Dynamic color depth for HDCP over HDMI
A method for determining the color depths of the video data for a selected frame in High-bandwidth Digital Content Protection (HDCP) video data transmitted over a High Definition Multimedia Interface (HDMI), in which (a) the beginning of the selected frame is marked with a vertical synchronization (VSYNC) signal and (b) a mark in a window of opportunity (WOO) for the selected frame indicates whether or not that frame is encrypted. The method detects, for the selected frame, the length of the interval between a VSYNC signal and the location of at least one of (i) the start of the corresponding WOO and (ii) the mark indicating whether or not the selected frame is encrypted, and then determines the color depth of the video data for the selected frame based on the detected length.
1. A method of processing a video data frame in High-bandwidth Digital Content Protection (HDCP) video data transmitted over a High Definition Multimedia Interface (HDMI), in which (a) a beginning of a selected frame is marked with a vertical synchronization (VSYNC) signal and (b) a mark in a window of opportunity (WOO) for the selected frame indicates whether or not that frame is encrypted, said method comprising:
determining a color depth of the video data in the selected frame, and
adjusting a number of clock cycles to a starting location of the window of opportunity for the selected frame, based on the determined color depth.
2. The method of claim 1 in which the color depth of the video data is determined from a General Control Packet (GCP) transmitted over the HDMI.
3. The method of claim 1 in which the location of the starting point of the WOO is 512 clock cycles multiplied by the ratio of the color depth to 24.
4. The method of claim 1 further comprising adjusting a number of clock cycles to an ending point of the window of opportunity.
5. The method of claim 4 in which the location of an ending point of the WOO is 528 clock cycles multiplied by the ratio of the color depth to 24 minus 1.
6. The method of claim 1 further comprising maintaining statistics on the location of the WOO to increase the speed at which it is located.
7. The method of claim 6 further comprising maintaining histogram on the historical values of the WOO locations.