ITU Telecommunication Standardization Sector     Document AVC-835
Study Group 15                                       October 1995
Experts Group for Video Coding and Systems in	
ATM and Other Network Environments

SOURCE:  Japan
TITLE:   Syntax for video frame synchronous C&I
PURPOSE: Proposal 
                  _______________________________

1. Introduction

The agreement at the Haninge meeting concerning video frame
synchronous C&I (VFS C&I) was that [1]:
 
(1) VFS C&I information is packed in PES packets, and PTS is used for
    timing the event;
(2) These PES packets are carried in the video synchronous 
    of the ITU H.222.1 type C elementary stream as specified in
    H.222.1 [2];
(3) The specification of VFS C&I is described in H.310. 

Following these agreements, a syntax for VFS C&I is proposed in this
document.

2. Proposed syntax for video frame synchronous C&I

The following are the features of the proposed syntax shown in the
next page:

* ASN.1 PER (Packed Encoding Rule) is used as in H.245 [3].
* "video freeze picture release control", "split screen indication",
  "document camera indication", and "closed caption" are currently
  defined as VFS C&Is [4]. For the C&Is which can be signified at the
  video stream level (i.e. "video freeze picture release control",
  "split screen indication", and "document camera indication" for
  H.261 and H.263 streams), the video synchronous subchannel is not
  used.
* Since the VFS C&I information is carried outside the H.245 channel,
  the usage of logicalChannelNumber may not be appropriate. In this
  case, other information may be used for specifying the stream to
  which the VFS C&I is applied. The possible substitutes are
  portNumber defined in H.245, or PID (for Transports Streams) and
  stream_id + stream_id_extension (for Program Streams) defined in
  H.222.0 and H.222.1.
* The VFS C&I information a PES packet is byte alligned by adding less
  than eight "0"s at the end of the encoded data. If this information
  is delivered in a Transport Stream (TS), the stuffing_byte field in
  the TS adaptation_field() defined in H.222.0 is used for alignment
  with the TS packets.


VideoFrameSynchronousCandIPDU        ::=SEQUENCE SIZE (1..65535) OF
{
  logicalChannelNumber               INTEGER (1..65535),
-- ==== Alternatives for the specification of elementary streams =====
-- or portNumber                     INTEGER (0..65535),
-- -------------------------------------------------------------------
-- or elementaryStream               CHOICE
--    {
--      ts-PID                       INTEGER (0..8191),
--      ps-StreamID                  SEQUENCE
--      {
--        streamID                   INTEGER (0..255),
--        streamIDExtension          INTEGER (0..255)
--      }
--    },
-- ===================================================================
  videoFrameSynchronousCommand       VideoFrameSynchronousCommand OPTIONAL,
  videoFrameSynchronousIndication    VideoFrameSynchronousIndication OPTIONAL,
  ...
}

VideoFrameSynchronousCommand         ::=SET
{
  nonStandard                        NonStandardParameter OPTIONAL,
  videoFreezePictureReleaseControl   NULL OPTIONAL,  -- not used for H.261 or H.263 streams
  closedCaption                      OCTET STRING OPTIONAL,	
  ...
}

VideoFrameSynchronousIndication      ::=SET
{
  nonStandardNonStandardParameter    OPTIONAL,
  splitScreenIndication              NULL OPTIONAL,  -- not used for H.261 or H.263 streams
  documentCameraIndication           NULL OPTIONAL,  -- not used for H.261 or H.263 streams
  ...
}

-- The following lines have been quoted from draft H.245

NonStandardParameter                 ::=SEQUENCE
{
  nonStandardIdentifier              NonStandardIdentifier,
  data                               OCTET STRING
}

NonStandardIdentifier                ::=CHOICE
{
  objectOBJECT IDENTIFIER,
  h221NonStandard                    SEQUENCE
  {
    t35CountryCode                   INTEGER (0..255),
    t35Extension                     INTEGER (0..255),
    manufacturerCode                 INTEGER (0..65535)
  }
}

END -- of ASN.1 source code

5. Conclusion

A syntax for VFS C&I has been proposed. Further discussion concerning
the following issues is necessary:

* The information used in the video frame synchronous subchannel for
  specifying the elementary stream to which the VFS C&I is applied.

* Specification of additional VFS C&Is and the detailed usage of each
  VFS command or indication.

References

[1] AVC-800R, "Report of the nineteenth experts group meeting in
    Haninge", S. Okubo, May 1995.
[2] ITU-T Draft Recommendation H.222.1, "Multimedia multiplex and
    synchronization for audiovisual communication in ATM
    environments", July 7, 1995.
[3] ITU-T Draft Recommendation H.245, "Control protocol for multimedia
    communication", July 6, 1995.
[4] AVC-725 , "C&I signals and their channels", Japan, Jan. 1995.

END