Copy
Protection
Detector
VBI Data
Processor
Slice VBI Data
Y[9:0]
Output
Formatter
C[9:0]
FSS
CH1 A/D
2x
Decimation
2x
Decimation
2x
Decimation
2x
Decimation
XTAL1
XTAL2
RESETB
PWDN
DATACLK
CVBS/Y/G
CVBS/Y
Composite
Processor
YCbCr
CH2 A/D
C
CH3 A/D
Y/G
Pb/B
Pr/R
Component
Processor
YCbCr
CH4 A/D
FID
VS/VBLK
Timing
Processor
HS/CS
GLCO
AVID
Host
Interface
SCL
SDA
Figure 2−2. Digital Video Processing Block Diagram
2.2.1
2x Decimation Filter
All input signals are oversampled by a factor of 2 (27 MHz). The A/D outputs first pass through decimation filters that
reduce the data rate to 1x the pixel rate. The decimation filter is a half-band filter. Oversampling and decimation
filtering can effectively increase the overall signal-to-noise ratio by 3 dB.
2.2.2
Composite Processor
Figure 2−3 is a block diagram of the TVP5146 digital composite video processing circuit. This block receives a
digitized composite or S-video signal from the ADCs and performs Y/C separation (bypassed for S-video input),
chroma demodulation for PAL/NTSC and SECAM, and YUV signal enhancements.
The 10-bit composite video is multiplied by the subcarrier signals in the quadrature demodulator to generate color
difference signals U and V. The U and V signals are then sent to low-pass filters to achieve the desired bandwidth.
An adaptive 5-line comb filter separates UV from Y based on the unique property of color phase shifts from line to
line. The chroma is remodulated through a quadrature modulator and subtracted from line-delayed composite video
to generate luma. This form of Y/C separation is completely complementary, thus there is no loss of information.
However, in some applications, it is desirable to limit the U/V bandwidth to avoid crosstalk. In that case, notch filters
can be turned on. To accommodate some viewing preferences, a peaking filter is also available in the luma path.
Contrast, brightness, sharpness, hue, and saturation controls are programmable through the host port.
2−3
TI [ TEXAS INSTRUMENTS ]
