SIST ETS 300 145 E1:2003
(Main)Integrated Services Digital Network (ISDN); Audiovisual services Videotelephone systems and terminal equipment operating on one or two 64 kbit/s channels
- Abstract
To specify system aspects of a narrowband visual telephone system.
- Status
- Published
- Publication Date
- 30-Nov-2003
- Current Stage
- 6060 - National Implementation/Publication (Adopted Project)
- Start Date
- 01-Dec-2003
- Due Date
- 01-Dec-2003
- Completion Date
- 01-Dec-2003
SIST ETS 300 145 E1:2003 is the Slovenian publication of ETS 300 145 Edition 1 from SIST/ETSI. It specifies system requirements for a narrowband videotelephone system operating on one or two 64 kbit/s channels on pan-European ISDN basic access. In practice, it tells terminal makers, MCU suppliers, network engineers and test teams how such equipment establishes calls, exchanges capabilities, switches modes and interworks with related ISDN and telephony services.
What does SIST ETS 300 145 E1:2003 specify?
SIST ETS 300 145 E1:2003 specifies the system requirements for a videotelephone using one or two B-channels when connected to the S point, or coincident S and T reference point, of pan-European ISDN. The focus is system behaviour: call set-up, mode negotiation, communication modes, supplementary-service handling, optional enhancements and fault indication.
The document is organized into these main clauses:
- Clause 1 Scope
- Clause 2 Normative references
- Clause 3 Definitions
- Clause 4 Symbols and abbreviations
- Clause 5 System description
- Clause 6 Terminal procedures
- Clause 7 Optional enhancements
- Clause 8 Fault indication
Annex A is informative and gives a bibliography. The standard relies on other ETSI and ITU-T documents for the detailed signalling syntax, frame structure, video coding and related audio and service functions.
What are the key requirements of SIST ETS 300 145 E1:2003?
Clause 5 sets the basic operating context: a videotelephone to this standard uses at most two B-channels at a time on ISDN basic access, and 2B-capable terminals must also be able to operate in 1B mode. That matters because products have to remain interoperable when only one channel is available, or when a call falls back from two channels to one.
Call establishment follows defined phases
Clause 6 divides a call into phases A, B, CA, CB, C and D/E. The initial channel is set up by D-channel signalling, then mode initialisation uses in-band signalling, and any additional channel is set up and initialised in the same structured way. For implementers, this means the call-control state machine has to match the phase sequence or the terminal will not interwork correctly.
Capability exchange determines the working mode
During phase B, terminals exchange capabilities and select the most appropriate common mode. Clause 5.2 and Table 1 classify terminals by audio mode and by 1B or 2B capability, while Clause 5.3.4 and Table 3 define the communication modes a0, a1, b1, b2 and b3. In practice, the terminal must advertise what it can do and then adapt the connection to the shared audio and video mode.
Frame structure and in-band signalling are fixed by related ETSs
Clause 5.3.1 requires conformance to ETS 300 144 for frame structure, and Clause 5.3.3 requires ETS 300 143 for point-to-point in-band signalling. This matters because the terminal cannot invent its own channel framing or signalling codes - it has to use the same BAS-based procedures as other compliant equipment.
Control and Indication signals cover video, audio, maintenance and MCU functions
Clause 5.3.2 defines which Control and Indication (C&I) signals are used, and Table 2 marks which ones are mandatory. These include picture-format control, freeze-picture requests, video active/suppressed indication, audio active/muted indication, maintenance loop requests, and MCU-related commands. In practice, the terminal must both generate and recognize the C&I messages that keep the session synchronized.
Mode switching must preserve usability
Clause 6.2.1 allows mode switching when user actions change the best operating mode, and it restricts switching to an unframed I-channel mode to situations such as hold or clearing. Clause 6.2.4.1 also requires a terminal to disable its video decoder when the rate is too low or too high for decoding, then re-enable it when decoding becomes possible again. The practical point is that the system must avoid sudden loss of frame alignment and must recover cleanly when the rate changes.
Supplementary services are handled without false fault recovery
Clause 6.3 covers HOLD, Terminal Portability and Explicit Call Transfer. Before these services are invoked, the terminal first prepares the connection with procedure P so that the receiving side sees an expected loss of framing rather than a fault. That is important because the terminal should not trigger unnecessary error recovery when the network deliberately interrupts a channel.
