Rainbow Electronics AT91CAP9S250A - Manual (Page 919)

919
6264A–CAP–21-May-07
AT91CAP9S500A/AT91CAP9S250A
Figure 45-6. Three Frame Buffers Application and Memory Mapping
45.3.5 Codec Path
45.3.5.1 Color Space Conversion
Depending on user selection, this module can be bypassed so that input YCrCb stream is
directly connected to the format converter module. If the RGB input stream is selected, this mod-
ule converts RGB to YCrCb color space with the formulas given below:
An example of coefficients is given below:
frame n frame n+1 frame n+2 frame n-1 frame n+3 frame n+4
Frame Buffer 0
Frame Buffer 1
Frame Buffer 3
4:2:2 Image
Full ROI
ISI config Space
Codec Request
Codec Done
LCD
Memory Space
Y
C
r
C
b
C
0
C
1
C
2
C
3
C –
4
C –
5
C –
6
C –
7
C
8
R
G
B
×
Y
off
Cr
off
Cb
off
+ =
Y 0.257 R
⋅
0.504 G 0.098 B 16 +
⋅
+
⋅
+ =
C
r
0.439 R
⋅
0.368 G
⋅
– 0.071 B 128 +
⋅
– =
C
b
0.148 R
⋅
– 0.291 G 0.439 B 128 +
⋅
+
⋅
– = ⎩
⎪
⎨
⎪
⎧