Topics

Bridging the digital voice and data gap

Matthew Pitts <daywalker_blade_2004@...>
 

Tyrell,

The transcoding between AMBE and Codec2 has been done by Kristoff ON1ARF; his blog has some sound samples that I have listened to. I will admit that they may not be the neat sounding speech with multiple conversions, but it's still a lot clearer than analog signals from a fringe area into an analog repeater.

As an update, it appears that AMBE to AMBE should be fairly easy, especially between D-Star and NXDN; there appears to be only a difference of 50 Hertz in the sampling rates, and a similar difference in the error correction. I will have to research the difference between D-Star and DMR next.

Matthew Pitts
N8OHU


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From: Tyrell Berry ;
To: Subject: Re: [UniversalDigitalRadio] Re: Bridging the digital voice and data gap
Sent: Fri, Aug 3, 2012 2:00:31 PM

 

Again, I'm not an audio engineer, and I have been wrong before...  but isn't saying that the chip is a vocoder and it is not compression kind of like saying MP3 is a Muscoder and is also not compression? Is it somehow true that because someone chooses to use a different vocabulary that the principles of which I speak somehow cease to apply?

It has been said several times before, and I will agree: it's entirely possible that transcoding through back to back vocoders may produce legible audio...  Only one way to find out, and I look forward to hearing recordings of the results.  

On Aug 3, 2012 6:51 AM, "Bryan Hoyer" <bhhoyer@...> wrote:
 

The UDR56K has an expansion interface which is designed for an optional ambe vocoder (it is NOTcompression).

DVSI chips are TI DSPs that are factory programmed with their code. The interface is 2 SSPs or synchronous serial port which connect directly to the Marvell SOC.

The interface and drivers wil be documented.

Bryan

"John D. Hays" <john@...>
 

Hi Tyrell,

Vocoders and other codecs are different beasts.  

Two short articles:

http://en.wikipedia.org/wiki/Codec

In layman's terms, a codec converts an analog stream into a coding format.  Some coding formats are lossless and produce a true representation of the orignal analog stream in a digital format, but most such as MP4 and AAC, use compression to get a lower data rate.

A vocoder is considered a type of codec, in that it is converting "analog" voice to what is usually a very low data rate bitstream and back.  However, it's methodology is fundamentally different than traditional audio lossy and lossless codecs.  AMBE and CODEC2 both approach the problem by detecting and recognizing phonemes (the basic sounds that make up human speech) and such things as frequency slope, amplitude, and inflection in the analog stream.  The vocoder then represents the phonemes and modifiers as digital codes (e.g. 0x3E might represent the 'th' sound), which are transmitted digitally, where the receiving end uses those codes to synthesize the original speech.  This process is focused on human speech and has the side effect of mostly ignoring sounds that are not human speech.

The semantic is important to differentiate both the technique and result of the method of encoding and decoding speech.  If you transcoded an MP3 (lossy) music stream into AMBE or Codec2 the result would likely be unrecognizable.  

It may be that transcoding between two similar vocoders would exhibit less deterioration of a voice signal, since they would both be looking for the same attributes in the "audio" signal.  We won't really know until someone tries it in the real world.

Everything else on the "data" side of a complex DV radio protocol can probably be handled, in one form or another, though there would be mismatches.  For example, going from D-STAR to DMR, "callsign addresses" and unit identifiers could be mapped to one another.  On the other hand, there is no equivalent to D-STAR's ancillary data (e.g. comment text, D-PRS, etc.) in IRLP's network, though a SIP link could send it as a message in the control channel.


John D. Hays
K7VE
PO Box 1223, Edmonds, WA 98020-1223 
  



On Fri, Aug 3, 2012 at 7:00 AM, Tyrell Berry <kd7kuj@...> wrote:
 

Again, I'm not an audio engineer, and I have been wrong before...  but isn't saying that the chip is a vocoder and it is not compression kind of like saying MP3 is a Muscoder and is also not compression? Is it somehow true that because someone chooses to use a different vocabulary that the principles of which I speak somehow cease to apply?

It has been said several times before, and I will agree: it's entirely possible that transcoding through back to back vocoders may produce legible audio...  Only one way to find out, and I look forward to hearing recordings of the results.  