Optional enhancements include data ports and encryption
Clause 7 defines optional data ports and encryption. Data ports are activated and deactivated by BAS commands, while encryption uses the ECS channel and CCITT Recommendation H.233 once both terminals support the same algorithm. For users, this means extra equipment can be attached during a session, and confidentiality can be added after phase B if both ends agree.
Fault indication has to be user-friendly
Clause 8 requires the terminal to follow ETS 300 143 fault procedures and to show the user whether action is needed. If service is temporarily reduced while recovery is underway, the terminal should indicate that no user action is required; if recovery needs user action, the terminal must say so. That helps operators and users distinguish a transient recovery from a real problem.
What terms does SIST ETS 300 145 E1:2003 define?
- Additional channel - one of the channels between two users that is not the I-channel, so it is the second channel in a 2B call.
- Audio mute - muting the loudspeaker of a terminal, which is used when the user wants to silence received audio.
- C&I (Control and Indication) - end-to-end signalling between terminals, with Control changing the remote state and Indication reporting system state or function.
- ECS (Encryption Control Signal) - the signal used to open and control the encryption channel.
- I-channel - the initial or only B-channel used by the call.
- In-band signalling - signalling sent through the BAS of the frame structure rather than through the D-channel.
- MCU (Multipoint Control Unit) - the unit that supports multipoint videotelephone operation.
- Lip synchronisation - keeping the displayed speaking motion aligned with the speech users hear.
Who uses SIST ETS 300 145 E1:2003?
SIST ETS 300 145 E1:2003 is used by manufacturers of videotelephone terminals, audio-video codec vendors, MCU suppliers and designers of ISDN user equipment. It is also relevant to network equipment engineers who implement call control and interworking, and to test laboratories that verify interoperability, mode switching, supplementary services and fault indication.
Quality managers and buyers use it to check whether a product supports the required 1B and 2B behaviour, the expected ISDN signalling, and the related service interactions. Service providers and integration engineers use it when they need videotelephone terminals to work with telephony 3.1 kHz, telephony 7 kHz, G.725-related terminals and PSTN telephony where the standard allows it.
What changed in SIST ETS 300 145 E1:2003 from the previous edition?
SIST ETS 300 145 E1:2003 is identified as identical to ETS 300 145 Edition 1.
Which standards are used with SIST ETS 300 145 E1:2003?
- ETS 300 012 - basic user-network interface layer 1 and test principles for ISDN access.
- ETS 300 102-1 - layer 3 basic call control and D-channel signalling.
- ETS 300 125 - user-network interface data link layer specification.
- ETS 300 143 - in-band signalling procedures and the mode procedures used throughout the call phases.
- ETS 300 144 - frame structure for the 64 to 1 920 kbit/s channel, BAS syntax and related signalling.
- ETS 300 267 - DSS1 procedures for telephony 7 kHz and videotelephony teleservices.
- ITU-T Recommendation H.261 - video coding for audiovisual services at p x 64 kbit/s.
- CCITT Recommendation G.711, G.722 and G.728 - audio coding options used by the defined communication modes.
- CCITT Recommendation H.233 - confidentiality system used when encryption is enabled.
What does the SIST ETS 300 145 E1:2003 document contain?
The document contains a block diagram of a generic videotelephony system, tables for terminal types, C&I signals and communication modes, and detailed phase-by-phase procedures for call establishment, mode initialisation, call clearing and supplementary services. It also includes optional procedures for maintenance loopbacks, mutual video activation, delay compensation, data ports and encryption.
For engineering and test work, the useful parts are the tables that map terminal capability to mode selection, and the procedures that show when a terminal must send or accept BAS commands, D-channel messages and capability exchanges. Annex A provides the bibliography used by the standard.
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Frequently Asked Questions
SIST ETS 300 145 E1:2003 is a standard published by the Slovenian Institute for Standardization (SIST). Its full title is "Integrated Services Digital Network (ISDN); Audiovisual services Videotelephone systems and terminal equipment operating on one or two 64 kbit/s channels". This standard covers: To specify system aspects of a narrowband visual telephone system.
To specify system aspects of a narrowband visual telephone system.
