G2R-14-12VDC Datasheet, PDF (13/73 Pages) Texas Instruments – Ultralow Power NTSC/PAL/SECAM Video Decoder With RObust Sync Detector

Gain Factor
Composite
Peak
Detector
Bandpass
X
Peaking
Line
Delay
−
SECAM Luma
Composite
SECAM Color
Demodulation
Cb
Color
LPF ↓ 2
Delay
+
Quadrature
Modulation
Notch
Filter
Notch
Filter
Delay
Y
Y
Contrast
Brightness ^Cb
Saturation
Adjust
Cr
Cb Cr
Burst
Accumulator
(Cb)
4-Line
Adaptive
Comb
Filter
LP
Filter
Delay
Composite
Quadrature
Modulation
Cr
Color
LPF ↓ 2
LP
Filter
Delay
Burst
Accumulator
(Cr)
Figure 2−1. Composite Processing Block Diagram
2.5 Luminance Processing
The luma component is derived from the composite signal by subtracting the remodulated chroma information. A line
delay exists in this path to compensate for the line delay in the adaptive comb filter in the color processing chain. The
luma information is then fed into the peaking circuit, which enhances the high frequency components of the signal,
thus improving sharpness.
2.6 Chrominance Processing
For NTSC/PAL formats, the color processing begins with a quadrature demodulator. The Cb/Cr signals then pass
through the gain control stage for chroma saturation adjustment. An adaptive comb filter is applied to the demodulated
signals to separate chrominance and eliminate cross-chrominance artifacts. An automatic color killer circuit is also
included in this block. The color killer suppresses the chroma processing when the color burst of the video signal is
weak or not present. The SECAM standard is similar to PAL except for the modulation of color which is FM instead
of QAM.
2−2