This Recommendation describes terminals for low bit-rate multimedia communication, utilizing V.34 modems operating over the GSTN. H.324 terminals may carry real-time voice, data, and video, or any combination, including videotelephony.H.324 terminals may be integrated into personal computers or implemented in stand-alone devices such as videotelephones. Support for each media type (voice, data, video) is optional, but if supported, the ability to use a specified common mode of operation is required, so that all terminals supporting that media type can interwork. This Recommendation allows more than one channel of each type to be in use. Other ITU-T Recommendations in the H.324-Series include the H.223 multiplex, H.245 control, H.263 video codec, and G.723.1 audio codec.This Recommendation makes use of the logical channel signalling procedures of ITU-T Rec. H.245, in which the content of each logical channel is described when the channel is opened. Procedures are provided for expression of receiver and transmitter capabilities, so transmissions are limited to what receivers can decode, and so that receivers may request a particular desired mode from transmitters. Since the procedures of this Recommendation are also planned for use by ITU-T Rec. H.310 for ATM networks, and ITU-T Rec. H.323 for non-guaranteed bandwidth LANs, interworking with these systems should be straightforward.H.324 terminals may be used in multipoint configurations through MCUs, and may interwork with H.320 terminals on the ISDN, as well as with terminals on wireless networks.Annex A defines the data protocol stack for use with the H.324 control channel.Annex B defines HDLC frame structure transparency for asynchronous transmission.Annex C defines the use of H.324 terminals in error-prone transmission environments ("also referred to elsewhere as H.324/M").Annex D defines the use of H.324 terminals on ISDN circuits ("also referred to elsewhere as H.324/I").Annex E defines timer T401 initialization for operation over geostationary satellite channels.Annex F supports multilink operation on the GSTN and ISDN.Annex G defines the use of ISO/IEC 14496-1 ("MPEG-4 Systems") generic capabilities in H.324 terminals.Annex H supports multilink operation on error-prone mobile networks.Annex I defines the use of HTTP in H.324 terminals, enabling non-conversational services with a user interface through web-like menus. |
