Mapping

This section describes how the pixels carried on the HDMI link are mapped onto the native video interface for each of the supported color spaces. The IP-core supports RGB 4:4:4, YCbCr 4:4:4 and YCbCr 4:2:2. In a 4:4:4 format every pixel carries a complete set of three components. With a color depth of 8 bits per component each pixel occupies 24 bits: red, green and blue for RGB, or luma (Y) together with both chroma components (Cb and Cr) for YCbCr. RGB 4:4:4 and YCbCr 4:4:4 share an identical bit layout on the video interface; only the interpretation of the three components differs, so the same datapath handles either color space without structural changes. In YCbCr 4:2:2 the chroma is horizontally subsampled: each pixel keeps its own luma sample, but a single Cb/Cr pair is shared between two neighbouring pixels. In this mode the HDMI specification always transports the color components using 12 bits per component, with the active data MSB-aligned regardless of the source color depth. The pixels are processed in parallel on every clock cycle. The IP-core can be configured for dual pixels per clock (2 PPC) or quad pixels per clock (4 PPC). On each clock cycle the interface transports 2 or 4 consecutive pixels of a video line. The figures below show how the pixels and their components are distributed across the interface for each configuration.