SAA7111A Datasheet, PDF (11/72 Pages) NXP Semiconductors – Enhanced Video Input Processor EVIP

Philips Semiconductors
Enhanced Video Input Processor (EVIP)
Product specification
SAA7111A
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-emphasised
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 chroma PLL and contains;
• Burst gate accumulator
• Colour identification and killer
• Comparison nominal/actual burst amplitude (PAL/NTSC
standards only)
• Loop filter chrominance gain control (PAL/NTSC
standards only)
• Loop filter chrominance PLL (only active for PAL/NTSC
standards)
• PAL/SECAM sequence detection, H/2-switch
generation
• Increment generation for DTO1 with divider to generate
stable subcarrier for non-standard signals.
The chrominance comb filter block eliminates crosstalk
between the chrominance channels in accordance with the
PAL standard requirements. For NTSC colour standards
the chrominance comb filter can be used to eliminate
crosstalk from luminance to chrominance (cross-colour)
for vertical structures. The comb filter can be switched off
if desired. The embedded line delay is also used for
SECAM recombination (cross-over switches).
The resulting signals are fed to the variable Y-delay
compensation, RGB matrix, dithering circuit and output
interface, which contains the VPO output formatter and the
output control logic (see Fig.6).
8.4 Luminance processing
The 8-bit luminance signal, a digital CVBS format or a
luminance format (S-VHS, HI8), is fed through a
switchable prefilter. High frequency components are
emphasized to compensate for loss. The following
chrominance trap filter (f₀ = 4.43 or 3.58 MHz centre
frequency selectable) eliminates most of the colour carrier
signal, therefore, it must be bypassed for S-video
(S-VHS and HI8) signals.
The high frequency components of the luminance signal
can be peaked (control for sharpness improvement via
I²C-bus) in two band-pass filters with selectable transfer
characteristic. This signal is then added to the original
(unpeaked) signal. A switchable amplifier achieves
common DC amplification, because the DC gains are
different in both chrominance trap modes. The improved
luminance signal is fed to the BCS control located in the
chrominance processing block (see Fig.7).
8.5 RGB matrix
Y, Cr and Cb data are converted after interpolation into
RGB data in accordance with CCIR-601
recommendations. The realized matrix equations consider
the digital quantization:
R = Y + 1.371 Cr
G = Y − 0.336 Cb − 0.698 Cr
B = Y + 1.732 Cb.
After dithering (noise shaping) the RGB data is fed to the
output interface within the VPO-bus output formatter.
8.6 VBI-data bypass
For a 27 MHz VBI-data bypass the offset binary CVBS
signal is upsampled behind the ADCs. Upsampling of the
CVBS signal from 13.5 to 27 MHz is possible, because the
ADCs deliver high performance at 13.5 MHz sample clock.
Suppressing of the back folded CVBS frequency
components after upsampling is achieved by an
interpolation filter (see Fig.42).
The TUF block on the digital top level performs the
upsampling and interpolation for the bypassed CVBS
signal (see Fig.6).
For bypass details see Figs 8 to 10.
8.7 VPO-bus (digital outputs)
The 16-bit VPO-bus transfers digital data from the output
interfaces to a feature box or a field memory, a digital
colour space converter (SAA7192 DCSC), a video
enhancement and digital-to-analog processor
(SAA7165 VEDA2) or a colour graphics board
(Targa-format) as a graphical user interface.
1998 May 15
11