1.0 Functional Description
CX25870/871
1.3 Device Description
Flicker-Free Video Encoder with Ultrascale Technology
1.3.39 CCIR601 Mode Operation for DVD Playback
Data coming from a DVD is decoded by a MPEG2 decoder or graphics controller
into a format called CCIR601. CCIR601 is the more common name for 4:2:2
YCrCb data at a 27 MHz pixel rate, as specified in the ITU-R BT.601 standard.
This specification was developed specifically for the digitalization of color video
signals.
To play a DVD movie on a television in addition to a CRT monitor, the
CX25870/871, a CCIR601 compatible encoder, must be integrated into the
hardware design. Actual CCIR601 data must be sent from a MPEG2 decoding
master device directly to the CX25870/871 encoder. This can be either a
dedicated MPEG2 decoder chip or a graphics controller with this functionality.
Various software steps are necessary so the encoder enters slave or master
interface and is set up to accept the interlaced YCrCb data or noninterlaced RGB
digital format. After all of these steps have been executed properly, a DVD movie
stream is properly encoded and rendered onto the television by the VGA encoder.
There are different capabilities among graphics controllers, MPEG2 decoders,
and proprietary ASICs that impact the particular DVD implementation. This
section seeks to cover all the possible hardware/software configurations and the
trade-offs associated with each. If the reader has an interface idea about the
routing of data from the CCIR601 source to encoder that is not discussed here,
please contact your local Conexant Field Applications Engineer for further
technical support.
1.3.39.1 CCIR601 Data
In/NTSC Out
The first option to playing a DVD movie via the CX25870/871 is to send the
digital video CCIR601 data directly to the encoder from the MPEG2 decoder. In
this case, the graphics controller does not have any effect on the CCIR601 digital
stream arriving at the input of the encoder because it bypassed the data or the data
was routed around the controller. In either case, the CX25870/871 must be
configured to accept interlaced 4:2:2 YCrCb data with an active resolution of
720x480 and output a standard NTSC video output. The pertinent set of
conditions for this option are:
• Type of Digital Video Input:
• Active Resolution (HorizontalxVertical):
• Overscan Compensation:
• Interface:
Interlaced 4:2:2 YCrCb
720 pixels x 480 lines
None. Horizontal = 0%; Vertical = 0%
CX25870/871 is clock and timing slave
27.000 MHz
• Pixel Rate
• Type of Analog Video Output:
Standard NTSC[NTSC-M]
Given this set of conditions, autoconfiguration mode 28 is a perfect fit for this
architectural option. As a result, simply use the MPEG2 decoders serial bus
mastering ability to program the CX25870/871s CONFIG[5:0] field with a binary
value of 011100. This translates into writing a hexadecimal number of 0x34 to
register 0xB8. Once the encoder acknowledges this write to its autoconfiguration
register, it automatically loads the appropriate value for this type of DVD
configuration into its register indices from 0x76 to 0xB4 including 0x38. The
exact data transferred into these registers is contained in Appendix C.
1-66
Conexant
100381B
CONEXANT [ CONEXANT SYSTEMS, INC ]
