Operating modes
The HDMI link operates in one of three modes or periods: video data period, data island period and control period. Each period forms a part of a complete TV picture period (Figure 16.13). The video data periods are used to carry the pixels of an active video line. The data island periods are used to carry audio and auxiliary data packets. The control period is used when no video, audio, or auxiliary data needs to be transmitted. A control period is required between any two periods that are not control periods. An example of each period for NTSC television is shown in Figure 16.13. Video is transmitted during the active lines, audio and auxiliary (data island periods) and control data are transmitted during the vertical and horizontal blanking periods as shown.
Content protection, HDCP
Content protection capability is recommended for all HDMI compliant devices. An HDMI compliant source should protect all of the protected
audiovisual data. Amongst adequate copy protection technologies that are compatible with HDMI, HDCP is available.