On Aug 3, 2012 6:51 AM, "Bryan Hoyer" <bhhoyer@...> wrote:
 

The UDR56K has an expansion interface which is designed for an optional ambe vocoder (it is NOTcompression).

DVSI chips are TI DSPs that are factory programmed with their code. The interface is 2 SSPs or synchronous serial port which connect directly to the Marvell SOC.

The interface and drivers wil be documented.

Bryan


Tyrell Berry <kd7kuj@...>
 

Again, I'm not an audio engineer, and I have been wrong before...  but isn't saying that the chip is a vocoder and it is not compression kind of like saying MP3 is a Muscoder and is also not compression? Is it somehow true that because someone chooses to use a different vocabulary that the principles of which I speak somehow cease to apply?

It has been said several times before, and I will agree: it's entirely possible that transcoding through back to back vocoders may produce legible audio...  Only one way to find out, and I look forward to hearing recordings of the results.  

On Aug 3, 2012 6:51 AM, "Bryan Hoyer" <bhhoyer@...> wrote:
 

The UDR56K has an expansion interface which is designed for an optional ambe vocoder (it is NOTcompression).

DVSI chips are TI DSPs that are factory programmed with their code. The interface is 2 SSPs or synchronous serial port which connect directly to the Marvell SOC.

The interface and drivers wil be documented.

Bryan

Bryan Hoyer <bhhoyer@...>
 

The UDR56K has an expansion interface which is designed for an optional ambe vocoder (it is NOTcompression).

DVSI chips are TI DSPs that are factory programmed with their code. The interface is 2 SSPs or synchronous serial port which connect directly to the Marvell SOC.

The interface and drivers wil be documented.

Bryan

"Tony Langdon, VK3JED" <vk3jed@...>
 

At 10:29 AM 8/3/2012, you wrote:


Depending on what the bit rate is for NXDN, there may only need to be a conversion to and from D-Star's bit rate; does anyone know that information off-hand? The nice thing is that we probably won't need more than one chip as long as there isn't a need to handle full-duplex digital voice.

For Reid: this is more of a brainstormimg session for a protocol conversion interface than a specific functionality request for the UDR56K. I know that there is some interest in bridging between the Hytera and Motorola DMR implementations, which I'm sure Tyrell can confirm; I see a need for similar bridging between other protocols, even if others don't.
Well, what could be useful here is an interface in the UDR56K that presents the raw digital audio data, so it can be processed by an external AMBE (or whatever) decoder, making an external transcoder easier to implement.

Just contributing in the brainstorming spirit.

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

"Tony Langdon, VK3JED" <vk3jed@...>
 

At 08:52 AM 8/3/2012, you wrote:


Fair enough, I stand corrected. Even as I hit send, I more or less knew I was wrong and should have said simply "uncompressed audio". Still, every time you convert to a lossy format, audio data is lost, and we don't have much to work with from the get-go.
True, but in my experience, there is still a big difference between transcoding to PCM and going all the way to analog and back. With the latter, you add a D/A and A/D converter, you're relying on the antialiasing/reconstruction filters to be good, and the quality of the intervening audio stages (which can be suspect in 2 way radios).

You are right that there are still losses converting between the formats. Only one way to find out if it's too bad or not. ;)

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

Matthew Pitts <daywalker_blade_2004@...>
 

Depending on what the bit rate is for NXDN, there may only need to be a conversion to and from D-Star's bit rate; does anyone know that information off-hand? The nice thing is that we probably won't need more than one chip as long as there isn't a need to handle full-duplex digital voice.

For Reid: this is more of a brainstormimg session for a protocol conversion interface than a specific functionality request for the UDR56K. I know that there is some interest in bridging between the Hytera and Motorola DMR implementations, which I'm sure Tyrell can confirm; I see a need for similar bridging between other protocols, even if others don't.

Matthew Pitts
N8OHU


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From: Tyrell Berry ;
To: ;
Subject: Re: [UniversalDigitalRadio] Re: Bridging the digital voice and data gap
Sent: Thu, Aug 2, 2012 10:52:00 PM

 

Fair enough, I stand corrected.  Even as I hit send, I more or less knew I was wrong and should have said simply "uncompressed audio".  Still, every time you convert to a lossy format, audio data is lost, and we don't have much to work with from the get-go.

