Specifications

62 Issue Date: 2004/11/05 │ CONFIDENTIAL
CL765 │ Camera Application Processor
Datasheet │ Doc. #: CLQP-DS-743
After alpha blending, the result image is displayed on output visual device
through provided output device interfaces: 80-Type LCD interface, RGB-Type
LCD interface and external TV encoder interface. The output visual device
interfaces share common physical pins of the CL765, and hence only one device
can be activated at a time.
4.13.1. Data Format of OSD Image
The CL765 provides three types of bitmap formats for OSD. They are 8bit-indexed,
4444-αRGB, and 565-RGB format. The 8bit-indexed format consists of 3-bit alpha
channel and 5-bit color index. The 5-bit color index is used to fetch color
component from Color Lookup Table (CLUT): CLUT has 32 entries of 16-bit color
component in 565-RGB format. Compare to other OSD bitmap format, 8bit-
indexed format saves required memory space for OSD image since it needs one
byte per pixel, while other format requires two bytes per pixel.
The bitmap in OSD buffer is expended to 18-bit (666-RGB) color component with
4-bit alpha channel either by CLUT or by bit expansion logic.
4.13.1.1. 8Bit-indexed Format
For 8bit-indexed format, R, G and B component of each pixel are from CLUT
entries indexed by lower 5 bits of input data. The resulting 4-bit alpha value is
made from input upper 3bits. Figure 4-18 shows the logical operation of bit
expansion by using CLUT for 8bit-indexed OSD case.
C_INDEX = bit[4:0]
R[5:0] = {CLUT[C_INDEX][15:11], CLUT[C_INDEX][15]}
G[5:0] = CLUT[C_INDEX][10:5]
B[5:0] = {CLUT[C_INDEX][4:0], CLUT[C_INDEX][4]}
b7
b6
b5
b4
b3
b2
b1
b0
8- bit index color
C_INDEX
A_INDEX
alpha
expansion
R[4:0] G[5:0] B[4:0]
R[4]R[4:0] G[5:0] B[4]B[4:0]
R[4:0] G[5:0] B[4:0]
R[4:0] G[5:0] B[4:0]
R[4:0] G[5:0] B[4:0]
0
29
30
31
16- bit to 18 - bit
expansion
a[3:0]
result 18 - bit color
CLUT(Color Lookup Table)
Figure 4-16. The Bit Expansion for 8Bit-index Color