1、 - - ITU-T RECMN*H.331 93 4862593 0582584 T90 INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU LINE TRANSMISSION OF NON-TELEPHONE SIGNALS H.331 (03/93) BROADCASTING TYPE AUDIOVISUAL MULTIPOINT SYSTEMS AND TERMINAL EQUIPMENT ITU-T Recommendation H.331 (Previ
2、ously “CCITT Recommendation”) ITU-T RECMN*H.333 93 m 4862593 0582585 927 W FOREWORD The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the International Telecom- munication Union. The ITU-T is responsible for studying technical, operating and tariff questions and issuin
3、g Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Conference (WTSC), which meets every four years, established the topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on the
4、se topics. ITU-T Recommendation H.331 was prepared by the ITU-T Study Group XV (1988-1993) and was approved by the WTSC (Helsinki, March 1-12, 1993). NOTES 1 As a consequence of a reform process within the Jntemational Telecommunication Union (ITU), the CCITT ceased to exist as of 28 February 1993.
5、In its place, the ITU Telecommunication Standardization Sector (ITU-T) was created as of 1 March 1993. Similarly, in this reform process, the CCIR and the IFRB have been replaced by the Radiocommunication Sector. In order not to delay publication of this Recommendation, no change has been made in th
6、e text to references containing the acronym “CCIIT, CCIR or IFRB” or their associated entities such as Plenary Assembly, Secretariat, etc. Future editions of this Recommendation will contain the proper terminology related to the new ITU structure. 2 telecommunication administration and a recognized
7、operating agency. In this Recommendation, the expression “Administration” is used for conciseness to indicate both a Q ITU 1993 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,
8、without permission in writing from the ITU. CONTENTS 1 Scope 2 Definitions 3 System description . 4 Terminal description 4.1 Configuration 4.2 4.3 Video coder and decoder 4.1 Audio coder and decoder 4.5 Frame structure . Communication modes and terminal types . 4.6 C ainong others - reiiicite sun-ei
9、llance from multiple sites: - remote lecturing; - inforiiiation provision. The Iact t.xariiple is similar to the telephone information service provided on the conventional analog telephone network. Recommendation H.331 (03/93) 1 ITU-T RECMN*H-331 93 m 4862591 0582588 b3b I information ISDN Informati
10、on receiving terminal I RT providing Exchange terminal T1507490-92/dOl FIGURE 1M.331 System configuration for Broadcasting multipoint service 4 Terminal description 4.1 Configuration IFT and IRT configurations are similar to that of H.320 terminals, but IPT has only audiovisual signal transmitting c
11、apability while IRT has only audiovisual signal receiving capability (see Figure 2). Major difference from H.320 resides in the system control part. 4.2 As per Tables 1M.320 and 2M.320. Communication modes and terminal types 4.3 Video coder and decoder As per Recommendation H.261 or others identifie
12、d in Annex M.221. 4.4 Audio coder and decoder As per Recommendations G.7 1 1, G.722, G.728, H.200lAV253 or others identified in Annex M.221, 4.5 Frame structure As per Recommendation H.221. 4.6 C Freeze picture request control “VCF” defined in Recommendation H.230; Freeze picture release control def
13、ined in Recommendation H.261; Split screen indication defined in Recommendation H.261; Document camera indication defined in Recommendation H.261; Audio activelmuted indication “AWAIM” defined in Recommendation H.230; Video active indication “VIANIA2/VL43” defined in Recommendation H.230; Video supp
14、ressed indication “VIS” defined in Recommendation H.230. 2 Recommendation H.331 (03/93) Video Coda Video input equipment H.2/AV.25 - video standards, format (CIF/QCIF), minimum picture intervals; - transfer rates; - restricted network if relevant; - LSD, HSD, MLP, H-MLP if relevant; - applications i
15、n data channel if relevant; - multiple-byte extension if relevant. IRT should include necessary functions required by IPT according to the service specifications. After IRT has received a CONNECT message from the network through the outband channel, it searches H.221 framing in the inband channel an
16、d prepares to receive the incoming audiovisual signal including FAS and BAS from IPT through the network. The sending signal including FAS and BAS can be arbitrary. After IPT has sent a CONNECT message and received a CONNECT ACKNOWLEDGE message from the network through the outband channel, it starts