On Aug 2, 2012 3:22 PM, "Tony Langdon, VK3JED" <vk3jed@...> wrote:
 

At 06:59 PM 8/2/2012, you wrote:
>___Original Message_________________________________________
>From: "Tony Langdon, VK3JED" <vk3jed@...>
>Date: Thu, 2 Aug 2012 Time: 07:32:08
>
> >There is no analog audio near a DV Dongle (have you
> >ever managed to get an analog signal down a USB bus? ;) ).
>
> >
>
>Yup. I do it every day. On my TS-590S. Mostly analog data tones, but
>sometimes analog DV tones. Audio codec in the radio, codec driver in the
>PC. USB cable in between. Works very well.

But you are NOT passing analog audio down the USB cable. You're
passing digital PCM to a USB sound device built into the
radio. Semantics are important in this discussion, and my point
still stands, there are no analog signals around a DV Dongle, just an
AMBE coded bitstream and a PCM bitstream (plus commands to the dongle
and status/responses back).

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

Tyrell Berry <kd7kuj@...>
 

Fair enough, I stand corrected.  Even as I hit send, I more or less knew I was wrong and should have said simply "uncompressed audio".  Still, every time you convert to a lossy format, audio data is lost, and we don't have much to work with from the get-go.

On Aug 2, 2012 3:22 PM, "Tony Langdon, VK3JED" <vk3jed@...> wrote:
 

At 06:59 PM 8/2/2012, you wrote:
>___Original Message_________________________________________
>From: "Tony Langdon, VK3JED" <vk3jed@...>
>Date: Thu, 2 Aug 2012 Time: 07:32:08
>
> >There is no analog audio near a DV Dongle (have you
> >ever managed to get an analog signal down a USB bus? ;) ).
>
> >
>
>Yup. I do it every day. On my TS-590S. Mostly analog data tones, but
>sometimes analog DV tones. Audio codec in the radio, codec driver in the
>PC. USB cable in between. Works very well.

But you are NOT passing analog audio down the USB cable. You're
passing digital PCM to a USB sound device built into the
radio. Semantics are important in this discussion, and my point
still stands, there are no analog signals around a DV Dongle, just an
AMBE coded bitstream and a PCM bitstream (plus commands to the dongle
and status/responses back).

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

"Tony Langdon, VK3JED" <vk3jed@...>
 

At 06:59 PM 8/2/2012, you wrote:
___Original Message_________________________________________
From: "Tony Langdon, VK3JED" <vk3jed@...>
Date: Thu, 2 Aug 2012 Time: 07:32:08

There is no analog audio near a DV Dongle (have you
ever managed to get an analog signal down a USB bus? ;) ).
>

Yup. I do it every day. On my TS-590S. Mostly analog data tones, but
sometimes analog DV tones. Audio codec in the radio, codec driver in the
PC. USB cable in between. Works very well.
But you are NOT passing analog audio down the USB cable. You're passing digital PCM to a USB sound device built into the radio. Semantics are important in this discussion, and my point still stands, there are no analog signals around a DV Dongle, just an AMBE coded bitstream and a PCM bitstream (plus commands to the dongle and status/responses back).

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

Matthew Pitts <daywalker_blade_2004@...>
 

Yes, there are several high end transceivers that have an integrated sound card specifically for use on the various HF digital modes.

Matthew Pitts
N8OHU

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From: Tony Langdon, VK3JED ;
To: ;
Subject: RE: [UniversalDigitalRadio] Re: Bridging the digital voice and data gap
Sent: Thu, Aug 2, 2012 10:56:09 AM

 

At 12:30 PM 8/2/2012, you wrote:

>Hmm. Not sure how they do it but the IC-7200 passes the audio over a
>USB connection in parallel with the CI-V commands.

