder problem started when D-Star was developed and introduced to ham radio in the late 90's early 2000's. It's since been compounded by DMR, Yaesu Fusion, and other digital HT's. The propose solution has been to replace this with an open source codec. However, none of these digital modes have a means to specify or differentiate the audio codec should they ever want to move away from AMBE. And there still isn't much of working implementation of Codec2 for VHF/UHF radios. There is a working implementation for HF. Codec2/FreeDV is a good conception, but it hasn't come to fruition in the advent of the AMBE patents expiring and other digital radios also employing AMBE and flooding the market.

    For many hams these days the AMBE concern is not well understood. First you have to take a larger look at the point of amateur radio. To learn about radio, propagation, and the electromagnetic spectrum in general. To understand how it works, and maybe even build or modify your own equipment. In order to learn we must be able to inspect; to tinker, or at the very least have access to a specification we can build from.

    So while D-Star was interesting as it was a new thing to play and learn about when it came about, there was this "black box" aspect where you just buy and are a passive consumer. This didn't sit well with many. Why even bother with a hobby of sharing and learning, if theres a big wall saying this far, no further!, that you are not permitted to create your own radio for. Or permitted to understand.

    The "HT of the Future" talk that Bruce Perens also gave some time ago, did also stress the need to have open radio firmware. Lets take a quick look at why this would be good for the hobby.

    The Linksys WRT54G WiFi router of the early 2000's was a good example of the good that can come from open firmware/open source. The history here was the original factory firmware was discovered to be based on Linux components, which are covered by the GPL. This required the manufacture to release the source code. With the code in hand, developers learned exactly how to talk to the hardware inside and how to code any features the hardware could support. It has spawning a handful of open source firmware projects for the WRT54G that extend its capabilities, and reliability, far beyond what is expected from a cheap consumer grade router. In short due to open source, one can load a third party firmware on the router and give a $60 consumer home-grade router into a all the functionality of a $600 Cisco professional router.

    While there have been a few radio firmware reverse engineering efforts. The most well know was the MD380 project by Travis, KK4VCZ. The hobby can use a lot more of this and a lot more people like Travis. We haven't yet figured out how to re-write a radio's firmware to create that elusive digital radio that that can do more than one digital mode. But that day may still come. Software Defined Radio was likely a foreign concept to many 20 plus years ago when this problem was first brought to our awareness by Bruce Perens. USRP, HackRF, HamShield, RTL-SDR, are know to many now, and having to have a hardware dongle to do the speech coding with those is illogical.

    The Need:
    At this point, while the AMBE used in D-Star is out of patent. Since there was never a published specification for it like its other variants, hams have this far not been able to create a software version with similar performance. (Good sounding software AMBE does exist for other modes)

    Software AMBE is extremely handy for folks running cloud based conference bridges like DV Switch, that allow hams to cross communicate between digital modes. It also can be used for internet connected apps that connect to the RF gateways without need for hardware (MMDVM hotspots & HT's).

    The original reverse engineering thread:
    https://forums.radioreference.com/threads/decoding-d-star-any-success.215282/

    Its been said elsewhere that the suspected key to getting it better output is with the quantization tables:
    // decode V/UV parameters
    // load b1 from ambe_d
    //TODO: use correct table (i.e. 0x0000 0x0005 0x0050 0x0055 etc)

    This likely can't happen at the very least unless the coefficients for encoding the specific D-Star variant of AMBE are exposed in a software implementation somewhere like the one in the MD380 firmware. The good news is it appears our good friend Travis has begun working on that.

    In an ideal situation, the D-Star spec would have required publication of this like the APCO specification did. After the fact, I don't foresee any reason for the patent holder to release such details. Another ideal scenario is if the FCC rules actually emphasized or required digital transparency, then not only would this enable those who want to learn and code/build, it would likely force working source code for AMBE to be published tomorrow.

    It seems sad that various national amateur radio organizations have not stepped up to support open source efforts.
    _________________________________________________________________

    For Developers:

    https://github.com/nostar/dudestar
    https://github.com/f4exb/dsdcc - dsd rewrite - C++ library with a single decoder object
    https://github.com/LX3JL/xlxd
    https://github.com/szechyjs/dsd
    https://github.com/szechyjs/mbelib
    https://github.com/LouisErigHerve/dsd
    http://git.osmocom.org/op25/tree/op25/gr-op25_repeater/lib - Op25 has encode and decode support for AMBE (D-Star, DMR and YSF) and IMBE (P25)
    https://github.com/balint256/op25/tree/master/op25/gr-op25_repeater/lib/imbe_vocoder - Pavel's IMBE Encoder/Decoder Fixed-Point implementation
    http://git.osmocom.org/osmo-gmr/tree/src/codec
    https://github.com/on1arf/voice-ann[19]
    https://github.com/dl1bff/ircDDB-mheard/blob/master/ircDDB-mheard.c-Line 383 - handles the bit interleaving and FEC processing
    https://github.com/travisgoodspeed/md380tools/ - The MD380 Emulator (capable of AMBE encoding and decoding)
    https://github.com/g4klx/AMBETools
     