SIST ETS 300 145 E1:2003 is classified under the following ICS (International Classification for Standards) categories: 33.080 - Integrated Services Digital Network (ISDN). The ICS classification helps identify the subject area and facilitates finding related standards.
SIST ETS 300 145 E1:2003 is available in PDF format for immediate download after purchase. The document can be added to your cart and obtained through the secure checkout process. Digital delivery ensures instant access to the complete standard document.
Standards Content (Sample)
SLOVENSKI STANDARD
01-december-2003
Digitalno omrežje z integriranimi storitvami (ISDN) – Avdiovizualne storitve –
Videotelefonski sistemi in terminalska oprema, ki delujejo z enim ali dvema
kanaloma s hitrostjo 64 kbit/s
Integrated Services Digital Network (ISDN); Audiovisual services Videotelephone
systems and terminal equipment operating on one or two 64 kbit/s channels
Ta slovenski standard je istoveten z: ETS 300 145 Edition 1
ICS:
33.080 Digitalno omrežje z Integrated Services Digital
integriranimi storitvami Network (ISDN)
(ISDN)
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
EUROPEAN ETS 300 145
TELECOMMUNICATION May 1994
STANDARD
Source: ETSI TC-TE Reference: DE/TE-04118
ICS: 33.080
ISDN, audiovisual services
Key words:
Integrated Services Digital Network (ISDN);
Audiovisual services
Videotelephone systems and terminal equipment operating
on one or two 64 kbit/s channels
ETSI
European Telecommunications Standards Institute
ETSI Secretariat
F-06921 Sophia Antipolis CEDEX - FRANCE
Postal address:
650 Route des Lucioles - Sophia Antipolis - Valbonne - FRANCE
Office address:
c=fr, a=atlas, p=etsi, s=secretariat - secretariat@etsi.fr
X.400: Internet:
Tel.: +33 92 94 42 00 - Fax: +33 93 65 47 16
Copyright Notification: No part may be reproduced except as authorized by written permission. The copyright and the
foregoing restriction extend to reproduction in all media.
© European Telecommunications Standards Institute 1994. All rights reserved.
New presentation - see History box
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ETS 300 145: May 1994
Whilst every care has been taken in the preparation and publication of this document, errors in content,
typographical or otherwise, may occur. If you have comments concerning its accuracy, please write to
"ETSI Editing and Committee Support Dept." at the address shown on the title page.
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ETS 300 145: May 1994
Contents
Foreword .5
1 Scope .7
2 Normative references.7
3 Definitions.8
4 Symbols and abbreviations .9
5 System description.9
5.1 Block diagram and identification of elements (informative) .9
5.2 Videotelephone terminal types.10
5.3 Signal structure and procedures.11
5.3.1 Frame structure.11
5.3.2 Control and Indication (C&I) .11
5.3.3 Inband signalling procedures .13
5.3.4 Communication modes of videotelephones .13
6 Terminal procedures .14
6.1 Call establishment and mode initialisation.14
6.1.1 Phase A - Call set-up for the initial channel .14
6.1.2 Phase B - mode initialisation .15
6.1.3 Phase CA - call set-up for the additional channel .16
6.1.4 Phase CB - mode initialisation on the additional channel .16
6.2 Phase C - videotelephone communication .16
6.2.1 Mode switching.16
6.2.2 Capability change.17
6.2.3 Loopbacks for maintenance purposes (optional) .17
6.2.4 Terminal arrangements.18
6.2.4.1 Video.18
6.2.4.2 Exchange of video by mutual agreement (optional) .18
6.2.4.3 Delay compensation (optional) .18
6.3 Changes of communication involving D-channel and in-band signalling.18
6.3.1 Supplementary services (optional) .18
6.3.1.1 HOLD.19
6.3.1.1.1 Invocation procedure .19
6.3.1.1.2 Retrieval after invocation of HOLD .19
6.3.1.2 Terminal Portability.19
6.3.1.2.1 Invocation procedure .19
6.3.1.2.2 Resumption after invocation of
Terminal Portability .19
6.3.1.3 Explicit Call Transfer, invocation procedure .20
6.3.2 Change of connection arrangements .20
6.3.2.1 Expanding a 1B call to a 2B call .20
6.3.2.2 Reducing a 2B call to a 1B call.21
6.4 Phase D/E - call clearing.21
6.4.1 Clearing terminal .21
6.4.2 Cleared terminal.22
7 Optional enhancements .22
7.1 Data ports .22
7.2 Encryption .22
8 Fault indication .22
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ETS 300 145: May 1994
Annex A (informative): Bibliography . 23
History. 24
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ETS 300 145: May 1994
Foreword
This European Telecommunication Standard (ETS) has been produced by the Terminal Equipment (TE)
Technical Committee of the European Telecommunications Standards Institute (ETSI).
