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VCT3801A 参数 Datasheet PDF下载

VCT3801A图片预览
型号: VCT3801A
PDF下载: 下载PDF文件 查看货源
内容描述: 视频/控制/图文电视IC系列 [Video/Controller/Teletext IC Family]
分类和应用: 电视
文件页数/大小: 172 页 / 2219 K
品牌: MICRONAS [ MICRONAS ]
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VCT 38xxA  
ADVANCE INFORMATION  
2.4.9. Luminance Notch Filter  
2.5. Horizontal Scaler  
If a composite video signal is applied, the color infor-  
mation is suppressed by a programmable notch filter.  
The position of the filter center frequency depends on  
the subcarrier frequency for PAL/NTSC. For SECAM,  
the notch is directly controlled by the chroma carrier  
frequency. This considerably reduces the cross-lumi-  
nance. The frequency responses for all three systems  
are shown in Fig. 2–9.  
The 4:2:2 YCrCb signal from the color decoder is pro-  
cessed by the horizontal scaler. The scaler block  
allows a linear or nonlinear horizontal scaling of the  
input video signal in the range of 0.25 to 4. Nonlinear  
scaling, also called “Panoramavision”, provides a geo-  
metrical distortion of the input picture. It is used to fit a  
picture with 4:3 format on a 16:9 screen by stretching  
the picture geometry at the borders. Also, the inverse  
effect can be produced by the scaler. A summary of  
scaler modes is given in Table 2–1.  
dB  
10  
The scaler contains a programmable decimation filter,  
a 1-line FIFO memory, and a programmable interpola-  
tion filter. The scaler input filter is also used for pixel  
skew correction (see Section 2.4.10. on page 16). The  
decimator/interpolator structure allows optimal use of  
the FIFO memory. The controlling of the scaler is done  
by the internal Fast Processor.  
0
–10  
–20  
–30  
–40  
MHz  
Table 2–1: Scaler modes  
0
2
4
6
8
10  
PAL/NTSC notch filter  
Mode  
Scale  
Description  
Factor  
dB  
10  
Compression 0.75  
4:3 source displayed on  
a 16:9 tube,  
4:3 16:9  
linear  
0
with side panels  
–10  
Panorama  
4:3 16:9  
non-  
linear  
compr  
4:3 source displayed on  
a 16:9 tube,  
Borders distorted  
–20  
–30  
–40  
Zoom  
4:3 4:3  
1.33  
linear  
Letterbox source (PAL+)  
displayed on a 4:3 tube,  
vertical overscan with  
cropping of side panels  
MHz  
0
2
4
6
8
10  
SECAM notch filter  
Fig. 2–9: Frequency responses of the luma  
notch filter for PAL, NTSC, SECAM  
Panorama  
4:3 4:3  
non-  
linear  
zoom  
Letterbox source (PAL+)  
displayed on a 4:3 tube,  
vertical overscan, bor-  
ders distorted, no crop-  
ping  
2.4.10.Skew Filtering  
The system clock is free-running and not locked to the  
TV line frequency. Therefore, the ADC sampling pat-  
tern is not orthogonal. The decoded YCrCb signals are  
converted to an orthogonal sampling raster by the  
skew filters, which are part of the scaler block.  
2.6. Black-line Detector  
In case of a letterbox format input video, e.g. Cinema-  
scope, PAL+ etc., black areas at the upper and lower  
part of the picture are visible. It is suitable to remove or  
reduce these areas by a vertical zoom and/or shift  
operation.  
The skew filters allow the application of a group delay  
to the input signals without introducing waveform or  
frequency response distortion.  
The VCT 38xxA supports this feature by a letterbox  
detector. The circuitry detects black video lines by  
measuring the signal amplitude during active video.  
For every field the number of black lines at the upper  
and lower part of the picture are measured, compared  
to the previous measurement and the minima are  
stored in the I2C-register BLKLIN. To adjust the picture  
The amount of phase shift of this filter is controlled by  
the horizontal PLL1. The accuracy of the filters is 1/32  
clocks for luminance and 1/4 clocks for chroma. Thus  
the 4:2:2 YCrCb data is in an orthogonal pixel format  
even in the case of nonstandard input signals such as  
VCR.  
16  
Micronas  
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