ISDN Compatibility

by Norb Gallery, NPR Master Control Supervisor. Revised 980429

Return to Continuing Education | ISDN

This is my first take on everything that you need to know about ISDN Compatibility.

By "compatibility", I mean the ability to transmit audio by ISDN. The issue is compounded by a number of factors such that two codecs will be compatible with certain settings and incompatible with others.
So what makes this true?

Data Rate

The easiest thing to figure out. This will be a multiple of 56 or 64K. Anything above 64K will require multiple calls to the same or different numbers.
Note: Corporate Computer Systems (CCS), is doing business as MUSICAM USA.

Codec 56K 64K 112K 128K 192K 256K 384K
CCS Micro 56

E

 

 

 

 

 

 

CCS Micro 66

E

E

 

 

 

 

 

CCS CDQ-1000

E

E

 

 

 

 

 

CCS-CDQ-2000

E

E

E

E

E

E

E

CCS Prima 1XX

I/E

I/E

I/E

I/E

E

E

E

CCS-Prima 2XX

I/E

I/E

I/E

I/E

I/E

I/E

I/E

CCS RoadRunner

I/E

I/E

I/E

I/E

E

E

E

Comrex Nexus

I

I

I

I

 

 

 

Comrex DX200

E

E

E

E

E

E

E

DolbyFax

E

E

E

E

E

E

E

RE America

E

E

E

E

E

E

E

Telos Zephyr

I/E

I/E

I/E

I/E

 

 

 

I indicates the use of an internal terminal adapter. E indicates an external terminal adapter.

Data Rate  | Inverse Multiplexing | Algorithm | Audio Mode | Sample Rate | Decoder Independence

Inverse Multiplexing

Any scheme that requires more than 64Kbits per second also requires multiple data calls and a method for combining them together. This function can be done either in the terminal adapter or the codec, different manufacturers use different approaches. Generally speaking, codecs with internal terminal adapters do not support bonding in the TA but provide their own solution.  

Codec 2 Ln H221 Bonding

128K

256/384K

128K

256/384K

CCS Micro 56

 

 

 

 

 

CCS Micro 66

 

 

 

 

 

CCS CDQ-1000

 

 

 

 

 

CCS-CDQ-2000

I/D

 

 

B/4

4

CCS Prima 1XX

I/D

I

 

B/4

4

CCS-Prima 2XX

I/D

I

3

B/4

4

CCS RoadRunner

I/D

 

 

B

 

Comrex Nexus

I/D

 

 

I

 

Comrex DX200

D

 

 

B/4

4

DolbyFax

D

 

 

B/4

4

RE America

D

 

 

B/4

4

Telos Zephyr

I/D

 

 

B

 

 

I = Internal TA

 

B = External TA with Bonding;
       Adtran ISU-128, Adtran ISU-2X64 		1 BRI up to 128K
D = External TA with Independent DTEs;
       Adtran ISU-2X64		 1 BRI up to 128K
3 = 3 Internal Terminal Adapters 3 BRI up to 384K
4 = External TA with Four BRIs;
      Adtran ISU-512, Ascend VSX 		4 BRI up to 512K

It is imperative that the sending and receiving ends use the same scheme.

Data Rate  | Inverse Multiplexing | Algorithm | Audio Mode | Sample Rate | Decoder Independence

Algorithm

There are several different algorithms in common usage for broadcasting. First lets talk about what they are before we discuss who supports what.

G.722

The first algorithm in common use. ADPCM (Adaptive Delta Pulse Code Modulation) samples at 16KHz and uses only 1 ISDN B Channel. Can only provide frequency response up to 8Khz and tends to have considerable artifacts but very short processing delay. Often included in modern codecs compatibility as a lowest-common-denominator.

 

G.722
Turbo

Comrex is the only adherent to this "standard" A variant of G.722 that uses a sample rate of 32KHz to yield up to 15Khz frequency response using two ISDN B Channels. Has low processing delay.

 

MPEG
Layer 2

A Perceptive coding scheme that is optimized for 128K/audio channel.

 

CCS
Old

A variant of MPEG Layer 2 developed for the CCS CDQ-2000.

 

CCS
New

A variant of MPEG Layer 2 developed for the CCS CDQ-1000.

 

MPEG
Layer 3

An extremely complex perceptive coding scheme using 576 frequency bands.

