CCITT SGXV                                  					       Document AVC-398R
Working Party XV/1                        					       November 6, 1992
Experts Group for ATM Video Coding

SOURCE:	CHAIRMAN OF THE EXPERTS GROUP FOR ATM VIDEO CODING
TITLE    :	REPORT OF THE NINTH MEETING IN IPSWICH AND LONDON 
	(27 October - 6 November 1992) - PART I
Purpose  :	Report

-----------------

Contents
			       1.	General
			       2.	Documentation
			       3.	Tape demonstration
			       4.	Review of the previous meetings
			       5.	Picture format
			       6.	Source coding
			       7.	Network aspects
			       8.	Very low bit rate videophone
			       9.	Work plan
			     10.	Joint sessions with MPEG
			     11.	Others

1. General

The ninth meeting of the Experts Group consisted of two parts; CCITT sole sessions in Ipswich and joint sessions with ISO/IEC JTC1/SC29/WG11 (MPEG) in London.  The list of participants appears at the end of this report. 

The first part was held during 28-30 October 1992 at Suffolk Grange Hotel in Ipswich, UK at the kind invitation of BT Laboratories.  At the opening session, Mr. Geoff Morrison made a welcoming address on behalf of the hosting organization.  

As to the membership of the group, it was announced that Ms Christel Verreth replaced Mr. Harald Brusewitz as Coordinating Member of Sweden.

At the end of the sessions, Chairman thanked the hosting organization for the meeting facilities provided and the excellent secretarial support.  

2. Documentation (TD-2)

For this meeting 49 AVC-numbered documents and 15 temporary documents have been made available as listed in Annex 1.

3. Tape demonstration (TD-3)

Several video tape demonstrations were given with D1 or U-matic as detailed in Annex 2 to present experimental results.  

4. Review of the previous meetings 

4.1 Experts Group meetings (AVC-317R,318R,355R)

The outcome of the previous two meetings were briefly reviewed;

	- New Jersey/Rio de Janeiro meeting in July 1992
	- Tarrytown meeting in September 1992

At the Tarrytown meeting, "profile" of MPEG-2 was discussed as recorded in Annex 4 to AVC-355R.  There was a question how H.26X be mapped onto the figure "Link between features and syntactic subset" in the Annex.  Chairman stated his understanding that H.26X is identical to MPEG-2 in the common text approach, though the approach itself is subject to confirmation of the group, and clarified that the H.261 compatibility feature is included in the current syntax.

4.2 CMTT/2 SRG (AVC-388)

Mr. Zedler presented current activities of the CMTT/2 SRG, drawing attention to their concern with the HDTV/CTV compatible (or more appropriately scalable) scheme, reference model and evaluation procedure.

The meeting considered possible interaction methods, noting that the liaison representative for CMTT/2 SRG is still in vacancy.  A conclusion was that we maintain the current method of interaction by exchanging liaison statements.

4.3 IVS Technical Session (AVC-320,357;TD-9)

This Technical Session was held in advance of the present meeting of the Experts Group at the same venue.  Out of 34 participants from CCITT, CCIR and ISO/IEC, 16 were from the Experts Group.

Mr. Dorman, organizer of the Technical Session, presented summary of the two day discussion and requested of the following actions by the Experts Group and WPXV/1;

	- to update the SGXV work plan,
	- to send liaison statements to SGXVIII, to follow the open issues identified at the IVS Technical Session as in TD-9.

5. Picture format

5.1 Applications (TD-6)

The meeting took note of TD-6, Japan contribution to WPXV/1, which lists possible applications on B-ISDN.  Implications to the audiovisual Recommendations are to be extracted.

5.2 Choice for H.26X or H.32X (AVC-377)

The choice of coding format(s) out of 

	- single format
	- multiple formats
	- flexible formats inside an agreed maximum

and a method to guarantee interregional communications have long been studied.  In the light of lacking clear application possibilities, AVC-377 proposed to make H.26X a generic coding standard and to commence when appropriate on "application profiles" which will include picture formats, bit rates and other parameters.  The meeting agreed to this proposal, recognizing that the issue is transferred to the H.32X terminal specifications.

