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Codec2


Tom Azlin N4ZPT <tom@...>
 

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;


"Tony Langdon, VK3JED" <vk3jed@...>
 

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


"Tony Langdon, VK3JED" <vk3jed@...>
 

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


"Tony Langdon, VK3JED" <vk3jed@...>
 

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


"Tony Langdon, VK3JED" <vk3jed@...>
 

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