When dealing with music, I consider myself an audiophile.  When I buy a CD, I rip it to my home server in the FLAC format; No, I don't carry loss less audio around on my portable devices...  But I like AAC when my player supports it, and MP3 when it doesn't.  My primary concern with storing my primary source in either lossy format is that if I convert between the two, it's going to lose MORE data/quality with each conversion...  Lossy on top of lossy is bad.

The same is true of these vocoders...  They are all lossy formats... And at such low band widths, they don't leave much left over to be lost again.  My point is this: A transcoder between any two formats that use different vocoders will significantly degrade the audio quality...  Maybe it will still be legible, but I doubt it will be a pleasant experience. 

In light of that, going from one digital mode to another may or may not be considered worse than going from FM to digital, depending on the real world performance of that double (or potentially triple in a poorly optimized network) lossy conversion.

On Wed, 23 May 2012, Tyrell Berry wrote:

A transcoder between any two formats that use different
vocoders will significantly degrade the audio quality... Maybe it will
still be legible, but I doubt it will be a pleasant experience.

Witness, in order of decreasing quality, conversations from:

*) Analog phone -> analog phone
*) Analog phone -> cell-phone
*) cell-phone -> cell-phone, same technology
*) cell-phone -> cell-phone, different technology

I've had extremely poor conversations with the last mode, with a friend using a different kind of cell-phone technology than my phone.

It's _exactly_ what's being discussed here, conversions from once codec to another. The more conversions in the line, the poorer the quality. Real-world examples that most of us experience on at least a weekly basis.

--
Curt, WE7U. http://www.eskimo.com/~archer
Windows ate my homework!

Tim

If this was professional radio, then I'd agree. But it isn't - it's hobby radio, and the goal is to experiment, not to provide a service-provider grade network.

As a friend of mine recently told a group, if you want high data rates, 100% coverage, 5 9s reliability and black-box equipment, we have 7 main mobile operators and at least two dozen MVNOs that will do that for you. And you can buy their hardware in the supermarket for next-to-nothing !

So I see nothing wrong with linking between modes at any quality in the spirit of "education through experimentation in radio" as my licence says.

If you are in a country that uses Amateur radio to support emergency response, I would have thought that linking at any quality was better than no linking at all.

I'm not sure of the situation in the US, but across much of the EU, voice transmission is rarely used these days by emergency services for routine matters - most dispatch is done by data with a hard copy printed in the vehicle for audit/accuracy purposes. I know that Italy still has individual analogue radio systems for each force/area but is swapping out later this year for a nationwide TETRA network and is one of the last countries to do so. TETRAPol in France is even older then TETRA - their national network went in some 20 years ago. The UK was late to the game, and it wasn't until about 6 years ago that the last isolated users came off their own radio systems onto the national backbone.

I don't see Amateurs building a global TETRA cellular system any time soon.....

David

Sent from my iPhone

A good point! We'll have to see what shakes out as the experimenters "experiment" with linking digital systems.

73 de Tim, AF1G

---- Tyrell Berry <kd7kuj@...> wrote:

=============
When dealing with music, I consider myself an audiophile. When I buy a CD,
I rip it to my home server in the FLAC format; No, I don't carry loss less
audio around on my portable devices... But I like AAC when my player
supports it, and MP3 when it doesn't. My primary concern with storing my
primary source in either lossy format is that if I convert between the two,
it's going to lose MORE data/quality with each conversion... Lossy on top
of lossy is bad.

The same is true of these vocoders... They are all lossy formats... And at
such low band widths, they don't leave much left over to be lost again. My
point is this: A transcoder between any two formats that use different
vocoders will significantly degrade the audio quality... Maybe it will
still be legible, but I doubt it will be a pleasant experience.

In light of that, going from one digital mode to another may or may not be
considered worse than going from FM to digital, depending on the real world
performance of that double (or potentially triple in a poorly optimized
network) lossy conversion.

... doesn't exist.

This forum has been wonderfully active on a variety of topics. It's great to see the exchange as hams weigh in with their hopes and dreams, but there is one topic that I need to address; the notion of open source hardware.

I worked in Silicon Valley for 30 years, both with and for, a variety of semiconductor companies. I have personally negotiated with both ARM and MIPs and let me tell you, there is no open source hardware.

Today's designs use high integration ICs which are designed in HDLs. They often include licensed IP from other sources under highly restrictive agreements. They are the companies most valuable assets and they are not released to anyone in any form.