5.3 Reflection to the video syntax

Even if specific formats are defined in a Recommendation other than H.26X, H.26X should have sufficient indications of possible formats.  Relevant sequence header information in the TM2 document was reviewed and found that currently there is no item specifying interlace/progressive.  This should be actioned at the London meeting.

6. Source coding

6.1 TM2 performance (AVC-394; AVC-365,395)

Basic performance of the TM2 was reported.  AVC-394 compared 2 Mbit/s operations of TM2 with CCIR-601 format and MPEG-1 with SIF and showed that the former is much better subjectively.  It was understood that difference is largely due to format conversion, not to coding kernels (MPEG-1 or TM2) and that it is advisable to directly encode full format rather than reducing format, coding, decoding and enlarging.

Two contributions  (AVC-365,395) reported performance of TM2 at a higher format of 1920 pels x 1024 lines.  It was requested to consider D1 demonstration at the next meeting by using the method of CMTT/2 SRG.  It was also advised that if there are any considerations particular to higher formats, they should be reflected to the Test Model.

During the discussion, there was a question on appropriate pre-processing such as down sampling.  Mr. Kosugi answered that 2/3 resolution reduction may be appropriate for 30 Mbit/s and Mr. Raychaudhuri indicated a US example of 1440x960 pels for about 20 Mbit/s.  Mr. Haskell pointed out that TM2 method of 4:2:0 chrominance subsampling may not be sufficient for vertical resolution and that progressive materials are interested in this respect.

6.2 Low delay mode

	6.2.1 Prediction

Intelligent prediction is the issue, but we have to await inputs to the joint sessions in London.

	6.2.2 Picture header for skipped pictures (AVC-362)

The issue has been whether headers of skipped pictures are sent and what syntax is appropriate if sent.  The meeting agreed to the proposal of AVC-362 to send the skipped picture headers by using a new picture type, which indicates the decoder not to take time for displaying skipped pictures, but specific code assignment is subject to coordination with other similar requirements.  

This syntax would be in addition to, not replacing, the existing possibility to have pictures with no bits other than headers allocated to them.  Though the latter method is recognised as incurring more delay in decoders, this may be irrelevant for some applications, yet remains totally in accordance with the existing syntax.

Communication with MPEG/SYSTEM sub-group is considered necessary on the impact of skipped pictures as to e.g. VBV delay consideration.  This should be actioned in the joint sessions.

	6.2.3 Selection of skipped pictures (AVC-363)

Based on the demonstration results showing no significant difference between skipping pictures in coding order and displaying order for M=2 field picture structure, the meeting supported to skip pictures in the coding order.

6.3 Cell loss resilience

	6.3.1 Spatial localization (AVC-360,361,368,386)

Spatial localization of the cell loss damage is achievable by structured packing and/or concealment.  The four contributions address the following items;

	- AAL and video syntax specifications to support the structured packing,
	- structured packing and/or concealment,
	- structured packing vs slice size reduction.

During the discussion, the following questions and comments were raised;

	- An open question is whether the structure of video is to be related to the structure of cell.  Structured packing causes penalty for all users; adjustable mechanism is preferable.
	- If the entry point is buffered with coded video data,  coding control may become complex and difficult.
	- Cell loss resilience should not be embedded in the source coding; codec must know the cell boundary.  It would make implementation and standard complex.  An opposing view is that we should include necessary elements in the video syntax so that they may be used when necessary, and experience shows implementation is not complex.
	- Structured packing for a multiplexed bit stream may be achievable by using the system level elements (packet start code, slice start code), this needs study.
	- We need some preventive measure for unavoidable cell loss, even if it takes place infrequently.  An opposing view is that if infrequent, simple cyclic intra refresh may be acceptable.

As a conclusion, the following actions are necessary;

	- study of structured packing for user multiplexed case, including system level implementation,
	- comparison between the structured and reduced slice size,
	- consideration for how ATM specific part be included in the generic coding.

	6.3.2 Temporal localization (AVC-393)

Temporal localization of cell loss damage is achievable by leaky prediction or cyclic intra refresh (picture, slice, column).  For this meeting, leaky prediction results were presented with tape demonstration.

