3.1. <del> The catalog object MUST have a track ID of 0. </del> <ins> Per MoQTransport sect X.X, the catalog object MUST have a track name of "catalog". </ins> <del> Each catalog object MUST be independent of other catalog objects and MUST carry a unqiue group sequence number (see MoQTransport, Sect X.X).  The first catalog published MUST have a group sequence number of 0.  Every catalog object MUST have an object sequence number of 0 and there MUST be only one object per catalog group.  A catalog track object SHOULD be published only when the availability of tracks changes. </del> <ins> A catalog object MAY be independent of other catalog objects or it MAY represent a delta update of a prior catalog object.  The first catalog object published within a new group MUST be independent.  A catalog object SHOULD only be published only when the availability of tracks changes. </ins> <del> The format of the CATALOG object payload, as defined by MoQTransport Sect X.X, is as follows: </del> <ins> The format of the CATALOG object payload is as follows: </ins> Media format type: this MUST hold the value 0x001 (see IANA). <ins> This value MUST NOT be encrypted. </ins> Version: this MUST be the version of WMF to which the media packaging and catalog serialization conforms. <del> Track count: The number of tracks described by the catalog.  A catalog describing 0 tracks is a signal to the WMF client that the publishing session is complete. Each track is described by a track descriptor with the format: Track ID: Within WMF, track IDs are numeric integers.  Track IDs SHOULD start at 0 and SHOULD increment by 1 for each additional track.  Track IDs MUST never be reused.  If a track is published and then unpublished, it must be allocated a new track ID before it is re-published. Init payload: The init payload in a track descriptor MUST consist of a File Type Box (ftyp) followed by a Movie Box (moov).  This Movie Box (moov) consists of Movie Header Boxes (mvhd), Track Header Boxes (tkhd), Track Boxes (trak), followed by a final Movie Extends Box (mvex).  These boxes MUST NOT contain any samples and MUST have a duration of zero.  A Common Media Application Format Header CMAF meets all these requirements. </del> <ins> Parent object ID: 0 if this object represents an independent catalog or the parent object ID if this represents a delta update. Track change count: The number of track changes described by the catalog.  A catalog update describing 0 tracks, or deleting all existing tracks, SHALL be interpreted by the WMF client to mean that the publishing session is complete.  A WMF client SHOULD process all changes before making a subscription selection. Each track change is described by a track change descriptor with the format: Track name length: the length of track name field Track name: the UTF-8 encoded track name.  Within MoQTransport track names are strings.  Track names MUST never be reused.  If a track is published and then unpublished, it must be allocated a new track name before it is re-published.  A catalog MUST NOT reference itself i.e the the track name must not be "catalog". Operation: a binary flag. 1 if the track is being added and 0 if it is being deleted.  A publisher MUST NOT signal deletion of a track that has not been previously added. Change payload: depends upon the value of the operation flag.  If the operation is a 1 (add), then it SHALL hold an Initialization Header.  If the operation is 0 (delete), then it SHALL hold a Deletion Header. Init length: the length of the init payload Init payload: The init payload MUST consist of a File Type Box (ftyp) followed by a Movie Box (moov).  This Movie Box (moov) consists of Movie Header Boxes (mvhd), Track Header Boxes (tkhd), Track Boxes (trak), followed by a final Movie Extends Box (mvex). These boxes MUST NOT contain any samples and MUST have a duration of zero.  A Common Media Application Format Header CMAF meets all these requirements. Last group: holds the last MoQTransport Group sequence number published under that track name. Last object: holds the last MoQTransport Object sequence number published under that track name. </ins> 3.2.