Datasheet

AD9398
Rev. 0 | Page 11 of 44
4:4:4 TO 4:2:2 FILTER
The AD9398 contains a filter that allows it to convert a signal
from YCrCb 4:4:4 to YCrCb 4:2:2 while maintaining the
maximum accuracy and fidelity of the original signal.
Input Color Space to Output Color Space
The AD9398 can accept a wide variety of input formats and
either retain that format or convert to another. Input formats
supported are:
• 4:4:4 YCrCb 8-bit
• 4:2:2 YCrCb 8-, 10-, and 12-bit
• RGB 8-bit
Output modes supported are:
• 4:4:4 YCrCb 8-bit
• 4:2:2 YCrCb 8-, 10-, and 12-bit
• Dual 4:2:2 YCrCb 8-bit
Color Space Conversion (CSC) Matrix
The CSC matrix in the AD9398 consists of three identical
processing channels. In each channel, three input values are
multiplied by three separate coefficients. Also included are an
offset value for each row of the matrix and a scaling multiple for
all values. Each value has a 13-bit, twos complement resolution
to ensure the signal integrity is maintained. The CSC is
designed to run at speeds up to 150 MHz, supporting
resolutions up to 1080p at 60 Hz. With any-to-any color space
support, formats such as RGB, YUV, YCbCr, and others are
supported by the CSC.
The main inputs, R
IN
, G
IN
, and B
IN
come from the 8- to 12-bit
inputs from each channel. These inputs are based on the input
format detailed in
Table 10. The mapping of these inputs to the
CSC inputs is shown in
Table 8.
Table 8. CSC Port Mapping
Input Channel CSC Input Channel
R/CR R
IN
Gr/Y G
IN
B/CB BB
IN
One of the three channels is represented in
Figure 6. In each
processing channel, the three inputs are multiplied by three
separate coefficients marked a1, a2, and a3. These coefficients
are divided by 4096 to obtain nominal values ranging from
−0.9998 to +0.9998. The variable labeled a4 is used as an offset
control. The CSC_Mode setting is the same for all three
processing channels. This multiplies all coefficients and offsets
by a factor of 2
CSC_Mode
.
The functional diagram for a single channel of the CSC, as
shown in
Figure 6, is repeated for the remaining G and B
channels. The coefficients for these channels are b1, b2, b3, b4,
c1, c2, c3, and c4.
05678-006
×2
2
1
0
×
×
×
a1[12:0]
a2[12:0]
a3[12:0]
R
IN
[11:0]
G
IN
[11:0]
B
IN
[11:0]
+
×4
CSC_Mode[1:0]
a4[12:0]
R
OUT
[11:0]
+
1
4096
×
1
4096
×
1
4096
×
+
Figure 6. Single CSC Channel
A programming example and register settings for several
common conversions are listed in the
Color Space Converter
(CSC) Common Settings
section.
For a detailed functional description and more programming
examples, refer to Application Note AN-795, AD9880 Color
Space Converter User's Guide.