SAA7183A Philips Semiconductors, SAA7183A Datasheet - Page 12

• Manufacturer Part Number: SAA7183A
• Description: Digital Video Encoder EURO-DENC2
• Manufacturer: Philips Semiconductors

Philips Semiconductors
Encoder
V
The encoder generates out of Y, U and V baseband
signals luminance and colour subcarrier output signals,
suitable for use as CVBS or separate Y and C signals.
Luminance is modified in gain and in offset (latter
programmable in a certain range to enable different black
level set-ups). After having been inserted a fixed
synchronization level, in accordance with standard
composite synchronization schemes, and blanking level,
programmable also in a certain range to allow for
manipulations with Macrovision anti-taping, additional
insertion of AGC super-white pulses, programmable in
height, is supported.
In order to enable easy analog post filtering, luminance is
interpolated from 13.5 MHz data rate to 27 MHz data rate,
providing luminance in 10-bit resolution. This filter is also
used to define smoothed transients for synchronization
pulses and blanking period. For transfer characteristic of
the luminance interpolation filter see Figs 7 and 8.
Chrominance is modified in gain (programmable
separately for U and V), standard dependent burst is
inserted, before baseband colour signals are interpolated
from 6.75 MHz data rate to 27 MHz data rate. One of the
interpolation stages can be bypassed, thus providing a
higher colour bandwidth, which can be made use of for
Y and C output. For transfer characteristics of the
chrominance interpolation filter see Figs 5 and 6.
The amplitude of inserted burst is programmable in a
certain range, suitable for standard signals and for special
effects. Behind the succeeding quadrature modulator,
colour in 10-bit resolution is provided on subcarrier.
The numeric ratio between Y and C outputs is in
accordance with set standards.
T
Pin TTX receives a teletext bitstream sampled at the LLC
clock, each teletext bit is carried by four or three LLC
samples.
Phase variant interpolation is achieved on this bitstream in
the internal teletext encoder, providing sufficient small
phase jitter on the output text lines.
TTXRQ provides a fully programmable request signal to
the teletext source, indicating the insertion period of
bitstream at lines selectable independently for both fields.
The internal insertion window for text is set to 360 teletext
bits including clock run-in bits. For protocol and timing
see Fig.19.
1996 Oct 02
ELETEXT INSERTION AND ENCODING
IDEO PATH
Digital Video Encoder (EURO-DENC2)
12
C
Using this circuit, data in accordance with the specification
of Closed Caption or Extended Data Service, delivered by
the control interface, can be encoded (Line 21).
Two dedicated pairs of bytes (two bytes per field), each
pair preceded by run-in clocks and framing code, are
possible.
The actual line number where data is to be encoded in, can
be modified in a certain range.
Data clock frequency is in accordance with definition for
NTSC-M standard 32 times horizontal line frequency.
Data LOW at the output of the DACs corresponds to 0 IRE,
data HIGH at the output of the DACs corresponds to
approximately 50 IRE.
It is also possible to encode Closed Caption Data for 50 Hz
field frequencies at 32 times horizontal line frequency.
A
For more information contact your nearest Philips
Semiconductors sales office.
RGB processor
This block contains a dematrix in order to produce RED,
GREEN and BLUE signals to be fed to a SCART plug.
Before Y, Cb and Cr signals are de-matrixed, individual
gain adjustment for Y and colour difference signals and
2 times oversampling for luminance and 4 times
oversampling for colour difference signals is performed.
For transfer curves of luminance and colour difference
components of RGB see Figs 9 and 10.
SECAM processor
SECAM specific pre-processing is achieved in this block
by a pre-emphasis of colour difference signals (for gain
and phase see Figs 11 and 12).
A baseband frequency modulator with a reference
frequency shifted from 4.286 MHz to DC carries out
SECAM modulation in accordance with appropriate
standard or optionally wide clipping limits.
After the HF pre-emphasis, also applied on a DC reference
carrier (anti-Cloche filter; see Figs 13 and 14), line-by-line
sequential carriers with black reference of 4.25 MHz (Db)
and 4.40625 MHz (Dr) are generated using specified
values for FSC programming bytes.
Alternating phase reset in accordance with SECAM
standard is carried out automatically. During vertical
blanking the so-called bottle pulses are not provided.
NTI
LOSED CAPTION ENCODER
-
TAPING
(SAA7183A
SAA7182A; SAA7183A
ONLY
)
Preliminary specification