1.0 Functional Description
CX25870/871
1.3 Device Description
Flicker-Free Video Encoder with Ultrascale Technology
This design is illustrated in Figure 1-33.
Figure 1-33. DVD Playback Utilizing Graphics Controller for Color-Space and Progressive Scan Conversion
CRT
Monitor
Subpicture
Decoder
100 kbit/s
Graphics
Accelerator
20
Mbit/s
10
Mbit/s
15
Mbit/s
CX25870/
CX25871
DVD-ROM
Drive
Host
Adapter
Stream
Parsing
MPEG-2
Decoder
NTSC or PAL
Television
Sound
Card
AC-3
Decoder
450 kbit/s
Speakers
100381_061
To enable DVD playback with this architecture, the graphics controller must
be able to deinterlace and color space convert the CCIR601 input data from the
MPEG2 decoding source. Furthermore, since the pixel clock frequency is not
27.000 MHz any longer, the graphics controller must have the ability to
synchronize the pixel data to the clock rate dictated by the CX25870/871s CLKO
signal. Finally, the controller must be able to function as the clocking master and
timing slave as described in Section 1.3.7 of this data sheet.
The recommended interface for the CX25870/871 for this option is Master
and the encoder must be programmed to accept noninterlaced RGB data and
output a standard NTSC video output. The pertinent factors for this option are:
• Type of Digital Video Input:
Progressive Scan/Noninterlaced; 24-bit RGB
per pixel Multiplexed Input Format
• Active Resolution (HorizontalxVertical):
• Overscan Compensation Ratio:
• Interface:
720x480
Minimal; Horizontal = 1.24%; Vertical = 1.23%
CX25870/871 is clock and timing master
27.6923 MHz
• Pixel Rate
• Type of Analog Video Output:
Standard NTSC[NTSC-M]
Given this set of conditions, autoconfiguration mode 44 is a perfect fit for this
architectural option. As a result, simply use the graphics accelerator’s serial bus
mastering ability to program the CX25870/871s CONFIG[5:0] field with a binary
value of 101100. This translates into writing a hexadecimal number of 0x54 to
register 0xB8. Once the encoder acknowledges this write to its autoconfiguration
register, it automatically loads the appropriate values 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.
1-68
Conexant
100381B
CONEXANT [ CONEXANT SYSTEMS, INC ]