The attention of the user of this ETS is drawn to the possibility that compliance may require the use of
technology covered by patent or similar rights.
ETSI is not responsible for identifying patent or similar rights or for granting licenses which may be
required and, as a result, ETSI is not in a position to give authoritative or comprehensive information
concerning the existence, validity or scope of patent or similar rights in connection with this ETS.
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ETS 300 145: May 1994
Blank page
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ETS 300 145: May 1994
1 Scope
This ETS specifies the system requirements for a videotelephone using one or two B-channels, when
connected to the S point or coincident S and T reference point of the pan-European Integrated Services
Digital Network (ISDN). These requirements ensure end-to-end compatibility of terminals supporting the
videotelephony teleservice to ETS 300 264 [9].
Conformance to this ETS allows interworking with terminals supporting telephony 3,1 kHz teleservice to
ETS 300 111 [3], telephony 7 kHz teleservice to ETS 300 263 [8], terminals to CCITT Recommendation
G.725 [13], and Public Switched Telephone Network (PSTN) telephony. Interworking with other audio-
visual terminals can take place if their operation on one or two B-channels is according to this ETS.
This ETS is applicable to terminal equipment and other equipment supporting the videotelephony service,
such as multipoint conference units.
Interworking with terminals not connected to an ISDN may be possible if one or two 64 kbit/s (unrestricted
or restricted) digital channels can be established between the two terminals.
The inband signalling procedures are described in ETS 300 143 [6], and the syntax for these procedures
is defined in ETS 300 144 [7]. The video coding algorithm is described in ITU-T Recommendation H.261
[5].
NOTE: Interworking with terminals to CCITT Recommendation G.725 [13] may be restricted to
mode 0.
2 Normative references
This ETS incorporates, by dated or undated reference, provisions from other publications. These
normative references are cited at the appropriate places in the text and the publications are listed
hereafter. For dated references, subsequent amendments to or revisions of any of these publications
apply to this ETS only when incorporated in it by amendment or revision. For undated references the latest
edition of the publication referred to apply.
[1] ETS 300 012 (1991): "Integrated Services Digital Network (ISDN); Basic user-
network interface, Layer 1 specification and test principles".
[2] ETS 300 102-1: "Integrated Services Digital Network (ISDN); User-network
interface, layer 3, Specifications for basic call control".
[3] ETS 300 111 (1992): "Integrated Services Digital Network (ISDN); Telephony
3,1 kHz teleservice, Service description".
[4] ETS 300 125 (1991): "Integrated Services Digital Network (ISDN); User-network
interface data link layer specification, Application of CCITT Recommendations
Q. 920/I. 440 and Q. 921/I. 441".
[5] ITU-T Recommendation H.261 (1993): "Video codec for audiovisual services at
p x 64 Kbit/s".
[6] ETS 300 143: "Integrated Services Digital Network (ISDN): Audiovisual services;
Inband signalling procedures for audiovisual terminals using digital channels up
to 2 048 kbit/s".
[7] ETS 300 144: "Integrated Services Digital Network (ISDN): Audiovisual services;
Frame structure for a 64 to 1 920 kbit/s channel and associated syntax for
inband signalling".
[8] ETS 300 263: "Integrated Services Digital Network (ISDN): Telephony 7 kHz
teleservice, Service description".
[9] ETS 300 264: "Integrated Services Digital Network (ISDN): Videotelephony
teleservice; Service description".
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ETS 300 145: May 1994
[10] ETS 300 267: "Integrated Services Digital Network (ISDN); Telephony 7 kHz
and videotelephony teleservices, Digital Subscriber Signalling System No. one
(DSS1)".
[11] CCITT Recommendation G.711 (1988): "Pulse code modulation (PCM) of voice
frequencies".
[12] CCITT Recommendation G.722 (1988): "7 kHz audio-coding within 64 kbit/s".
