Iec 61603-7-2003.Pdf

INTERNATIONAL STANDARD IEC 61603 7 First edition 2003 05 Transmission systems of audio and/or video and related signals using infra red radiation – Part 7 Digital audio signals for conference and simi[.]

STANDARD 61603-7

First edition2003-05

Transmission systems of audio and/or video and

related signals using infra-red radiation –

Part 7:

Digital audio signals for conference and

similar applications

Reference numberIEC 61603-7:2003(E)

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STANDARD 61603-7

First edition2003-05

Transmission systems of audio and/or video and

related signals using infra-red radiation –

Part 7:

Digital audio signals for conference and

similar applications

 IEC 2003  Copyright - all rights reserved

No part of this publication may be reproduced or utilized in any form or by any means, electronic or

mechanical, including photocopying and microfilm, without permission in writing from the publisher.

International Electrotechnical Commission, 3, rue de Varembé, PO Box 131, CH-1211 Geneva 20, Switzerland

Telephone: +41 22 919 02 11 Telefax: +41 22 919 03 00 E-mail: inmail@iec.ch Web: www.iec.ch

U

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Commission Electrotechnique Internationale

International Electrotechnical Commission

Международная Электротехническая Комиссия

FOREWORD 4

1 Scope 5

2 Normative references 5

3 Terms and definitions 5

4 Abbreviations 5

5 Explanation of terms and general information 6

6 System considerations 6

7 Basic system concept 6

8 Protocol 7

8.1 System context 7

8.2 Physical layer 8

8.3 Data link layer 13

8.4 Detailed overview of audio frame structures 15

9 Data protocol 17

9.1 General 17

9.2 Data messages 18

9.3 Data packet structure 21

Annex A (normative) Definition of prototype filter 23

Annex B (informative) Example of λ/f diagram in the user area conference 24

Annex C (informative) Provision for future developments 25

Bibliography 26

Figure 1 – System 7

Figure 2 – Conceptual model 7

Figure 3 – Band allocation for 6 modulated sub-carriers 8

Figure 4 – (D)QPSK constellation and differential decoding algorithm 9

Figure 5 – Pulse response of a raised cosine channel filter 10

Figure 6 – Scrambler 11

Figure 7 – Block diagram of sub-band APCM encoder 12

Figure 8 – Quantization of sub-band samples 13

Figure 9 – Superframe structure 14

Figure 10 – RS frame structure 14

Figure 11 – Audio block structure 15

Figure 12 – CRC calculation 15

Figure 13 – Audio block structure for medium quality 16

Figure 14 – Bit-pool sample structure for medium quality 16

Figure 15 – Audio block structure for high quality 16

Figure 16 – Bit-pool sample structure for high quality 17

Figure 17 – Positioning of the data protocol 18

Figure 18 – Data message build-up 18

Figure 19 – Configuration message structure 19

Figure 20 – Display message structure for ASCII display data 20

Figure 21 – Display message structure for bitmap display data 21

Figure 22 – Segmentation of data messages 21

Figure 23 – Data packets fitted on to the superframe structure 22

Table 1 – Sub-carrier centre frequencies 8

Table 2 – Phase transitions of the differential encoding algorithm 9

Table 3 – Characteristics of sub-band APCM encoder 12

Table 4 – Definition of audio mode bits 15

Table 5 – Audio blocks and audio quality 17

Table 6 – Data message identifier definition 18

Table 7 – SCI definition 19

Table 8 – Channel allocation table 19

Table 9 – Audio quality mode (AQM) to number of audio blocks used 20

Table C.1 – Sub-carrier allocation 25

INTERNATIONAL ELECTROTECHNICAL COMMISSION

_

TRANSMISSION SYSTEMS OF AUDIO AND/OR VIDEO

AND RELATED SIGNALS USING INFRA-RED RADIATION –

Part 7: Digital audio signals for conference and

similar applications

FOREWORD1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization comprising

all national electrotechnical committees (IEC National Committees) The object of the IEC is to promote

international co-operation on all questions concerning standardization in the electrical and electronic fields To

this end and in addition to other activities, the IEC publishes International Standards Their preparation is

entrusted to technical committees; any IEC National Committee interested in the subject dealt with may

participate in this preparatory work International, governmental and non-governmental organizations liaising

with the IEC also participate in this preparation The IEC collaborates closely with the International

Organization for Standardization (ISO) in accordance with conditions determined by agreement between the

two organizations.

2) The formal decisions or agreements of the IEC on technical matters express, as nearly as possible, an

international consensus of opinion on the relevant subjects since each technical committee has representation

from all interested National Committees.

3) The documents produced have the form of recommendations for international use and are published in the form

of standards, technical specifications, technical reports or guides and they are accepted by the National

Committees in that sense.