	6.3.3 Leaky prediction

1) Coding efficiency (documents for the previous meetings; Section 5.5/AVC-355R; 
     AVC-393)

It was concluded that leaky prediction is competitive against the perfect prediction with cyclic intra refreshing.

2) Limit cycle fix (AVC-358,392)

Independent experiments showed that AVC-392 gives a solution.

3) Noisy back ground (Annex 3 to AVC-358,393)

Independent experiments showed that this is still a problem awaiting solutions.  During the discussion, the following possible solutions were suggested;

	- careful adaptive quantization, i.e. finer quantization for stationary backgrounds
	- stronger leaks for every third picture; rate control should be adapted and improved,
	- fine quantization of dc components,
	- differential coding of dc components.

4) Channel hopping (AVC-364)

Comparison of channel hopping performance among leaky prediction and three intra slice methods were demonstrated.  It was pointed out that since the experimented intra slice methods start intra coding just after the channel change, the time to obtain a complete picture takes twice what was demonstrated at worst.

5) Mandatory or optional

There was some discussion whether this leaky prediction be mandatory in the standard.  One view was that every decoder should have this functionality since only trivial additional cost (hardware, syntax) is required and that the standard should allow both perfect and leaky predictions.  Another view was that it should be optional since a cure should be found for the noisy background, and performance have not yet been verified at range of bit rates, for fade in /fade out sequences, {M=3, N=9}, HDTV at lower bit rates.

This matter is left open, awaiting more experimental results.  The issue of demarcation between mandatory and optional needs to be sorted out also in the wider context of generic standard.

	6.3.4 Spatially/frequency scalable layered coding (AVC-375,380,381)

The three contributions reported experimental results on the following;

	- comparison between two layered coding with single layered (simulcast) coding
	- use of concealment based on MPEG-1, with motion vector enhancement and prediction errors
	- use of concealment based on upsampled MPEG-1 without motion vector enhancement

The meeting discussed how the findings through these experiments be reflected to the standard.  Since there are no new syntax elements required for this type of cell loss resilience, the information should appear in informative annexes of the standard.

As to the method for cell loss generation, the current method described in the TM2 document (Section F.1.7/AVC-356) has been found to cause the actual cell loss rate to be higher than the desired value.  A complete solution is expected by the next meeting; in the mean time the number of initial shift of the register should be changed to 10000 from 100 with a note indicating that this solution is still provisional.  This should be actioned at the joint sessions in London

	6.3.5 Frequency scanning (AVC-385)

A method for experiments of resolution and SNR scalable scheme is given in AVC-385, which has already been incorporated in the revised version of TM2 (AVC-356).  It was noted that this scheme requires no modification in the source coding part, that the value of "n" is subject to experiments and that the frequency scanning gives 10% better efficiency for I-pictures and no change for P- and B-pictures.

Experiments are awaited.

	6.3.6 Use of priority (AVC-376,387)

AVC-376 gave analytical results for effectiveness of leaky prediction and prioritizing coded video linked with layered coding.  Those who have interests are suggested to get contact with the original author or Mr. Biggar.

AVC-387 gave a case study for the relation between generic source coding/decoding and transport media specific channel coding.  A particular feature of this example is that MPEG-2 decoder needs "error token bit" interface (8 pins in an implementation).  

Chairman drew attention of the members that we should identify ATM communication particular functionalities (or syntax elements) as soon as possible so that they be included in widely available chips.  Mr. Morrison noted in this respect that first chips usually need revision and if additional requirements are found in the mean time, they may be easily accommodated in the second version.  Mr. Raychaudhuri further pointed out that the third version may come after a much longer interval.

	6.3.7 Summary and additional experiments (TD-11,12)

Mr. Biggar undertook to chair a small group for summarizing the cell loss resilience study results and identify necessary syntax elements and additional experiments.  The outcome is contained in Annex 3.

Mr. Bjoentegaard undertook to chair a small group for summarizing the leaky prediction study results and identify necessary additional experiments.  The outcome is contained in Annex 4.