    Last edited: Sep 3, 2020
    K0IDT, K5TRP, N0KEW and 2 others like this.
  2. KB9MWR

    KB9MWR Ham Member QRZ Page

    Doug, AD8DP just finished writing Dude Star. This is a way to retro fit an analog rig so that you can transmit and receive D-Star, DMR, P25, and Yaesu Fusion:

    http://www.dudetronics.com/index.php/dude-star-radio-project

    The catch is, one has to use a hardware AMBE device for D-Star (for now) since the working model for doing that voice coding is marginal.

    Please give Doug's work a try and send him a thanks if you appreciate his work. Doug is one step ahead of the commercial manufactures in terms of hardware that can support multiple digital formats.
     
    KC9ONY and K5TRP like this.
  3. K0RGR

    K0RGR Premium Subscriber QRZ Page

    The Dudetronics solution looks like a winner in the multimode race. Sadly, it can't do level 2 DMR, and it's unlikely that the approach of using an analog radio will ever have that capability as it requires rapid switching of T/R functions to allow time slicing. This is really quite a breakthrough, though, and I would be happy to have the Dstar and YSF functions in a single radio - those seem to be the more active modes, anyway.

    I was at a conference where various promoters of vaporware promised to set themselves on fire if their wares did not appear in reality by the following conference. I believe Bruce Perens said he would set his assistant on fire. I have not seen any flaming developers yet. But Dudetronics seems to be reaching a big milestone.
     
  4. KB9MWR

    KB9MWR Ham Member QRZ Page

    I agree on the DMR part, but if more capable hardware comes along (like if some manufacture ever takes the hint), it will be trivial to add that support. Yes, this is a huge step forward. Finding someone to work on the D-Star AMBE is still on my wish list to compliment Doug's great work. I have my eye on another radio reverse engineering project that Travis Goodspeed's, (KK4VCZ) promoted, this time a Kenwood D-Star radio. This might solve that.

    It's still important to somehow drive home the concept to manufacturer that we'd like to see something like this put into production. So if you see reps from "the big three" at hamfests, tell them to get of their high horse, because the digital fragmentation they continue to promote by only supporting their flavor of digital, is NOT COOL.
     
  5. KA9JLM

    KA9JLM Ham Member QRZ Page

    More people need to Click "Donate to help development of this project"

    That would help to get good coders working on the project.

    You should pay if you play, At least buy the coder a cup of coffee. ;)


    Give credit where credit is due...
     
  6. KB9MWR

    KB9MWR Ham Member QRZ Page

    Where is that Donate link?

    It would be a good idea for Doug to add such a link to his page, but currently I don't see one.

    One could always nominate him here:
    https://amateurradiosoftwareaward.github.io/

    The ideal thing would be for a leading organization such as the ARRL, to have a splash in their magazine about this to recognize his efforts.

    The traditional hardware experimentations that Ham Radio Magazine and 73 Magazine fostered by giving these folks a platform, has changed. There’s ample experimentation and building still going on, it’s just now on a different plane. Nightly builds of new software. Open source software communities. Hacking something built for another purpose. Pinch me when the ARRL starts to recognize this.
     
  7. NK8I

    NK8I Ham Member QRZ Page

    Doesn't the Openspot3 offer crossmoding via hardware?

    What are your thoughts on the M17 project?
     
    Last edited: Oct 18, 2020
  8. K0UO

    K0UO Platinum Subscriber Platinum Subscriber QRZ Page

    Easy fix
    just use DMR!
     
  9. KB9MWR

    KB9MWR Ham Member QRZ Page

    I like the M17 project, but please pinch me when some some manufacturer steps forward to put this into production. So till then, I like things that can interoperate with what we have.
     
  10. NK8I

    NK8I Ham Member QRZ Page

    OK, thanks, and whether the Openspot 3 with the AMBE chip at least will bridge the gap until that ever comes to fruition? I'm on the verge of ordering one...sorry for the derail.

    I'm a relative noob to DMR and cross moding, only have been doing Fusion and D-star the last year, currently no D-Star radio currently but miss the mode..
     

Share This Page