Industry Video Teleconferencing Profile - VTC001
5.1. Video, communications and control
5.2. Control and Indication signals , 5.2.1. Call control (handshaking), 5.2.2. Frame structure, 5.2.3. Camera interface, 5.2.4. Monitor interface
The VTUs shall provide additional information which is needed for the proper functioning of the system. This additional information will contain ITU-T H.221 frame-synchronous control signals and indication signals such as freeze picture, video loopback, simple multipoint controls, etc., as specified in ITU-T H.230.
Among these C&I signals are AIM and AIA which indicate whether the remote VTU has audio muted or active. The VIS, VIA and VIR signals perform similar functions for the video stream. The loopback C&I signals are LCV (video), LCA (audio), LCD (digital) and LCO (loopback off). Note that there is no requirement in the Recommendation for the receiving VTU to display this information.
The VTUs shall interoperate with each other and the existing telecommunications system as specified in ITU-T H.242 and H.320.
The VTUs shall comply with the ITU-T H.221 frame structure for audiovisual teleservices in single or multiple channels as specified in ITU-T H.221. This requirement allows for the synchronization of multiple connections and the control of multiplexing audio, video, data, and other signals. Use of the unframed mode as per ITU-T H.221 is outside the scope of this Profile.
All systems shall support the capture of motion video and freeze frame video images using television cameras. For VTC equipment intended for use in North America that has external cameras, the electrical interfaces between the cameras and the VTU may optionally meet the NTSC (EIA-170) standard. The mechanical interface may optionally be BNC, F-type, or RCA connectors.
For VTC equipment intended for use in North America that has external video display monitors, the electrical interface between the monitors and the VTU may optionally meet the EIA-170A (NTSC) or RGB standard. The mechanical interface may optionally be BNC, F-type, or RCA connectors.