4) In order to promote international unification, IEC National Committees undertake to apply IEC International

Standards transparently to the maximum extent possible in their national and regional standards Any

divergence between the IEC Standard and the corresponding national or regional standard shall be clearly

indicated in the latter.

5) The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any

equipment declared to be in conformity with one of its standards.

6) Attention is drawn to the possibility that some of the elements of this International Standard may be the subject

of patent rights The IEC shall not be held responsible for identifying any or all such patent rights.

International Standard IEC 61603-7 has been prepared by Technical Area 3, Infrared systems

and applications, of IEC technical committee 100: Audio, video and multimedia systems and

equipment

This first edition cancels and replaces 2.6.2 of IEC 61603-3 (1997)

The text of this standard is based on the following documents:

Full information on the voting for the approval of this standard can be found in the report on

voting indicated in the above table

This publication has been drafted in accordance with the ISO/IEC Directives, Part 2

The committee has decided that the contents of this publication will remain unchanged until 2005

At this date, the publication will be

TRANSMISSION SYSTEMS OF AUDIO AND/OR VIDEO

AND RELATED SIGNALS USING INFRA-RED RADIATION –

Part 7: Digital audio signals for conference and

similar applications

1 Scope

This part of IEC 61603 describes the characteristics of a digital multiple channel, multiple

carrier audio transmission system as an extension to conference interpretation or similar

systems using the frequency ranges 45 kHz to 1 MHz and 2 MHz to 6 MHz

NOTE These frequency ranges are also covered by analogue pulse systems used for the same applications.

Interference is not expected because both transmission systems are normally not applied at the same time in the

same room.

2 Normative references

The following referenced documents are indispensable for the application of this document

For dated references, only the edition cited applies For undated references, the latest edition

of the referenced document (including any amendments) applies

IEC 61603-1:1997, Transmission of audio and/or video and related signals using infrared

radiation – Part 1: General

IEC 61603-3:1997, Transmission of audio and/or video and related signals using infrared

radiation – Part 3: Transmission systems for audio signals for conference and similar systems

ISO/IEC 7498-1:1994, Information technology – Open Systems Interconnection – Basic

Reference Model: The Basic Model

3 Terms and definitions

For the purposes of this document, the terms and definitions given in IEC 61603-1 apply

4 Abbreviations

_

1 To be published For the purposes of the reference in C.1, IEC 61920:1998 is equally valid.

DMI Data message identifier

5 Explanation of terms and general information

For the purposes of this part of IEC 61603, the explanation and information given in

IEC 61603-3, Clause 2, apply

6 System considerations

For the purposes of this part of IEC 61603, the considerations given in IEC 61603-3, Clause

3, apply

NOTE With regard to the primary band, the special caution advised in IEC 61603-3, 3.3 should be observed,

especially for inductive lighting and future developments.

7 Basic system concept

The basic system concept is shown in Figure 1

The system consists of a number (N) of audio sources, either analogue or digital, which are

connected to a transmitter The transmitter processes the audio signals (in accordance with

the protocol described in Clause 8) into an electrical output to feed the infrared radiator The

infrared signal is received by the infrared receiver that processes the signal and outputs an

audio signal and/or associated data

Infrared

Audiosource sourceAudio sourceAudio sourceAudio

Figure 2 – Conceptual model

Figure 2 shows the system context using the OSI reference model Layers 1 and 2 will be part

of the transmission protocol defined in this standard

Data link layer (layer 2)

IEC 61603-7

Physical layer (layer 1) IEC 61603-1

IEC 61920

(low rate, limited)

Higher OSI protocol

Medium

IEC 1548/03

IEC 1549/03

8.2 Physical layer

8.2.1 General

OSI layer 1 (physical layer) shall use infrared radiation as the transfer medium between

radiator and receiver as specified in IEC 61920 and IEC 61603-1

8.2.2 Carrier

8.2.3 Sub-carriers

Secondary frequency band (band II): 45 kHz – 1 MHz

NOTE The secondary frequency band, 45 kHz to 1 MHz, is under consideration.