[13] CCITT Recommendation G.725 (1988): "System aspects for the use of the 7
kHz audio codec within 64 kbit/s".
[14] CCITT Recommendation G.728 (1992): "Coding of speech at 16 kbit/s using
low-delay code-excited linear prediction".
[15] CCITT Recommendation H.100 (1984): "Visual telephone systems".
[16] CCITT Recommendation H.233 (1992): "Confidentiality system for audiovisual
services".
3 Definitions
For the purposes of this ETS the definitions given in Clause 3 of both ETS 300 143 [6] and ETS 300 144
[7] apply along with the following.
Additional channel: one of the channels between two users, which is not the I-channel (see ETS 300
144 [7]).
Audio mute: muting the loudspeaker of a terminal.
Channel: a unidirectional link between two users.
Connection: a bi-directional link between two users: it carries both (unidirectional) channels.
Control and Indication (C&I): end-to-end signalling between terminals, consisting of Control, which
causes a state change in the receiver, and Indication which provides for information as to the state or
functioning of the system (see also ETS 300 144 [7] for additional information and abbreviations).
Data: refer to any of these: Low Speed Data (LSD), High Speed Data (HSD), Multi Layer Protocol (MLP),
High Speed Multi Layer Protocol (H-MLP) as defined in ETS 300 144 [7].
I-channel: the initial or only B-channel as defined in ETS 300 144 [7].
In-band signalling: signalling via the Bit-rate Allocation Signal (BAS) of the frame structure, as defined in
ETS 300 144 [7].
Lip synchronisation: operation to provide the feeling that speaking motion of the displayed person is
synchronised with his speech.
Man-machine interface: interface between human user and terminal/system, consisting of a physical
section (electro-acoustic, electro-optic transducer, keys, etc.) and a logical section dealing with functional
operation states.
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ETS 300 145: May 1994
4 Symbols and abbreviations
For the purposes of this ETS, the following symbols and abbreviations apply.
BAS Bit-rate Allocation Signal
C&I Control and Indication
CCITT The International Telegraph and Telephone Consultative Committee
CONNECT D-channel message (as in ETS 300 102-1 [2])
ECS Encryption Control Signal
ETS European Telecommunication Standard
ETSI European Telecommunications Standards Institute
FAS Frame Alignment Signal
H-MLP High Speed Multi Layer Protocol
HOLD Supplementary service
HSD High Speed Data
ISDN Integrated Services Digital Network
ITU-TS International Telecommunications - Telecommunications Standardization Sector
LSD Low Speed Data
MCU Multipoint Control Unit
MLP Multi Layer Protocol
MSB Most Significant Bit
PSTN Public Switched Telephone Network
SC Service Channel
TEA Terminal Equipment Alarm
TERM1, TERM2,
TERM3 Terminals
5 System description
For a videotelephone as described in this ETS, at most, 2 B-channels are available at a time, because it
has to be connected to an ISDN basic access conforming to ETS 300 012 [1], ETS 300 102-1 [2] and ETS
300 125 [4].
5.1 Block diagram and identification of elements (informative)
A generic videotelephony system is shown in figure 1. It consists of the videotelephone terminal, network,
Multipoint Control Unit (MCU) and other system operation entities.
A configuration of a complete videotelephone consisting of several functional units is also shown in figure
1.
- Video I/O equipment includes camera(s) and monitor(s), and video processing units to provide
functions such as split-screen scheme.
- Audio I/O equipment includes the handset and/or microphone(s), loud-speaker(s) and/or
earphone(s), and audio processing units to provide such functions as acoustic echo cancellation.
- Telematic equipment includes visual aids such as an electronic blackboard and a still picture
transceiver to enhance basic videotelephone communication as defined in CCITT T.120 series of
Recommendations: these are optional.
- The system control unit carries out such functions as network access through end-to-network
signalling, end-to-end C&I to establish a suitable mode of operation and signalling for proper
operation of the terminal through end-to-end and end-to-network signalling.
- The video codec carries out redundancy reduction coding and decoding for video signals: the
algorithm is defined in ITU-T Recommendation H.261 [5].