In order for us to use these devices we may enter into Non Disclosure Agreements which state that we will not release any design information to third parties, that means you. In particular if there are errata we cannot share either the problem or the fix.

LEGAL DISCLAIMER: I am not saying that any vendors chips that I use now, or have ever used, actually have now or ever have had any errata (hi hi).

What we will provide is schematics and assembly diagrams of released product under copyright. In particular, we will document all connector interfaces both external and internal, to aid in experimentation.

We will not be posting manufacturing data, such as gerber files, detailed BOMs and mechanical drawings, but if you have an amateur radio project that requires more information; send us an email briefly describing what you'r trying to do and we'll do our best to help you.

73 - Bryan Hoyer

I would add that there has been a lot of work done looking at tandeming vocoders. Conclusion a noticeable loss in audio quality measured in the mean opinion score. If you could find a way to bridge between the two vocoders that would avoid the existing patents that would be good. So I will stick with D-STAR where I have the most invested. Maybe cross link co-located FM repeaters in a way to set up headers in a meaningful way.

73, tom n4zpt

On 5/23/2012 12:53 PM, Tyrell Berry wrote:

When dealing with music, I consider myself an audiophile. When I buy a
CD, I rip it to my home server in the FLAC format; No, I don't carry
loss less audio around on my portable devices... But I like AAC when my
player supports it, and MP3 when it doesn't. My primary concern with
storing my primary source in either lossy format is that if I convert
between the two, it's going to lose MORE data/quality with each
conversion... Lossy on top of lossy is bad.

The same is true of these vocoders... They are all lossy formats... And
at such low band widths, they don't leave much left over to be lost
again. My point is this: A transcoder between any two formats that use
different vocoders will significantly degrade the audio quality...
Maybe it will still be legible, but I doubt it will be a pleasant
experience.

In light of that, going from one digital mode to another may or may not
be considered worse than going from FM to digital, depending on the real
world performance of that double (or potentially triple in a poorly
optimized network) lossy conversion.

On May 23, 2012 9:32 AM, "Tim Hardy AF1G" <hardyt@...
<mailto:hardyt@...>> wrote:

I'm not opposed to linking different protocols, but there is value
in some of the objections to linking specific networks. If the
objections or concerns can be mitigated, then fewer people would resist.

The most often heard objection to linking FM systems to D-Star seems
to be that D-Star users don't want all the white noise from a weak
FM station digitized and retransmitted on D-Star, and I agree with
this objection. Find a way to limit the retransmission of FM signals
onto the D-Star network to only good, mostly full-quieting signals
and you will probably overcome these objections.

Echolink and IRLP were a match because they both use the same mode, FM.

Linking one type of digital system to another won't have this
specific problem, so I don't see why we couldn't develop this option
as long as protocols in each system are satisfied. For example,
D-Star sends the callsign of the transmitting station through the
network. Make this happen from the non-D-Star system and the D-Star
network would probably be satisfied. Otherwise, there will continue
to be objections.

Tim, AF1G

---- "Tony Langdon wrote:

=============
At 11:51 AM 5/23/2012, you wrote:
>"this is something that should have been done ten years ago"
>
>QFT
>
>Unfortunately it wasn't, and that the biggest issue I have with the
>development of D-Star. Having said that, Amateur Radio is already a
>splintered hobby with many niches, so it's nothing new.

D-STAR was developed a long time ago, technology has moved on since,
also.

>What concerns me more is the (political) resistance to allowing
>interoperability/gateways between systems. The transcoding, gateways
>and transports themselves are all relatively minor feats in
>comparison. All it takes is "someone" saying they won't allow gating
>from IRLP to Echolink, Echolink to D-Star, or P25 to whatever, and a
>segment becomes isolated. We're our own worst enemy and we'll pay
>for it in real dollars.

Agree totally. To me, the ultimate aim is to have a

>I don't want to have to take three HT with me when I leave the
>house, or have a rack of three mobile rigs in the car. I also don't
>want my investment in D-Star to become worthless.

I had the same issue back in 2002, when I was running IRLP and
Echolink on a single antenna, which meant that two of the 3 ports on
my triplexer were taken up with links! As I was the main user, there
had to be a better way. I wasn't the only one who thought this, and
a few people put their heads together and came up with EchoIRLP,
which allowed the same analog endpoint to be used for both
networks. With digital, there's no common medium until you get to
the end user radio itself, so you either need a multiprotocol radio,
or you need infrastructure which can route across networks (and
willing network administrators!). At least with digital, it should
be possible to transparently carry IDs from end to end, leaving only
the need to cross from network to network, and transcoding the audio
where necessary.

