
TMC2272A
PRODUCT SPECIFICATION
REV. 1.1.3 10/25/00
11
128 (Y')
=
258 (G)
+50 (B)
+131 (R)
dec.
102
032
083
hex
128 (U')
=
-149 (G)
+225 (B)
-76 (R)
dec
36B
0E1
3B4
hex
128l (V')
=
-188 (G)
-37 (B)
+225 (R)
dec.
344
3DB
0E1
hex
If the TMC2272A input data alignment for 8-bit GBR is:
0
G7
G6
G5
G4
G3
G2
G1
G0
0
B7
B6
B5
B4
B3
B2
B1
B0
0
R7
R6
R5
R4
R3
R2
R1
R0
0
then the output data alignment for 10-bit Y'U'V' is:
0
Y9
Y8
Y7
Y6
Y5
Y4
Y3
Y2
Y1
Y0
U9
U8
U7
U6
U5
U4
U3
U2
U1
U0
V9
V8
V7
V6
V5
V4
V3
V2
V1
V0
where the tripled U9 and V9 sign bits denote two’s complement
sign extensions. The factors of 4 in the input data format and
128 in the equations are absorbed by the internal 9-bit (factor
of 512) right-shifting of the emerging results.
At the output of the TMC2272A, invert the most signicant
bits, U9 and V9, of the chrominance components, and add 1 at
Y6 of the luminance to obtain the true CCIR Rec. 601 values.
Converting from GBR to 8-bit Full-Scale YUV
With the right coefcients and two external NOT gates, the
TMC2272A can convert video data from 8-bit full-scale (e.g.
VGA) GBR components to 8-bit full-scale YUV components.
Table 4. 8-bit component formats and
inclusive ranges:
Color Space Term
Range
Format
Y
Luminance
0-255
magnitude
U
Color difference,
Blue
128 to
-127
2’s comp
U'
U + 128
0-255
magnitude
V
Color difference, Red 128 to
-127
2’s comp
V'
V + 128
0-255
magnitude
G,B,R
Green, Blue, Red
components
0-255
magnitude
As in the previous RGB to YCBCR case, begin with the
dening equations, but without the range compensation
factors of 255/876 and 255/896:
Y =
0.5870 (G) +0.1140 (B)
+0.2990 (R)
U = -0.3313 (G)
+0.5000 (B)
-0.1687 (R)
V =
-0.4187 (G) -0.0813 (B)
+0.5000 (R)
The TMC2272A will compute Y, U, and V directly, whereas
inverting the most signicant bits of U and V, U7 and V7 will
yield U' and V', respectively. Multiplying the equations
immediately above by 512 and rounding each coefcient to
the nearest integer yields the recommended set of coef-
cients for GBR to YUV conversion.