Well, that one's easy, the audio is still in digital form, it's
rather like a serial dongle and a sound fob on the one USB hub. :)

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

"Tony Langdon, VK3JED" <vk3jed@...>
 

At 12:30 PM 8/2/2012, you wrote:


Hmm. Not sure how they do it but the IC-7200 passes the audio over a USB connection in parallel with the CI-V commands.
Well, that one's easy, the audio is still in digital form, it's rather like a serial dongle and a sound fob on the one USB hub. :)

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

Ian Wade G3NRW <g3nrw-radio@...>
 

___Original Message_________________________________________
From: "Tony Langdon, VK3JED" <vk3jed@...>
Date: Thu, 2 Aug 2012 Time: 07:32:08

There is no analog audio near a DV Dongle (have you
ever managed to get an analog signal down a USB bus? ;) ).
Yup. I do it every day. On my TS-590S. Mostly analog data tones, but sometimes analog DV tones. Audio codec in the radio, codec driver in the PC. USB cable in between. Works very well.

:-)

--
73
Ian, G3NRW

The TS-590S Resources Page:
http://homepage.ntlworld.com/wadei/ts-590s.htm

The TS-990S Resources Page:
http://homepage.ntlworld.com/wadei/ts-990.htm

"Howard Small" <howard@...>
 

Hmm. Not sure how they do it but the IC-7200 passes the audio over a USB connection in parallel with the CI-V commands.

 

Howard

VK4BS

 

From: UniversalDigitalRadio@... [mailto:UniversalDigitalRadio@...] On Behalf Of qrv@...
Sent: Thursday, 2 August 2012 12:01
To: UniversalDigitalRadio@...
Subject: Re: [UniversalDigitalRadio] Re: Bridging the digital voice and data gap

 

 

This one tickled my fancy ...

Perhaps one could modulate the 5v line?

Just sayin' ... ;-)

> Tony Langdon, VK3JED wrote: (have you ever managed to get an analog
> signal down a USB bus? ;) ).

--

Thanks! & 73, KD4E.com
David Colburn nevils-station.com
I don't google I SEARCH! duckduckgo.com
Network: groups.yahoo.com/group/qrv
Restored to design-spec at Heaven's gate 1Cor15:22

"qrv@..." <qrv@...>
 

This one tickled my fancy ...

Perhaps one could modulate the 5v line?

Just sayin' ... ;-)

Tony Langdon, VK3JED wrote: (have you ever managed to get an analog
signal down a USB bus? ;) ).
--

Thanks! & 73, KD4E.com
David Colburn nevils-station.com
I don't google I SEARCH! duckduckgo.com
Network: groups.yahoo.com/group/qrv
Restored to design-spec at Heaven's gate 1Cor15:22

"Tony Langdon, VK3JED" <vk3jed@...>
 

At 01:43 AM 8/2/2012, you wrote:


Maybe your all confused... audio doesn't have to come out a speaker to be analog. To be perfectly clear, the dv-dongle is still converting a digital signal to an analog one... and a second chip is required to go into any another digital code. Even if a lossless digital codec is used in between (like wave or similar), the conversion to a lossy format like AMBE is the troublesome one... not the conversion to analog. Yes, less signal is lost vs going out a speaker and into a microphone, but the principles I stated before are largely the same, and I'm not convinced the resulting stream of bits will be legible
No, the DV dongle converts a PCM bitstream to an AMBE coded bitstream and vice-versa. There is no analog audio near a DV Dongle (have you ever managed to get an analog signal down a USB bus? ;) ).

Conversions between codecs are better when there is no intervening A/D and D/A pair to go through, so running a DV Dongle (or equivalent) back to back with an IMBE equivalent will give the best result possible. You are right in one thing, the result won't be perfect, may not be pretty, but it may be functional. Only one way to find out! :) If the number of transcodes is limited to the bare minimum (i.e. 1), then you may get along with it.

Oh, and a case in point, telephony systems (e.g. Asterisk) do convert between codecs when necssary, so that you can attach any phone to the system, regardless of what code the network is running. The phone just needs to be capable of using at least one of the codecs Asterisk supports. Asterisk also decodes and recodes any participants in a conference call. Of course, most of the codecs used in telephony are a lot less "aggressive", but the principle works rather well.


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

Tyrell Berry <kd7kuj@...>
 

Maybe your all confused...  audio doesn't have to come out a speaker to be analog.  To be perfectly clear, the dv-dongle is still converting a digital signal to an  analog one...  and a second chip is required to go into any another digital code. Even if a lossless digital codec is used in between (like wave or similar), the conversion to a lossy format like AMBE is the troublesome one...  not the conversion to analog. Yes, less signal is lost vs going out a speaker and into a  microphone, but the principles I stated before are largely the same, and I'm not convinced the resulting stream of bits will be legible audio.

