[Linux-ham] Opus over 9600 baud KISS TNC

[Tadd Torborg]

Kevin,
  This sounds really hopeful.  Are you still working on the idea that latency is not permitted?  Or are you allowing latency? 
  I would really like to see this working across G8BPQ nodes.  If the system used G8BPQ on both ends, we could use SLIP or twisted pair over-audio and take the radios out of the test.  I would come up with test radios and digital hardware if this would help.  I could do desktop PCs or Raspberry PIs.  I can loan DRSI/Kantronics 9600 baud data radios (2 ends)  as well as TNC-PI 1200 baud devices.  
  You and I are almost in network range with the TARPN system.  I'm putting up a 3-port node in the next two weeks weather permitting at NC86 x i-40. 
    Tadd / KA2DEW - Raleigh NC

http://tarpn.net      Terrestrial Amateur Radio Packet Network
tadd at mac.com

On Dec 30, 2014, at 12:44 PM, Kevin Otte <nivex at nivex.net> wrote:

> I migrated the code from my personal SVN over to GitHub to make
> interaction easier. I also made some headway trying to do text encoding
> of codec2. Full rundown with github links:
> https://groups.google.com/forum/#!topic/digitalvoice/vqJ-HnER2lU
>
> On 08/24/2014 02:38 PM, Kevin Otte wrote:
>> tl;dr:
>> - Code is at http://www.nivex.net/svn/dvopus/
>>  
>> - I think I've got some buffering problems.
>> So, I had a crazy idea: send low bitrate (I chose 7.2Kbps based on what
>> other protocols are using for "high bitrate" to leave room for headers,
>> etc.) Opus data using 9600 baud KISS TNCs. I have a Kenwood TH-D7Ag and
>> a TM-D700A, both of which have those in it. Piece of cake, right?
>> Well, getting the encoding and the KISS framing coded up took some time,
>> but it was all pretty doable. Piping the output of the transmit program
>> to the receive program via an mkfifo works just fine (with headphones!
>> The delay is low enough to create feedback). Hooking it up to the
>> radios, notsomuch.
>> First I tried sending from the D7 to the D700. My ears heard data, but
>> the D700 never returned any frames. I flipped things around and data
>> started flowing, but it didn't stay that way for long.
>> The transmitter would burst a few frames, then unkey, and start again.
>> The txdelay is 200ms, so that was killing any real throughput. I imagine
>> the computer would be more than capable of keeping the buffer full so it
>> wouldn't have to unkey, so I wonder if I have the other problem. That
>> is, I'm swamping the buffer in the radio. These things were only ever
>> designed to send APRS frames, and KISS mode isn't even in the manuals.
>> Eventually I overran a receive buffer somewhere (probably missed a frame
>> separator) and tripped a failsafe in the code.
>> So, I have a prototype, but it doesn't really work. A partially blinking
>> "Hello World" LED is still an improvement over a doodle on the back of a
>> napkin, but this still might not be viable.
>> Some ideas for improving matters:
>> - Increase the bitrate, maybe 8Kbps
>> - Adjust the frame size. not sure whether to go up or down. Up (60ms)
>> would reduce the per-frame overhead but increase the latency. This might
>> help the buffering issue too.
>> Anyway, that's what I've been messing around with lately.
>> 73 de Kevin N8VNR
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