Philips Semiconductors
Product specification
9-bit video input processor
SAA7113H
handbook, full pagewidth
ANALOG INPUT
ADC
NO BLANKING ACTIVE
1
VBLK
0
<- CLAMP
GAIN ->
1
HCL
0
1
HSY
0
1
CLL
0
0
SBOT
1
1
WIPE
0
+
CLAMP
−
CLAMP
NO CLAMP
+
GAIN
−
GAIN
fast
−
GAIN
slow
+
GAIN
MGC647
WIPE = white peak level (254); SBOT = sync bottom level (1); CLL = clamp level [60 Y (128 C)];
HSY = horizontal sync pulse; HCL = horizontal clamp pulse.
Fig.8 Clamp and gain flow.
8.3
Chrominance processing
•
Luminance contrast and brightness
•
Limiting YUV to the values 1 (minimum) and 254
(maximum) to fulfil CCIR-601 requirements.
The SECAM-processing contains the following blocks:
•
Baseband ‘bell’ filters to reconstruct the amplitude and
phase equalized 0 and 90° FM signals
•
Phase demodulator and differentiator
(FM-demodulation)
•
De-emphasis filter to compensate the pre-emphasized
input signal, including frequency offset compensation
(DB or DR white carrier values are subtracted from the
signal, controlled by the SECAM switch signal).
The burst processing block provides the feedback loop of
the chrominance PLL and contains:
•
Burst gate accumulator
•
Colour identification and killer
•
Comparison nominal/actual burst amplitude (PAL/NTSC
standards only)
The 9-bit chrominance signal is fed to the multiplication
inputs of a quadrature demodulator, where two subcarrier
signals from the local oscillator DTO1 are applied
(0 and 90° phase relationship to the demodulator axis).
The frequency is dependent on the present colour
standard. The output signals of the multipliers are
low-pass filtered (four programmable characteristics) to
achieve the desired bandwidth for the colour difference
signals (PAL, NTSC) or the 0 and 90° FM signals
(SECAM).
The colour difference signals are fed to the
Brightness/Contrast/Saturation block (BCS), which
includes the following five functions:
•
AGC (automatic gain control for chrominance
PAL and NTSC)
•
Chrominance amplitude matching (different gain factors
for (R
−
Y) and (B
−
Y) to achieve CCIR-601 levels
C
R
and C
B
for all standards)
•
Chrominance saturation control
1999 Jul 01
13
PHILIPS [ NXP SEMICONDUCTORS ]