6.4 Compatibility

	6.4.1 Spatio-temporal weighting (AVC-367,379,382,390)

The four contributions reported experimental results on the spatio-temporal weighting for the spatially scalable scheme, showing some coding efficiency improvements.  The meeting considered possible reasons for this;

	- noise reduction similar to the effect for B-pictures,
	- effectively loop filtering higher frequencies,
	- rescuing uncovered backgrounds,

and got some suggestions for further experiments; frequency dependent weighting, adaptive quantization allocation between two layers, interlace-interlace as well as progressive-interlace cases.  The benefit of this new technique is reduced by the overhead of sending upper layer motion vectors for those compatibility coded macroblocks that take some of their prediction from the upper layer.

The meeting also considered how to standardize weighting coefficients.  Mr. Parke announced that he would submit a contribution proposing a syntax involving down loadable coefficients.

As to the additional memory bandwidth issue pointed out in AVC-367, it was suggested in the discussion to restrict the number of reference fields for B-pictures to 2 at maximum.

	6.4.2 H.261 compatibility (AVC-359,390)

The two contributions reported performance when the base layer is coded by H.261, particularly at low bit rates.  Difference of coding algorithm for the lower layer (MPEG-1, H.261) has been found insignificant.  Importance of co-locating spatial position between low/high layer pictures for down- and up-sampling was pointed out.

The meeting shortly considered whether all the H.26X encoders and decoders are required to have this embedded coding capability, but did not reach a unified view.  Further consideration is required in the context of "application profiles".

	6.4.3 Definition of upsampling filters (AVC-366)

AVC-366 raised the following questions regarding the upsampling filters which should be standardized;

	- spatial upsampling from CIF to higher formats,
	- temporal upsampling from CIF to higher formats,
	- processing over macroblock boundaries,
	- pel values outside the picture boundary,
	- multiplexing method for two layer video signals.

For the upsampling filters, a generic approach of down loading coefficient values and specifying arithmetic precision was suggested (see 6.4.1 above) to cope with a wide range of different combinations of low and high layer pictures.  Temporal repetition can be covered as a degenerate case of interpolation.  Some members expressed skepticism for this variable filter approach on the ground that upsampling filters from CIF may be limited in number.  Multipoint communication is also to be checked.

The issue of macroblock boundaries was clarified to be coming from the current description of TM2 (Section G.2.1/AVC-356).  Processing over macroblock boundaries is considered reasonable.  Pel values outside the picture boundary was provisionally set to 128.

As to the multiplexing method for two video signals of different layers, Mr. Morrison suggested to solve it by the system multiplex, noting that the MPEG-1 system has a mechanism to deal with this multiplexing.  Mr. Haskell drew attention to that MPEG-1 system assumes one buffer for multiplex stream.  Its implications should be analyzed.

Related to the multiplex, there was also discussion on pros and cons (necessary bit rates for each layer, delay, implementation) of the following schemes to achieve compatibility among terminals of different generation standards;

	- embedded compatible coding,
	- frequency scalable coding,
	- simulcast.

This system issue should be tackled by SGXV; this Experts Group and WPXV/1.  For example, simulcast may be applicable to LAN environments where bit rate is not so restrictive, while embedded coding is effective in bit saving sensitive communications such as international videoconferencing.

	6.4.4 Additional experiments (TD-12)

Mr. Parke undertook to chair a small group for summarizing the compatibility study results and identify necessary syntax elements and additional experiments.  The outcome is contained in Annex 5.  Members are particularly requested to contribute to the H.261 compatibility experiments.

6.5 Scalability (AVC-393)

AVC-393 demonstrated that leaky prediction cures the drift of lower resolution scales in the single loop frequency scalable coding.

6.6 VBR

	6.6.1 Traffic control and congestion control in B-ISDN - Rec. I.371 (AVC-321)

Recommendation I.371 to be approved in March 1993 contains

	- specifications for traffic description and parameters; definition of peak cell rate, etc.
	- functions and procedures for traffic control and congestion control; UPC/NPC, priority control and selective cell discard, etc.

	6.6.2 Traffic shaping (AVC-372,389; TD-13)

AVC-372 reported hardware experimental results on the necessary size of leaky bucket to obtain constant picture quality and low delay.  As far as the two experimented sequences are concerned, an order of 30 seconds is required for the former, while an order of 0.1 second can be sufficient for the latter.  

