1.3 Overview

 The H.245 Protocol, as specified in [H245-1.3], is the control protocol for multimedia communication contained within the H.323 specification. H.323, as specified in [H323-1.2], is a protocol suite defined by the ITU and used for Voice over IP (VoIP) and video conferencing.

The Microsoft TAPI3.0 product (included in Windows 2000 operating system) implemented an H.323 endpoint following the ITU protocol specification. TAPI3.0 uses the Digital Video Interactive 4 (DVI4) audio codec, which is not one of the codecs defined in [H323-1.2]. TAPI3.0 uses the H.245 Protocol: Microsoft Extensions to include DVI4 as one of the codecs available for negotiation during call setup time.<1>

The H.323 Protocol includes the H.245 terminal capability negotiation procedure, as specified in [H323-1.2] and [H245-1.3]. Microsoft has added support to this procedure for the Digital Video Interactive 4 (DVI4) audio codec at the 16-kilohertz (kHz) sample rate. If the Abstract Syntax Notation One (ASN.1) AudioCapability message included in the H.245 negotiation procedure contains a nonStandardParameter, with nonStandardIdentifier set to the Object Identifier "{ 1 3 6 1 4 1 311 19 2 }", and data set to the Octet String "11 00 01 00 80 3E 00 00 40 1F 00 00 01 00 04 00 02 00 14 00", the 16-kHz DVI4 codec is supported.

[H245-1.3] has a capability that allows the client to change the logical channel that is rendered. The H.245 Protocol: Microsoft Extensions do not implement this functionality, as specified in section 2.2.2.

[H245-1.3] has a capability that allows the client to place a [T120] call to a dynamic transport address, instead of the standard well-known port address described in [T120]. The H.245 Protocol: Microsoft Extensions do not implement this functionality as specified in section 2.2.3.