Visible to Intel only — GUID: vgo1401281586864
Ixiasoft
Visible to Intel only — GUID: vgo1401281586864
Ixiasoft
5.1.2. Source Video Resampler
The gearbox converts data of 8, 10, 12, or 16 bits per component to 8-bit per component data based on the current color depth. The General Control Packet (GCP) conveys the color depth information.
- The phase counter must register the last pixel packing-phase (pp) of the last pixel of the last active line.
- The core then transmits the pp value to the attached sink device in the GCP for packing synchronization.
The HDMI cable may send across four different pixel encodings: RGB 4:4:4, YCbCr 4:4:4, and YCbCr 4:2:2 (as described in HDMI 1.4b Specification Section 6.5), and YCbCr 4:2:0 (as described in HDMI 2.0b Specification Section 7.1).
The higher order 8 bits of the Y samples are mapped to the 8 bits of Channel 1 and the lower order 4 bits are mapped to the lower order 4 bits of Channel 0.
The first pixel transmitted within a Video Data Period contains three components, Y0, Cb0 and Cr0. The Y0 and Cb0 components are transmitted during the first pixel period while Cr0 is transmitted during the second pixel period. This second pixel period also contains the only component for the second pixel, Y1. In this way, the link carries one Cb sample for every two pixels and one Cr sample for every two pixels. These two components (Cb and Cr) are multiplexed onto the same signal paths on the link.
The two horizontally successive 8-bit Y components are transmitted in TMDS Channels 1 and 2, in that order. The 8-bit Cb or Cr components are transmitted alternately in TMDS Channel 0, line by line.
For even lines starting with line 0:
- vid_data[47:32] always transfer the Yn+1 component
- vid_data[31:16] always transfer the Yn component
- vid_data[15:0] always transfer the Cbn component
For odd lines:
- vid_data[47:32] always transfer the Yn+1 component
- vid_data[31:16] always transfer the Yn component
- vid_data[15:0] always transfer the Crn component
The frequency of vid_clk must be halved when YCbCr 4:2:0 is used, because two pixels are fed into a single clock cycle.