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ETS 300 145: May 1994
Video I/O
Video Codec
Equipment
Audio I/O
Audio Codec Delay
E quipm ent
Telematic Equipment
End-to-end Signalling
System MCU
Control
User-to-network Signalling
Figure 1: Visual telephone system
- The audio codec carries out redundancy reduction coding and decoding for audio signals: the
algorithms are defined in CCITT Recommendations G.711 [11], G.722 [12] and G.728 [14]. The
audio characteristics are defined in I-ETS 300 302 Parts 1 to 6.
NOTE 1: Parts 2 to 6 of this prI-ETS are still under study.
- Delay may be introduced into the audio path equal to the video codec delay, to maintain lip
synchronisation.
NOTE 2: The effect of lip synchronisation on the overall quality of a videotelephony
communication is under study.
- The Mux/dmux unit multiplexes transmitting video, audio, data and control signals into a single bit
stream and demultiplexes a received bit stream into constituent multimedia signals, as defined in
ETS 300 144 [7].
- The network interface makes the necessary adaptation between the network and the terminal
according to the user-network interface requirements, as defined in ETS 300 012 [1], ETS 300 102-
1 [2] and ETS 300 125 [4].
- End-to-end signalling is defined in ETS 300 143 [6] and ETS 300 144 [7].
- User-to-network signalling is defined in ETS 300 102-1 [2], ETS 300 125 [4], ETS 300 267 [10],
Clause 7.
5.2 Videotelephone terminal types
Table 1 lists terminal types of videotelephone. The terminal type is categorised according to the audio
communication modes and the number of B-channels with which the terminal can communicate (see
subclause 5.3.4).
For 2B categories, the terminal shall be able to operate in 1B and 2B modes. The type of remote terminal
is identified through the capability exchange defined in ETS 300 143 [6].
MUX / DM UX
Network Interface
Network
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ETS 300 145: May 1994
Table 1: Videotelephone terminal type
1B 2B
Type: Xa Xb1 Xb2/3 Xb4 Xb5
Mode transfer audio G.728 G.728 G.728
rate coding G.722 G.722
G.711 G.711 G.711 G.711 G.711
a0 1B G.711
♦♦ ♦♦ ♦
a1 1B G.728
♦♦ ♦
b1 2B G.711
♦♦ ♦♦
b2 2B G.722
♦♦
b3 2B G.728
♦♦
NOTE: "♦" indicates operable mode.
5.3 Signal structure and procedures
5.3.1 Frame structure
The terminal shall conform to ETS 300 144 [7].
5.3.2 Control and Indication (C&I)
C&I shall be chosen from the general audiovisual set contained in ETS 300 144 [7]. For videotelephone
systems, relevant values are listed in table 2 giving their source, sink, synchronisation with picture,
transmission channel and reference for code word definition. They are mandatory where so indicated.
All videotelephone terminals have a video source providing a picture of participants, and some terminals
may have optional additional video sources: the participant-picture source is designated #1, having the
associated symbol VIA. When incoming video is ON (BAS command (010)[1] or (010)[2]) and VIA, VIA2,
VIA3 have not been transmitted, source #1 is assumed.
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ETS 300 145: May 1994
Table 2: C&I signals for videotelephone
C&I signal Source Sink Sync. Transmission Code word Mandat-
with channel definition ory (see
picture NOTES)
C/I RX TX
(1) (1)
Picture format I decoder coder no BAS ETS 300 144 M
Picture format C coder decoder yes embedded in ITU-T MM
video Recom-
mendation
H.261
Video minimum decodable I decoder coder no BAS ETS 300 144 M
picture interval
freeze picture request C coder or decoder no BAS ETS 300 144 M
control, VCF MCU
fast update request C decoder coder no BAS ETS 300 144 M M
control, VCU or MCU (3)
freeze picture release C coder decoder yes embedded in ITU-T M
control video Recom-
mendation
H.261
MCU related C terminal terminal no MLP CCITT T.120
message or MCU or MCU series
MCU multipoint command C MCU, terminal no BAS ETS 300 144 M
conference/cancel, etc.
