Broadcom BCM7405 - Color Keying and Color Matrix Architecture

2/24/2008 9T6WP
Preliminary Hardware Data Module BCM7405
06/29/07 Functional Description
Broadcom Corporation
Document 7405-1HDM00-R Video and Graphics Display Page 1-47
• CrY0CbY1_8888
• CbY1CrY0_8888
• CbY0CrY1_8888
• 8-bit format
-A_4
-A_2
-A_1
-P_8
• Other formats
-A_4
-A_2
-A_1
-P_4
-P_2
-P_1
-P_0
Color Keying and Color Matrix Architecture
Due to the mathematical complexity of the color matrix, this block can only handle one pixel per clock at the maximum rate.
The color keying operation is computationally simple enough to allow multiple pixels but to allow the order selection of when
color keying occurs, it has also been limited to this same one pixel per clock limit.
Color Matrix
The color matrix component allows conversion between different color schemes. To handle color conversion (between
differing formats), a 3 x 4 matrix multiplication is performed. This also allows reordering of components as preferred. For
example, an ARGB ordered data structure could be reordered to RGBA by correctly setting the matrix coefficients. Any
brightness, contrast, or hue adjustments would also be handled within this matrix. For details on the color conversion matrix,
see “Compositor” on page 1-42.
If converting from YUV to YCrCb data, the matrix can add or subtract the 128 value constant.