Figure 3 shows the wideband allocation in the primary band, with the frequencies of each

sub-carrier A guard band between the transmission bands has been included Table 1 shows the

frequencies of each sub-carrier

Guardband

Figure 3 – Band allocation for 6 modulated sub-carriers

Table 1 – Sub-carrier centre frequencies

where

occ

IEC 1550/03

8.2.5 Sub-carrier modulation

The modulation method is (D)QPSK The constellation is shown in Figure 4a The differential

decoding algorithm is shown in Figure 4b The phase transitions for the differential encoding

algorithm are also listed in Table 2

Figure 4 – (D)QPSK constellation and differential decoding algorithm

Table 2 – Phase transitions of the differential

A channel filter is included A square root raised cosine (SRRC) characteristic, as illustrated

in Figure 5, is implemented in both the transmitter and the receiver resulting in a total transfer

characteristic of a raised cosine

a)

11 01

IQ

10 00

01 11

00 10

01 11

11 11

01 01

IEC 1551/03

Figure 5 – Pulse response of a raised cosine channel filter

The combined filter characteristic from the transmitting and receiving filter shall be in

accordance with the following equation:

( 2 )

( 2 ) ( 2 cos

) ( 2 )

(

b

bb

b2

b

bb

r

β

β β

β β

π

β

1 0

1 1

1 4

1

r f

r f r

r f T

r f T

f P

A shorted Solomon encoder (n,k,d) = (28,24,5) on 8-bit symbols is used The

The field generator polynomial is:

( )x =x +x +x +x2+1

IEC 1552/03

The code generator polynomial is:

i

α

x x

g

6 78 2 249 3 75

8.2.7.2 Scrambler

The scrambler consists of an XOR gate and a pseudo-random binary sequence (PRBS)

generator The length of the PRBS is 11 bits and is initialized after every frame sync The

polynomial that is used for the PRBS is

(analysis) filter bank The 4 sub-band signals are decimated by a factor 4 and quantized

by an adaptive pulse code modulation (APCM) coding scheme A block diagram of the

encoder is shown in Figure 7

IEC 1553/03

APCM encode

APCM encode

APCM encode

APCM encode

x(n)

Linear PCM samples

Bit multi- plexer

Figure 7 – Block diagram of sub-band APCM encoder

Two coding qualities are available: medium quality (MQ) and high quality (HQ) The

characteristics are shown in Table 3

Table 3 – Characteristics of sub-band APCM encoder

( )k n c ( ) ( )k n p n

h , = a , ×with

c a cos π

8.2.8.3 Sub-band APCM coding

4 blocks of 6 sub-band samples are filled and available for APCM coding

The sub-band APCM coding operates on 16 bit samples and performs the steps listed below

NOTE At the output of the decimators all samples have to be quantized to 16 bits.

( )k  (M( )k ) 

Fscale = 2log

IEC 1554/03

c) From the SF values, the number of bits per sub-band is calculated: nbits( )k ←Fscale( )k

− nbits( )k =max(Fscale( )k −W,0)

∀

=

k

B k

7-bit quantized sample16-bit sample

Figure 8 – Quantization of sub-band samples

The output of the sub-band APCM coder consists of all quantized sub-band samples together

with the scale factors

8.3 Data link layer

8.3.1 General

The major building block of the data link layer protocol is a superframe (see Figure 9)

IEC 1555/03

Sub-band samples (66 bits)

Scale factors (8 bits)

Audio mode (1 bit)

CRC (5 bits)

1 audio block (10 bytes)

Audio block A (10 bytes)

1 RS frame (28 bytes)

Audio block B (10 bytes)

DATA (4 bytes)

RS parity (4 bytes)

RS frame 0 (28 bytes)

RS frame 1 (28 bytes)

RS frame 2 (28 bytes)

RS frame 3 (28 bytes)

RS frame 4 (28 bytes)

RS frame 5 (28 bytes)

SYNC

(3 bytes)

1 superframe (1 368 bits) ; 1,632 ms

Figure 9 – Superframe structure

A superframe consists of a SYNC pattern followed by 6 RS frames This results in a size of

1 368 bits per superframe With a bit-rate of 837,9 kbit/s, the total length of a superframe is

1,632 ms This is exactly 3 times the length of an APCM frame (at the input of an encoder)

8.3.2 Synchronization information

Before 6 consecutive RS frames a SYNC word is transmitted The SYNC word equals the

hexadecimal value D21DB8

8.3.3 Error coding redundancy

A Reed-Solomon encoder is applied to protect the audio and data information from

transmission errors The Reed-Solomon encoder adds 4 bytes of redundant information, to

chosen (see 8.2.7) The structure of an RS frame is shown in Figure 10

Audio block A (10 bytes)

1 RS frame (28 bytes)

Audio block B (10 bytes)

DATA (4 bytes)

RS parity (4 bytes)

Figure 10 – RS frame structure 8.3.4 Audio blocks

One audio block carries 10 bytes of audio information These 80 bits are divided into 66 bits

for APCM sub-band samples, 8 bits for APCM scale factors, 1 bit for the audio mode, and

5 bits for the CRC protection on the scale factor and audio mode bits The structure of an

audio block is shown in Figure 11

IEC 1556/03

IEC 1557/03