MCC/cancel-MCC
multipoint command C MCU terminal no BAS ETS 300 144 M
symmetrical data (4)
transmission, MCS,
and MCN
MIZ and MIS C MCU terminal no BAS ETS 300 144 M
audio loop request C terminal terminal no BAS ETS 300 144
control, LCA (1)
Mainte- video loop request C terminal terminal no BAS ETS 300 144
nance control, LCV (1)
digital loop request C terminal terminal no BAS ETS 300 144 M
control, LCD (1) (2)
loop off request, LCO C terminal terminal no BAS ETS 300 144 M
(1) (2)
Confe- split-screen indication I sending receiving yes embedded in ITU-T M
rence terminal terminal video Recom- (5)
mendation
H.261
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ETS 300 145: May 1994
Table 2: C&I signals for videotelephone (concluded)
C&I signal Source Sink Sync. Transmission Code word Mandat-
with channel definition ory (see
picture NOTES)
C/I RX TX
(1) (1)
document camera I sending receiving yes embedded in ITU-T M
indication terminal terminal video Recom- (6)
mendation
H.261
Termi- audio active/muted I sending receiving no BAS ETS 300 144 M M
nal indication, AIA/AIM terminal terminal (7) (7)
video active I sending receiving no BAS ETS 300 144 M M
/suppressed terminal terminal (7) (7)
indication VIA, VIA2,
VIA3, VIS
video ready to I sending receiving no BAS ETS 300 144 M M
activate indication, terminal terminal (8) (8)
VIR
NOTE 1: RX - mandatory (or conditionally mandatory - see following NOTES) to recognise and act upon:
TX - mandatory to send when/if relevant conditions occur.
NOTE 2: Maintenance terminals only.
NOTE 3: Mandatory if the terminal cannot decode high or low video rates - see subclause 6.2.4.1.
NOTE 4: Mandatory for a terminal which can transmit LSD, MLP, HSD or H-MLP. Terminals not obeying
MCS shall not be able to exchange video in a multipoint call when other terminals are using their
data capability.
NOTE 5: Mandatory for a terminal which can transmit a split-screen picture to CCITT Recommendation
H.100 [15].
NOTE 6: Mandatory for a terminal which has a document camera.
NOTE 7: Mandatory for a terminal which has user controls to mute audio or cut the video without also
switching off the audio/video channel within the transmitted frame.
NOTE 8: Mandatory if the terminal itself does not turn video on until it receives this code from the remote
terminal. See subclause 6.2.4.2.
5.3.3 Inband signalling procedures
The terminal shall conform to ETS 300 143 [6] for point-to-point communications.
5.3.4 Communication modes of videotelephones
Communication modes of a videotelephone for the ISDN basic access are defined according to their
channel configuration and coding. All videotelephones to this ETS shall be capable of operation in mode A
O one or more of the modes a1, b1, b2, b3.
The following modes of operation are defined for an ISDN basic interface (see also table 3):
Mode a : Mode 0U: 64 kbit/s audio to CCITT Recommendation G.711 [11], A or μ-law.
Mode 0F: 56 kbit/s audio to CCITT Recommendation G.711 [11], A or μ-law:
6,4 kbit/s video to ITU-T Recommendation H.261 [5] may, or may not, be
activated.
Mode a 16 kbit/s audio to CCITT Recommendation G.728 [14] and 46,4 kbit/s video to
1:
ITU-T Recommendation H.261 [5].
Mode b : 56 kbit/s audio to CCITT Recommendation G.711 [11] A or μ- law and 68,8
kbit/s video to ITU-T Recommendation H.261 [5].
Mode b : 48 or 56 kbit/s audio to CCITT Recommendation G.722 [12] and 76,8 kbit/s or
68,8 kbit/s video to ITU-T Recommendation H.261 [5].
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ETS 300 145: May 1994
Mode b : 16 kbit/s audio to CCITT Recommendation G.728 [14] and 108,8 kbit/s video to
ITU-T Recommendation H.261 [5].
Table 3: Communication modes of videotelephone
Videotelephone Channel rate ISDN channel Audio coding Video to ITU-T
mode Recommendation
H.261
a0 64 kbit/s B G.711 optional, on/off
a1 G.728
b1 G.711 ON
b2 128 kbit/s 2B (NOTE) G.722
b3 G.728
NOTE: In the case of two B-channels, the channels shall be synchronised according to
ETS 300 143 [6].
6 Terminal procedures
The provision of the communication is made in the following steps:
- phase A: call set-up of initial channel, D-channel signalling (subclause 6.1.1);
- phase B: mode initialisation on initial channel, inband signalling (subclause 6.1.2);
- ph
...