If the gateways can be built out of something like the UDR, then that
could push the protocol conversion as close to the edge of the
network as possible, which might scale better, as well as minimising
issues of "We don't want XXX on our network!".

73 de VK3JED / VK3IRL
http://vkradio.com

&#92;

A few years back, there was an organization that developed two open source phone called the Openmoko Neo and Freerunner.  The devices were nearly entirely open source...  Everything but the GSM Radio, which they claimed couldn't be avoided due to FCC type approval, which is probably true.  But the device in it's entirety, down to engineering drawings of the boards and cad drawings of the case were available for download from openmoko.org. 

Of course, sacrifices were made...  to get around NDAs they had to use fairly archaic chips, even for the time...  As such, the device sold very poorly, and I wouldn't advise following in those footsteps, but to say it doesn't exist is a bit rash.

At 02:47 AM 5/24/2012, you wrote:

So the main benefit of TDMA is being able to double repeater capacity in one RF slot. That's one antenna, one duplexer, one site rental. Certainly in the UK where we pay commercial rates for tower access and there is no free spectrum, it's a big deal.

True, useful in densely populated areas. Out where I am, where there's fewer repeaters and bigger distances, I'm concerned about the cost of that increased capacity - namely the effect on range, caused by timing limitations (AKA physics - the speed of light!).

73 de VK3JED / VK3IRL
http://vkradio.com

At 11:02 PM 5/23/2012, you wrote:

I'm not opposed to linking different protocols, but there is value in some of the objections to linking specific networks. If the objections or concerns can be mitigated, then fewer people would resist.

The most often heard objection to linking FM systems to D-Star seems to be that D-Star users don't want all the white noise from a weak FM station digitized and retransmitted on D-Star, and I agree with this objection. Find a way to limit the retransmission of FM signals onto the D-Star network to only good, mostly full-quieting signals and you will probably overcome these objections.

Actually, there is a way, but it requires some money thrown at the problem. I have a German built DSP that is incredibly effectively at removing FM background noise. Maybe something to experiment with at some stage.

Echolink and IRLP were a match because they both use the same mode, FM.

Linking one type of digital system to another won't have this specific problem, so I don't see why we couldn't develop this option as long as protocols in each system are satisfied. For example, D-Star sends the callsign of the transmitting station through the network. Make this happen from the non-D-Star system and the D-Star network would probably be satisfied. Otherwise, there will continue to be objections.

Being digital all round, that shouldn't be too difficult, though it might need some lookup tables for systems which don't use the callsign as a MAC address. I believe TRBO uses a numeric ID, for instance.

73 de VK3JED / VK3IRL
http://vkradio.com

At 02:53 AM 5/24/2012, Tyrell Berry wrote:

The same is true of these vocoders... They are all lossy formats... And at such low band widths, they don't leave much left over to be lost again. My point is this: A transcoder between any two formats that use different vocoders will significantly degrade the audio quality... Maybe it will still be legible, but I doubt it will be a pleasant experience.

In light of that, going from one digital mode to another may or may not be considered worse than going from FM to digital, depending on the real world performance of that double (or potentially triple in a poorly optimized network) lossy conversion.

Another reason to push the network translation to the edge of the network, and another reason why EchoIRLP was better than other cross network solutions at the time. If you have multi protocol capable gateways, they will could attempt to choose a path that limits the number of transcoding operations to the ideal (0 between networks which use the same vocoder - EchoIRLP achieved this, or 1 when there was no vocoder in common).

73 de VK3JED / VK3IRL
http://vkradio.com

At 03:14 AM 5/24/2012, Curt, WE7U wrote:

Witness, in order of decreasing quality, conversations from:

*) Analog phone -> analog phone
*) Analog phone -> cell-phone
*) cell-phone -> cell-phone, same technology
*) cell-phone -> cell-phone, different technology

I've had extremely poor conversations with the last mode, with a friend using a different kind of cell-phone technology than my phone.

It's _exactly_ what's being discussed here, conversions from once
codec to another. The more conversions in the line, the poorer the quality. Real-world examples that most of us experience on at least a weekly basis.

Which is a good reason to be clever about how we do things. :) I'm a believer in fiddling with the signal as little as possible, for this very reason.