17、 to send the H.221 framed audiovisual signal together with corresponding BAS commands through the inband channel, ignoring the received signal and inserting the following bits in FAS: - A = O regardless of the received signal; - E = O regardless of the received signal; CI, C2, C3, C4 as calculated;
18、- - - LI, L2, L3 as appropriate; N1, N2, N3, N4 as appropriate in case of multiple B or multiple HO communications. IRTs except the first calling one may get access to the bitstream from IPT at an arbitrary point, thus it may be necessary for the IPT to insert INTRA pictures cyclically and for the I
19、RT to mute audiovisual signals until they become clean at the output of the, decoders. The frequency of INTRA picture insertion and the timing to release muting are left to the designers choice. 4.7.2 Exceptional procedures Recovery from fault conditions, such as loss of H.221 framing, is in general
20、 left to the designers choice. Guidance for some recoveiy procedures is for further study. 5 Call control arrangements NOTE - This clause gives an example of a multipoint broadband network capability. It is not to be interpreted as a standardized service description of a multipoint broadcast service
21、. 4 Recommendation H.331 (03/93) ITU-T RECNN*H-331 93 m 4862593 0582591 II20 m 5.1 Network conditions The network provides this broadcasting multipoint capability subject to the following conditions: - IPTs using this service are appropriately pre-registered with the network. The IPT is assigned a g
22、eneral ISDN number in case of single B or Ho channel communication. In case that multiple B or Ho channels are used, each channel is assigned an independent number. This is necessary to distinguish constituent channels with each other. If an IRT wishes to connect to the IPT, it can call that general
23、 ISDN number(s). Therefore, no special network access protocol or special access number is required in the call initiation procedure from the IRT to the network. The calling procedure from the network to the IPT is the general calling procedure. There is also no need for special protocols that allow
24、 to distinguish niulticonnection from general connection. - - 5.2 Call set-up An IRT (IRT-1) calls the IPT by using the IPTs ISDN number. When the destination exchange acconiniodating the IPT can acknowledge that the destination user is a registered IPT, the network sends a setup sigiial to the IPT
25、through the outband channel. After receiving the IPTs response, the network connects only the path from the IPT to the IRT. The path from the IRT to the IPT is not connected but terminated at the network. When the IPT connected to the IRT is called by other IRTs IRT-2, 3, . . .). the destination exc
26、hange does not send a setup signal to the IPT. This is different from the first call procedure. Then the destination exchange connects only the paths from the IPT to the IRT. So the same information is distributed to each connected IRT. 5.3 Call release When an IRT IRT-a) sends a disconnect signal,
27、the destination exchange releases the path from it to IRT-a but does not transmit this signal to the IPT. The JPT therefore doesnt know that the communication to the IRT-a has been finished. The destination exchange maintains the connection and path from the IPT to the other IRTs. When the last IRT
28、sends its disconnect signal, the destination exchange sends this signal to IPT and releases the path as it releases the path for a general call. 5.4 Multiple channels In case tif multiple R or H(, cuiiiiiiunications, the calling terminal niay place multiple calls according to the terniinal procedure
29、 - sequentially from the initial channel, confirming the received channel number contained in FAS and BAS; - siniiiltaneously. Coding rule for information elements in the call setup niessage follows that of audiovisual services defined in Recommendation Q.839. Particular setting of octet 4 of HLC fo
30、r this broadcasting type niultipoint service is for further study. 5.5 Authentication of the receiving terminals When IPT is called by an IRT? it niay be nccessary to authenticate the caller by the IPT or the network. This is for further study. 6 Intercommunication This terminal is not expected to interconimunicate with telephone terminals or visual telephone terminals defined in Recommendation H.320. Recommendation H.331 (03/93) 5
