saa4996h NXP Semiconductors, saa4996h Datasheet - Page 16

• Manufacturer Part Number: saa4996h
• Description: Motion Adaptive Colour Plus And Control Ic Macpacic For Palplus
• Manufacturer: NXP Semiconductors

Philips Semiconductors
7.7.1
In the event of incoming helper, the switchable low-pass
filter acts as an inverse shaping and bandwidth reduction
filter for the helper lines. If a distorted helper signal is
transmitted, the bandwidth can be reduced from 2.2 MHz
(0 dB) to 1.0 MHz or to 0.5 MHz ( 3 dB).
The high-pass part of the luminance processing is not
used for the helper processing.
To stabilize the transmitted helper signal against noise
disturbances, the encoder performs a companding of the
signal. In the decoder the decompanding is performed in
the AGOC block (see Fig.7).
7.8
In the event of full PALplus configuration, odd and even
field data are multiplexed to a 32 MHz data stream.
For the stand-alone MACPACIC, the processed even field
data is connected to the field memory FM1 and the odd
field data is switched to the output Y_MA. In the next field
the stored even field data is read out of the field memory
FM1 and then connected to the output of the MACPACIC.
If MultiPIP mode is selected, the luminance input data from
the ADC (Y_ADC) is switched directly to the output Y_MA.
In the bypass mode the luminance data processing is
switched off and multiplexed data is connected to the
MACPACIC output.
The clock frequency of the output data Y_MA is 32 MHz for
the MACPACIC in combination with the VERIC, or 16 MHz
for the stand-alone MACPACIC.
7.9
The digital data stream at the input of the PALplus decoder
module contains three reference lines;
The reference lines 23 and 623 are generated by the
PALplus encoder and are used to reduce the effects of any
errors that might be caused due to variations in the
transmission chain with respect to the levels of the
luminance letter box and helper signals.
1996 Oct 28
Reference line 22 consists of the black and mid grey
set-up, inserted by the colour/helper decoder
The second half of line 23 contains the black level
reference and the maximum negative reference for the
PALplus helper lines
The first half of line 623 contains reference values for
the black level and the peak white level for the main
lines.
Motion Adaptive Colour Plus And Control
IC (MACPACIC) for PALplus
Output signals
Measurements
L
UMINANCE HELPER PROCESSING
16
The content and the timing of the reference lines are
illustrated in Figs 13, 14 and 15.
7.9.1
Due to the fact that a standard ADC with a clamping level
of 16 should be inserted for CVBS and helper
analog-to-digital conversion, a black offset for the letter
box lines and a mid grey offset for the helper lines are
carried out in the colour/helper decoder. These offset
values are inserted as references in line 22 to reshift the
CVBS and helper signals in the digital domain without
errors. Therefore, a measurement of the offsets in line 22
is necessary. The average value of the real offset is
calculated from 64 samples and substacted from the
CVBS and helper signal. The CVBS and helper input
signal are illustrated in Fig.16.
7.9.2
The helper and luminance amplitude measurement
consists of averaging 64 samples each of;
Measured helper amplitude = helper maximum minus
helper zero.
Measured luminance amplitude = luminance white minus
luminance black.
Frame integration is performed with a feed back factor of
(1
the first measured value. Preset is controlled with the
preset bit transmitted via SNERT.
7.9.3
For the helper lines the noise measurement is carried out
in reference line 23 and for the letter box lines in reference
line 623. Both measurements are active in the black
reference levels of line 23 and line 623 respectively.
The processing of the noise measurement for the helper
signal and the letter box signal is performed in the same
way.
First the average value of 64 samples is calculated.
The single actual sample values are subtracted from this
average value and the sum of these absolute differences
are frame integrated. The integration factor is 1
Helper zero (MHZ).
Helper maximum (MHM).
Luminance black (MLB).
Luminance white (MLW).
K) =
L
L
MEASUREMENT
N
1
INE
INE
16
OISE MEASUREMENT IN LINE
. The frame integration part can be preset with
22
23
OFFSET REFERENCE MEASUREMENT
AND
623
AMPLITUDE REFERENCE
Preliminary specification
23
SAA4996H
AND
623
K =
1
16
.