Philips Semiconductors
Product specification
Digital video encoder
7.1.2
P
ARAMETERS OF THE FADER
7.3
7.3.1
Encoder
SAA7128H; SAA7129H
Basically, there are three independent fade factors
available, allowing for the equation:
Output
=
(
FADEx
×
ln1
)
+
[ (
1
–
FADEx
) ×
ln2
]
Where x = 1, 2 or 3
Factor FADE1 is effective, when a colour in the data
stream fed to the MPEG port fader input is recognized as
being between KEY1L and KEY1U. That means, the
colour is not identified by a single numeric value, but an
upper and lower threshold in a 24-bit YUV colour space
can be defined. FADE1 = 00H results in 100% signal at the
MPEG port fader input and 0% signal at the fader Video
port input. Variation of 63 steps is possible up to
FADE1 = 3FH, resulting in 0% signal at the MPEG port
fader input and 100% signal at the fader Video port input.
Factor FADE2 is effective, when a colour in the data
stream fed to the MPEG port fader input is recognized as
being between KEY2L and KEY2U. FADE2 is to be seen
in conjunction with a colour that is defined by a 24-bit
internal Colour Look-Up Table (CLUT). FADE2 = 00H
results in 100% of the internally defined LUT colour and
0% signal at the fader Video port input. Variation of
63 steps is possible up to FADE2 = 3FH, resulting in 0% of
the internally defined LUT colour and 100% signal at the
fader Video port input.
Finally, factor FADE3 is effective, when a colour in the data
stream fed to the MPEG port fader input is recognized as
neither being between KEY1L and KEY1U nor being
between KEY2L and KEY2H. FADE3 = 00H results in
100% signal at the MPEG port fader input and 0% signal
at the fader Video port input. Variation of 63 steps is
possible up to FADE3 = 3FH, resulting in 0% signal at the
MPEG port fader input and 100% signal at the fader Video
port input.
Optionally, all upper and lower thresholds can be ignored,
enabling to fade signals only against the LUT colour.
If bit CFADM is set HIGH, all data at the MPEG port fader
are faded against the LUT colour, if bit CFADV is set
HIGH, all data at the Video port fader are faded against the
LUT colour.
7.2
Data manager
V
IDEO PATH
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 insertion of a fixed synchronization
pulse tip level, in accordance with standard composite
synchronization schemes, a blanking level can be set.
Other manipulations used for the macrovision anti-taping
process like additional insertion of AGC super-white
pulses (programmable in height) are supported by
SAA7128H only.
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. The transfer
characteristics of the luminance interpolation filter are
illustrated in Figs 10 and 11. Appropriate transients at
start/end of active video and for synchronization pulses
are ensured.
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. The transfer characteristics of the
chrominance interpolation filter are illustrated in
Figs 8 and 9.
The amplitude, beginning and ending of the inserted burst,
is programmable in a certain range that is 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 the respective standards.
In the data manager, alternatively to the external video
data, a pre-defined colour look-up table located in this
block can be read out in a pre-defined sequence (8 steps
per active video line), achieving a colour bar test pattern
generator without the need for an external data source.
2000 Mar 08
10
PHILIPS [ NXP SEMICONDUCTORS ]