 

Dolby
AC-2

The same coding scheme used for Dolby Digital in Theaters.

 

Dolby
AC-3

The same coding scheme used in DVDs and Digital Broadcast Television.

 

APT
X-100

A High-BitRate version of ADPCM, most often used by recording studios.
Both EDnet and GlobeCast offer bridge services (at, in our opinion, a considerable cost).

 

NPR supports all those listed below with the exception of APT X-100 and G.722 Turbo.  

Codec G.722 G.722 Turbo CCS-O CCS-N MPEG2 MPEG3 AC-2 AC-3 APT-X
CCS Micro 56

X

 

 

 

 

 

 

 

 

CCS Micro 66

X

 

 

 

 

 

 

 

 

CCS CDQ-1000

X

 

 

X

 

 

 

 

 

CCS-CDQ-2000

 

 

X

 

 

 

 

 

 

CCS Prima

X

 

X

X

X

X

 

 

 

CCS RoadRunner

X

 

X

X

X

X

 

 

 

Comrex Nexus

X

X

 

 

 

 

 

 

 

Comrex DX200

X

X

 

 

X

 

 

 

 

DolbyFax

 

 

 

 

X

 

X

X

 

RE America

X

 

 

 

X

 

 

 

 

Telos Zephyr

X

 

 

 

X

X

 

 

 

Data Rate  | Inverse Multiplexing | Algorithm | Audio Mode | Sample Rate | Decoder Independence

Audio Mode

Any codec capable of bitrates above 64K is also capable of various audio modes. While some decoders can detect what the encoder is sending, it is prudent to pre-configure your decoder for the desired settings.

These are the most likely terms you will encounter.  

Mono One Channel of audio usually using a single data channel (64K)
Mono 128K One Channel of audio using two B channels (128K)
Dual Two independent channels of Audio each allocated one half of the available bitrate.
Joint Stereo Two related channels of audio with shared information are encoded to minimize the amount of duplicated data.
Stereo Two related channels of audio each of which is allocated one half of the available bitrate.

Data Rate  | Inverse Multiplexing | Algorithm | Audio Mode | Sample Rate | Decoder Independence

Sample Rate

Sometimes two different codecs will share a common algorithm, but will support a different group of sample rates.  

Codec

G.722

Layer 2

Layer 3

16K

16K

22K

24K

32K

44.1K

48K

16K

24K

32K

48K

CCS Micro 56

X

 

 

 

 

 

 

 

 

 

 

CCS Micro 66

X

 

 

 

 

 

 

 

 

 

 

CCS CDQ-1000

X

 

 

X

 

 

X

 

 

 

 

CCS CDQ-2000

 

 

 

 

 

 

X

 

 

 

 

CCS Prima 1XX

X

X

X

X

X

X

X

X

X

X

X

CCS Prima 2XX

X

X

X

X

X

X

X

X

X

X

X

CCS RoadRunner

X

X

 

X

X

 

X

X

X

X

X

Comrex Nexus

X

 

 

 

 

 

 

 

 

 

 

Comrex DX200

X

 

 

X

 X

 

X

 

 

 

 

DolbyFax

 

 

 

 

X

X

X

 

 

 

 

RE America

X

X

X

X

X

X

X

 

 

 

 

Telos Zephyr

X

 

 

 

 

 

X

 

 

X

X

Data Rate  | Inverse Multiplexing | Algorithm | Audio Mode | Sample Rate | Decoder Independence

Decoder Independence

A feature of the higher bit-rate MUSICAM USA codecs is the ability for the decoder to determine its configuration depending on the setting of the encoder. This mode is called Decoder Dependent and is not supported by any other manufacturer.

It is imperative when connecting a MUSICAM USA codec to any other manufacturer's product that the MUSICAM USA codec be placed in the Decoder Independent mode.

This is done differently on the three MUSICAM USA products in the NPR inventory.

Codec Decoder Independent Setting
RoadRunner [Advanced] [Decoder] [Independent] [Yes]
Prima [Decoder] [Independent] [Yes]
CDQ-2000 DIP Switch 6 on the Decoder (bottom box, rear panel) Up.

Data Rate   | Inverse Multiplexing | Algorithm | Audio Mode | Sample Rate | Decoder Independence

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