CH7004C Datasheet, PDF (14/51 Pages) List of Unclassifed Manufacturers – Digital PC to TV Encoder with Macrovision

CHRONTEL
CH7004C
Display Modes (continued)
output to either NTSC or PAL television formats. The CH7004 provides interpolated scaling with selectable factors
of 5:4, 1:1, 7:8, 5:6, 3:4 and 7:10 in order to support adjustable overscan or underscan operation when displayed on
a TV. This combination of factors results in a matrix of useful operating modes which are listed in detail in
Table 11.
Table 11. CH7004 Display Modes
TV Format
Standard
NTSC
NTSC
NTSC
NTSC
NTSC
NTSC
NTSC
NTSC
NTSC
NTSC
NTSC
NTSC
NTSC
Input
(active)
Resolution
640x480
640x480
640x480
800x600
800x600
800x600
640x400
640x400
640x400
720x400
720x400
512x384
512x384
Scale
Factor
1:1
7:8
5:6
5:6
3:4
7:10
5:4
1:1
7:8
5:4
1:1
5:4
1:1
Active
TV Lines
Percent (1)
Overscan
480
10%
420
(3%)
400
(8%)
500
16%
450
4%
420
(3%)
500
16%
400
(8%)
350
(19%)
500
16%
400
(8%)
480
10%
384
(11%)
Pixel
Clock
24.671
28.196
30.210
39.273
43.636
47.832
21.147
26.434
30.210
23.790
29.455
20.140
24.671
Horizontal Vertical
Total
Total
784
525
784
600
800
630
1040
630
1040
700
1064
750
840
420
840
525
840
600
945
420
936
525
800
420
784
525
PAL
640x480
5:4
600
14%
21.000
840
500
PAL
640x480
1:1
480
(8%)
26.250
840
625
PAL
640x480
5:6
400
(29%)
31.500
840
750
PAL
800x600
1:1
600
14%
29.500
944
625
PAL
800x600
5:6
500
(4%)
36.000
960
750
PAL
800x600
3:4
450
(15%)
39.000
936
836
PAL
640x400
5:4
500
(4%)
25.000
1000
500
PAL
640x400
1:1
400
(29%)
31.500
1008
625
PAL
720x400
5:4
500
(4%)
28.125
1125
500
PAL
720x400
1:1
400
(29%)
34.875
1116
625
PAL
512x384
5:4
480
(8%)
21.000
840
500
PAL
512x384
1:1
384
(35%)
26.250
840
625
(1) Note:Percent underscan is a calculated value based on average viewable lines on each TV format, assuming an average TV ovescan
of 10%. (Negative values) indicate modes which are operating in underscan.
For NTSC: 480 active lines - 10% (overscan) = 432 viewable lines (average)
For PAL: 576 active lines - 10% (overscan) = 518 viewable lines (average)
The inclusion of multiple levels of scaling for each resolution have been created to enable optimal use of the
CH7004 for different application needs. In general, underscan (modes where percent overscan is negative provides
an image that is viewable in its entirety on screen; it should be used as the default for most applications (e.g.,
viewing text screens, operating games, running productivity applications and working within Windows).
Overscanning provides an image that extends past the edges of the TV screen, exactly like normal television
programs and movies appear on TV, and is only recommended for viewing movies or video clips coming from the
computer. In addition to the above mode table, the CH7004 also support interlaced input modes, both in CCIR 656
and proprietary formats (see Display Mode Register section.)
Flicker Filter and Text Enhancement
The CH7004 integrates an advanced 2-line, 3-line, 4-line and 5-line (depending on mode) vertical deflickering filter
circuit to help eliminate the flicker associated with interlaced displays. This flicker circuit provides an adaptive filter
algorithm for implementing flicker reduction with selections of high, medium or low flicker content for both luma
and chroma channels (see register descriptions). In addition, a special text enhancement circuit incorporates
14
201-0000-024 Rev 2.1, 8/2/99