As for the conversion from fdma to tdma, if NAT can convert ip addresses, this should be easy.

On Aug 1, 2012 7:54 AM, "Reid" <reid.crowe@...> wrote:
 

Will the UDR56K4 be able to support the switching speeds required for DMR?

-Reid N0RC

--- In UniversalDigitalRadio@..., Matthew Pitts wrote:
>
> This topic seems more appropriate to this group than any of the others that I'm in here, as the hardware should support at least the three main modes in use. I know some folks might get their knickers in a twist over this, but interoperability between DMR, D-Star and NXDN is something I feel would be of benefit to all digital voice hams, and would eliminate the (intentional) animosity I've seen in certain groups if someone brings up connecting certain "incompatible" hardware together.
>
> I know that the DMR core network standard implies that it is possible to connect a Hytera repeater to a Motorola Mototrbo repeater even though they use incompatible manufacturer specific functions; there are similar potential issues with connecting Icom IDAS repeater to Kenwood NEXEDGE repeaters. D-Star is semi-unique in that it's network protocol is the same as it's over the air protocol, and this is what attracted me to it in the first place, from a hardware and software design perspective. Is anyone else interested in discussion on this subject?
>
> Matthew Pitts
> N8OHU
>
>
> Sent from Yahoo! Mail on Android
>

Bryan Hoyer <bhhoyer@...>
 

Hi Reid,

DMR is NOT one of the modes supported at launch. There has been some interest in DMR mostly in a future duplex repeater configuration which doesn't require turning the PA around.

As a client, the architecture is able to support the timing for TDMA in the FPGA (software lacks the required granularity). and the TX/RX switch is well under the 1.5ms switch time.

So that makes this a definite maybe.

Bryan

"Reid" <reid.crowe@...>
 

Will the UDR56K4 be able to support the switching speeds required for DMR?

-Reid N0RC

--- In UniversalDigitalRadio@..., Matthew Pitts <daywalker_blade_2004@...> wrote:

This topic seems more appropriate to this group than any of the others that I'm in here, as the hardware should support at least the three main modes in use. I know some folks might get their knickers in a twist over this, but interoperability between DMR, D-Star and NXDN is something I feel would be of benefit to all digital voice hams, and would eliminate the (intentional) animosity I've seen in certain groups if someone brings up connecting certain "incompatible" hardware together.

I know that the DMR core network standard implies that it is possible to connect a Hytera repeater to a Motorola Mototrbo repeater even though they use incompatible manufacturer specific functions; there are similar potential issues with connecting Icom IDAS repeater to Kenwood NEXEDGE repeaters. D-Star is semi-unique in that it's network protocol is the same as it's over the air protocol, and this is what attracted me to it in the first place, from a hardware and software design perspective. Is anyone else interested in discussion on this subject?

Matthew Pitts
N8OHU


Sent from Yahoo! Mail on Android

"Tony Langdon, VK3JED" <vk3jed@...>
 

At 07:53 PM 8/1/2012, Matthew Pitts wrote:

Tony,

Exactly; all of the DV technologies I mentioned use some form of AMBE, so it's a matter of conversion of bit rates and constructing the proper carrier code for the target system. We already have code for D-Star amd can write code for DMR and NXDN as well. The hardest part will be converting from FDMA to TDMA and back, as the time slots could both have information on them that needs to be handled in some way.
Agree totally, all the supervisory information needs to be handled properly. I'd like to see this sort of work happen. As for the technologies, I'm wary of TDMA, because it has inherent range limits (since the speed of light is finite), and over here, distance is king.

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

Matthew Pitts <daywalker_blade_2004@...>
 

Tony,

Exactly; all of the DV technologies I mentioned use some form of AMBE, so it's a matter of conversion of bit rates and constructing the proper carrier code for the target system. We already have code for D-Star amd can write code for DMR and NXDN as well. The hardest part will be converting from FDMA to TDMA and back, as the time slots could both have information on them that needs to be handled in some way.

Matthew Pitts
N8OHU

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