The meeting decided to send this information to SGXVIII as part of the liaison agreed at the New Jersey meeting (Section 6.5.2/AVC-317R) which describes our strong concern with time constant of the UPC characteristics for the average rate.  Mr. Yano undertook to draft this liaison statement as contained in Annex 6, noting that the used UPC mechanism is leaky bucket (not sliding window), and requesting SGXVIII's response to the possibility of measurement over a period of 10 seconds or more.

AVC-389 provided information on a traffic shaping method using mean bit rate, peak bit rate, time scale during which bit rate is constant and factor for bit rate change.  This method allows the network to make a source model and accommodate a larger number of VBR sources.  The contribution reported results for two different time scales.

7. Network aspects

7.1 B-ISDN service aspects - Rec. I.211 (AVC-322)

Recommendation I.211 to be revised next March contains service classification, general description of network aspects, and video services and coding aspect.

7.2 Video clock recovery (AVC-371,378)

Based on the previous agreement that for high quality applications video sampling clock frequency of the encoder should be conveyed to the decoder, several methods were compared in performance and adaptability to various environments.

The meeting reached a common view that this functionality should not be included in the ATM specific part.

AVC-371 proposed usage of common B-ISDN network clock while AVC-378 suggested the use of MPEG-1 system functionality comprising time stamps and buffer fill information.  A previous contribution AVC-315 reported an implementation example for the AVC-371 approach.  A concern was expressed to the MPEG-1 system method that the system need always be supported, not allowing the use of video bitstream only.

Since the common usage of the high quality network clock at both ends provides good jitter performance, there will be a possibility to combine the two approaches for B-ISDN applications.  Further elaboration is requested.

7.3 Multimedia multiplex

	7.3.1 Comparison of alternative solutions for H.22X (AVC-370,373; AVC-396)

AVC-373 provided a discussion material for multimedia multiplexing methods in integrated audiovisual terminals, taking MPEG-1 system as a possible multiplexing structure.  It also addressed demarcation between generic part and media/application dependent part in the total system.  Mr. Morrison and Mr. Haskell gave some answers to questions listed in Section 3 of this contribution regarding the MPEG system for multiplex and synchronization (see also AVC-396) including a fact that it may not conflict with the VC multiplex in B-ISDN.  It was also clarified that registration and management of stream-ids had been recognized at the Rio meeting.  In our case, several additional stream-ids would be required for terminal-to-terminal negotiation, auxiliary data transmission, etc.

The issue is whether a common multiplex method can be used across different applications such as conversational, storage and retrieval, distributive services.  Since multiplexing and demultiplexing is usually implemented with software, transcoding approach may possibly be practical even if different methods become necessary for different applications.

During the discussion, it was recognized that the user multiplex method for the B-ISDN terminals may have two alternatives; H.221 like bit oriented multiplex and MPEG system like packet (byte) oriented multiplex.  This should be studied and clarified in this group as well as in WPXV/1.

It was also recognized that bit error correction need more attention.  One thought is that bit error characteristics are transport or storage media dependent, thus it should be included in ATM specific part in our H.32X terminal case.

AVC-373 gave a revised table for comparison of multimedia multiplex alternatives.  It was pointed out that "User multiplex" should be split into two possible solutions, H.221 based and MPEG system based, reflecting the above discussion.  Mr. Biggar and Mr. Tanaka undertook to further update this table for inclusion in the IVS Baseline document.  The draft will be circulated among members for review, further improvements are welcome in this process.  A liaison statement to SGXVIII for this purpose will be finalized by mid December.

	7.3.2 Hierarchical capability solution (AVC-383)

This contribution provided a hierarchical approach for multimedia multiplex; to define several classes.  The meeting confirmed our previous decision that the support of H.320 terminal emulation is essential for H.32X terminals.

7.4 AAL

	7.4.1 AAL Type 1 - Rec. I.363 (AVC-319)

Recommendation I.363 to be revised next march gives specifications of AAL Type 1 amongst others.  The content was presented at the Stockholm meeting.

