cx25870 Conexant Systems, Inc., cx25870 Datasheet - Page 281

• Manufacturer Part Number: cx25870
• Description: Video Encoder With Adaptive Flicker Filtering And Hdtv Output
• Manufacturer: Conexant Systems, Inc.

CX25870/871
Flicker-Free Video Encoder with Ultrascale Technology
NOTE(S):
1. The CX25870/871’s MCOMPU register must contain a value of 45 hex prior to performing a color space conversion from digital
2. Digital Pb and Digital Pr are expressed as P’B and P’R in the SMPTE specifications.
100381B
RGB to analog YPBPR. The CX25870/871’s MCOMPV register must contain a value of 51 hex prior to performing a color space
conversion from digital RGB to analog YPBPR.
E.10 Color Space Conversion Functionality to
Support Analog RGB or YP
Outputs
The CX25870/871 has the ability to receive a digital RGB stream prevalent in
graphics controllers or chipsets with integrated graphics with a width of 15/16/or
24-bits per pixel and transform it to a set of HDTV-compatible analog YP
component video outputs.
available as well. In this case, the CX25870/871 would output a set of
HDTV-compatible analog RGB component video outputs based on the same
15/16/or 24-bits per pixel RGB digital input.
color-difference digital YP
video outputs seamlessly. No color space conversion nor register reprogramming
is necessary for this case.
different from the standard digital 4:2:2 YCrCb (i.e., CCIR601) stream found
within consumer applications such as set-top boxes. As a result, the
CX25870/871 must be reprogrammed to new register values not found in
Table E-1
complete register set, contact your local Conexant Field Applications Engineer.
Once obtained, program up the CX25870 as specified and it will provide analog
YP
resulting outputs will be of high quality and viewable on SMPTE274M and
SMPTE 296M standard HDTVs.
YP
equations for conversion into digital Pb and digital Pr are listed below:
either color-difference digital YPrPb or 4:2:2 YCrCb MPEG2 input data. The
encoder will not perform this color space conversion whatsoever. For analog RGB
component HD out, a digital RGB input stream must be sent by the data master.
B
R
The option of not converting the digital RGB stream to analog YP
The CX25870/871 can support the conversion from the HDTV
However, the HDTV color-difference digital YP
For design simplicity, Conexant recommends the data master just send digital
Finally, the CX25870/871 cannot provide analog RGB video outputs from
P
P
R
B
Pb = {0.5 / (1 – 0.0722)} (B’ – Y’)
Pr = {0.5 / (1 – 0.2126)} (R’ – Y’)
video outputs based on standard 4:2:2 YCrCb MPEG2 input data. The
for consumer applications instead of YCrCb. For reference these matrix
Where (B’ – Y’) = Cb
Where (R’ – Y’) = Cr
to accommodate for the differences in the two formats. For this
Conexant
E.10 Color Space Conversion Functionality to Support Analog RGB
B
P
R
color space directly to analog YP
B
P
R
Component Video
Appendix E HDTV Output Mode
B
P
R
color space is slightly
B
P
R
component
B
P
R
B
is
P
R
E-17