CX25870/871
1.0 Functional Description
Flicker-Free Video Encoder with Ultrascale Technology
1.3 Device Description
The CX25870 does not support the CGMS/A standard for analog PAL or
analog NTSC video systems. CGMS stands for Copy Generation Management
System whereby scan line 23 of PAL Field 1 or lines 20 and 283 of NTSC video
outputs contains a data burst which details the signal format. The burst also
specifies the aspect ratio, type of enhanced services, and subtitle location for the
TV to use during the broadcasted show.
In addition to the details about the signal format, the CGMS bits can indicate
whether a recording device can make no copies, one copy, or unlimited copies. If
no copies are allowed, the recording device will not make a copy. If a single copy
is allowed, the recording device will make one copy and change the CGMS data
to indicate that no future copies can be made from the native content.
The major reasons the CX25870 does not support the analog method of
CGMS/A are as follows:
•
No movie studio even considers the notion of allowing the user to make a
single copy. All DVDs released from the movie industry now enable the
Macrovision copy protection system so it is impossible to make any copies
of DVDs in the analog domain.
•
•
•
There are no plans for DVD content providers to allow users to make
limited copies of their intellectually copyrighted material.
Some aspects of the CGMS/A system are not pirate-proof and can be
disabled remotely.
The CGMS/A standard appears to be a vendor rather than a DVD
consortium mandate. Only a few DVD players have this feature now, and it is
expected that they will abandon this as newer versions of the Macrovision
standard are released or a tamper-proof version of CGMS exists.
1.3.36 Chrominance and Luminance Processing
Once the input data is converted to internal YUV format, the Y and UV
components are filtered and upsampled to the system clock frequency.
The luminance signal is always low-pass filtered using the upsampling filter
response illustrated in Figure 1-24. Additional peaking or reduction filters can be
enabled (see Figures 1-25, 1-26, and 1-27), using the PKFIL_SEL[1:0] register
field. The peaking filters are optimized for high bandwidth frequency response,
and optimal picture quality.
The default chrominance filter response is illustrated in Figure 1-28, but an
alternate wide bandwidth response can be selected using register bit
CHROMA_BW, as illustrated in Figure 1-29.
Figure 1-30 illustrates the SECAM pre-emphasis filter response for the
modulated chrominance signal.
100381B
Conexant
1-59
CONEXANT [ CONEXANT SYSTEMS, INC ]