	7.4.2 AAL Type 2 (AVC-369)

This contribution provided a discussion material for two AAL Type 2 alternative solutions for video support and listed study items for the choice.  There was a comment to "demerit" in Table 1 that use of video stuffing can solve the cell assembly delay.  Buffer regulation problem in VBR video transmission was also recalled (see AVC-56).  Further digestion and elaboration are requested toward concluding a preferred AAL for video support.

	7.4.3 AAL Type 5 (AVC-397)

This new type of AAL has been developed for data applications, but it may be applicable to our audiovisual communication purposes.

7.5 Support of H.320 terminals on B-ISDN (TD-4)

The meeting agreed to send a liaison statement to SGXVIII on the subject matter as contained in Annex 7.

8. Very low bit rate videophone (AVC-384,391; TD-7,8,14)

AVC-384 demonstrated performance of H.261 like algorithm at 8 and 16 kbit/s, suggesting that the necessary modification should carefully count on the effect of image quality.  AVC-391 provided information on an implementation of the very low bit rate videophone.

Based on the discussion in the previous two meetings and information made available this time, the meeting agreed to make the following reply to WPXV/1;

	- to report the discussion as recorded in TD-8,
	- to propose the establishment of a new experts group dedicated to this study item, which cover the short term work and preparation for the long term work.

Mr. Eude undertook to draft terms of reference of and some suggestions for this experts group.  The meeting reviewed this draft and approved its revision as contained in Annex 8.

9. Work plan (AVC-320,357,374; TD-5)

Mr. Biggar advised in TD-5 that the Experts Group should establish firm objectives so we could know what Recommendations we would be producing.  AVC-374 further suggested that the group identify 

	- design component,
	- its options,
	- input required,
	- impacts,

to produce detailed work program and to align them with those of SGXVIII and SGXI.  The meeting at large and a small group of volunteers discussed how we can make our work more productive.

We have been concentrating so far on achieving a generic video coding standard H.26X aligning with MPEG-2 according to the decision at the first meeting of the group in November 1990.  Most of our efforts have been to incorporate functionalities of our concern (such as low delay, cell loss resilience, H.261 compatibility) from the audiovisual communication system point of view.  A difficulty is in the discrepancy between the freezing time of specifications (March 1993) and the time when B-ISDN network services will be made available for our applications (1995 or beyond?), but this way of working is generally considered right and profitable to CCITT.

Chairman sought the support of the group to take the common text approach for H.26X|MPEG-2.  Due to the time discrepancy mentioned above, there may happen a situation that new unknown requirements are found after the specification freezing time.  This should be taken into account and necessary procedures for adding new specifications in the future should be checked against CCITT and ISO/IEC rules.  With this proviso, the meeting supported the common text approach, subject to confirmation of Working Party XV/1.  Desire of MPEG to seek the common text approach with CCITT should also be confirmed.  

During the discussion, Mr. Parke raised a question whether we could reach the point of freezing specifications next March if the volume of experimental works required are taken into account.  It is pointed out that the MPEG resolution at Angra dos Reis includes "the requirements in WG11 N0233 have to be met in March 1993, if not the WD cannot be frozen".

We recognize that the generic coding approach leaves many system issues to the terminal Recommendation H.32X.  To make a complete interworkable system, we need standards for multimedia multiplex (H.22X), communication procedures (H.24X), call control (AV42X) and whole terminal (H.32X).  Though strictly speaking these are not under responsibility of the Experts Group, this group is an only body in WPXV/1 working for B-ISDN audiovisual systems, thus wishes to contribute to the progress.  We should draw attention of Working Party XV/1 to this situation.  In this sense, the suggestion in AVC-374 is helpful and should be implemented.

Chairman will draft a list of open issues after the meeting for review of the members, which will include priorities in terms of time schedule, missing information and linkage with applications.

The following advice was also given to improve the group productivity;

	- Currently contributions are based on interests of the members, thus tend to diverge to many topics.  Prioritizing the issues will make our work more convergent.  Prioritizing applications will be useful.
	- If prioritizing applications is difficult, case studies for typical applications will help us.
	- Assigning a specific task to a specific person or task force.
	- Exchange of opinions through correspondence during the interval of two meetings.   However, there was some concern of adjusting with regional coordination.
	- Adaptation (or extension) of existing H.320 terminals to ATM environments may be a work item of the group.