73 de VK3JED / VK3IRL
http://vkradio.com

The argument that analog should never be linked to digital because of white noise and other artifacts forgets that Vocoders (as opposed to Codecs) like AMBE and Codec-2 are specifically looking for speech and work hard to remove background noise.  All audio starts and ends as analog and transitioning from an analog FM to digital voice system using a vocoder applies the same filtering to the audio.  I think the folks the argument haven't tested their theory.   Some who have tested it, can probably show some issues like drop out, overdrive on CTCSS, etc. that will degrade the system, however, well conditioned audio from an analog FM source should encode much like analog voice from a microphone.

John,

I think as long as the proper display is there, someone using the 1.2k gmsk modem with analog audio (or echolink with callsign pass-through) won't really be noticed. It will probably require some special tricks somewhere along the line to properly work with the Icom gateway software and such, but that's already taken care of in Jomathan's software.

Matthew Pitts
N8OHU


------------------------------

Matthew,

The entire “MY” call is unenforceable. It is sent in clear text, is programmed by the user and therefore is suspicious.



By default, my code does not check D-Star MY calls for one simple reason – it could land me in gaol.


In most of the EU, it would be illegal for me acting as a citizen to deny another citizen access to systems designed for the whole community based on my perception of their licensed status. If it turned out that the other party WAS licensed and I had denied them access, then I would have committed a very serious offence in both anti-discrimination and Human Rights terms. That is a custodial sentence.



The only people with the power to investigate illegal transmissions are the police (or Ofcom working with the police) and the public is advised to stay out of police business. As any form of closed system is also not allowed, that means that irrespective of what someone TELLS me either verbally or by electronic ID, I cannot afford to block them for fear of acting illegally. If they break the rules of their licence, it is not for me to say other than reporting my suspicions to the authorities.



So, callsign ID on D-Star is pretty meaningless !



David

At 09:02 AM 5/24/2012, you wrote:

Any linking protocol that mixes systems should contain an ability to identify the type of traffic source (Analog, Digital) and encoding (AMBE, Codec-2, etc.) and allow the administrator of a repeater to determine which traffic to accept.

A key issue identified many years ago is that control over what sort of traffic should be allowed to pass through a gateway should be in hands of the administrator of that particular gateway/repeater. If I want to allow transmissions of analog origin on my repeater, I should be allowed to simply enable reception of that type of traffic. And if I don't want it (there are legal reasons for not allowing _some_ analog systems to link to digital here), then I should be able to block it.

Similarly, I should not be able to "force" unwanted traffic types on another gateway.

Given these two "non-issues", the rest is just politics. :)

My sentiments exactly. :)

73 de VK3JED / VK3IRL
http://vkradio.com

At 11:18 AM 5/24/2012, you wrote:

All the time we have the entrenched view of
“this is my system and it won’t connect to
your system� we risk siloing and isolating
users. The net effect is less usage on amateur
bands and less amateurs – exactly the effect
that is being seen in many countries.

At the end of the day, all that the majority of
people want to be able to do is talk to their
friends around the world, and not have to jump
through political hoops to do so.

On the callsign ID, that is an interesting
point. Rules do vary from country to country,
but what I’ve found is that Amateurs naturally
ID every few minutes anyway. In the UK, rules
were relaxed on D-Star so that no voice ID is
required, but you will still typically here an
over start with “G6TBA from G4ULF� and end
with “from G4ULF.� Old habits die hard,
and I certainly ID on every over still.

Similar observations in Australia. However, for
us, this was always a non-issue, because
transmitter ID, not origin ID is the critical factor.

So, again, like you, I think these are both non-issues.

To me, the benefits in terms of increase usage
and more linking possibilities far outweigh these issues.Â

BTW, EchoIRLP does NOT allow interworking IRLP
and Echolink as the IRLP crowd insist on the
end-point being a repeater.   EchoIRLP
allows a repeater to act as an IRLP node and and
Echolink node, but it does not bridge the audio together.

This was one of the original design decisions,
though strictly speaking, there is a bridge
between the two at the protocol level, but it
takes place in the EchoIRLP node when running
Echolink. A copy of thebridge does act as a
local protocol translator between Echolink and
IRLP/Speak Freely (some control functions and
audio transport layer), so the IRLP software can
remain in control of the audio path, as well as
provide sensible status reports to both networks as needed.

73 de VK3JED / VK3IRL
http://vkradio.com