10. Joint sessions with MPEG

10.1 Documents

The following documents are put forward to the joint sessions (documents on the clock recovery will be submitted after a firm conclusion is obtained);

  - Information/discussion: 

	AVC-357,358,359,360,361,363,364,365,366,367,368,370,375,379,380,381,382, 
	          384,385,390,391,392,393,395
	TD-10,11,12

  - Proposal: AVC-362

10.2 Representatives

	CCITT EG			S. Okubo, G. Morrison
	Requirements 		S. Okubo
	Video				G. Bjoentegaard
	System			B. Haskell
	Implementation		G. Morrison

11. Others

11.1 Progress report to WPXV/1 (TD-8)

Incorporating the outcome of this meeting, revision of TD-8 is sent to WPXV/1 which will meet during 5-10 November in Geneva.  The following items are listed for particular consideration of WPXV/1;

	1) Work plan for broadband audiovisual Recommendations,
	2) Common text approach for H.26X|MPEG-2,
	3) Very low bit rate videophone activities.

11.2 Future meetings

					   Sole sessions	      Joint sessions
	January 1993 in Italy		   21-22 January	      25-29 January
	March/April 1993 in Australia   5-7 April (Melbourne)   29 March - 2 April (Sydney)

END
*    *    *

Annexes
    Annex 1	Documentation
    Annex 2	List of tape demonstrations
    Annex 3	ATM cell loss resilience framework
    Annex 4	Potential with the use of leaky prediction
    Annex 5	H.261 compatibility
    Annex 6	Liaison statement to SGXVIII on VBR video coding advantage vs UPC time 
		constant
    Annex 7	Response to the liaison from SGXVIII on support of H.320 terminals in B-ISDN
    Annex 8	Proposed terms of reference of Experts Group for Very Low Bitrate Visual 		Telephony

Participants of the ninth meeting of
Experts Group for ATM Video Coding 
(27 October - 6 November 1992, Ipswich and London)

									I    L

FRG		Mr. F. May		Daimler-Benz		X	CM
		Mr. G. Zedler		DBP Telekom		X	CM

Australia	Mr. M. Biggar	Telecom Australia		X  X	CM
		Mr. D. Dorman	Telecom Australia		X

Belgium	Mr. O. Poncin	Belgacom			X X	CM

Korea		Mr. J-Y. Nam    	ETRI                		X  X	CM

USA		Mr. V. Eyuboglu	Motorola			X
		Mr. B.G. Haskell	AT&T Bell Labs		X  X
		Mr. D. Klenke      	CLI				X  X
		Mr. J. Normile	Apple Computer		X
		Mr. N. Randall	DIS				X  X	(CM)
		Mr. D. Raychaudhuri	David Sarnoff		X
		Mr. A. Tabatabai	Tektronix			X  X	CM
		Mr. Z. Yuan  		PictureTel          		X

France 	Mr. G. Eude		CNET				X  X
		Mr. J. Guichard	CNET				     X 	CM

Italy		Ms. L. Conte		CSELT			X  X	CM

Japan		Mr. K. Hibi		Sharp				X  X
		Mr. Y. Kato		Mitsubishi			X  X
		Mr. J. Kimura	Hitachi			X  X
		Mr. Y. Kosugi	Tokyo Electric Power Co.	X  X
		Mr. S. Okubo		NTT				X  X	Chairman
		Mr. T. Tanaka	NTT				X  X	CM
		Mr. H. Ueno		Toshiba			X  X
		Mr. M. Wada		KDD				X	CM
		Mr. M. Yano		NEC				X  X
		Mr. T. Yukitake	Matsushita Communication	     X

Norway	Mr. G. Bjoentegaard 	NTR				X  X	(CM)

Netherlands	Mr. D.A. Schinkel	PTT Research   		X	CM
		Mr. A. Koster		PTT Research		     X

UK      	Mr. D. Beaumont	BT				X
		Mr. N. Kenyon	BT				X  X
		Mr. D.G. Morrison	BT				X  X	CM
		Mr. I. Parke		BT				X  X

Sweden	Ms. C. Verreth	Telia Research		X  X	CM

							  CM: Coordinating Member
							(CM): Substitute for CM