ADV7314KST Analog Devices Inc, ADV7314KST Datasheet - Page 53

• Manufacturer Part Number: ADV7314KST
• Manufacturer: Analog Devices Inc

Specifications of ADV7314KST

• Number Of Dac's: 6
• Adc/dac Resolution: 14b
• Screening Level: Commercial
• Package Type: LQFP
• Pin Count: 64
• Lead Free Status / RoHS Status: Compliant

SD DIGITAL NOISE REDUCTION
[Subaddress 63h, 64h, 65h]
DNR is applied to the Y data only. A filter block selects the high
frequency, low amplitude components of the incoming signal
[DNR input select]. The absolute value of the filter output is
compared to a programmable threshold value [DNR threshold
control]. There are two DNR modes available: DNR mode and
DNR sharpness mode.
In DNR mode, if the absolute value of the filter output is smaller
than the threshold, it is assumed to be noise. A programmable
amount [coring gain border, coring gain data] of this noise
signal will be subtracted from the original signal.
In DNR sharpness mode, if the absolute value of the filter out-
put is less than the programmed threshold, it is assumed to be
noise, as before. Otherwise, if the level exceeds the threshold,
now being identified as a valid signal, a fraction of the signal
[coring gain border, coring gain data] will be added to the origi-
nal signal in order to boost high frequency components and to
sharpen the video image.
In MPEG systems, it is common to process the video information
in blocks of 8 pixels
be applied to the resulting block transition areas that are known
to contain noise. Generally, the block transition area contains
two pixels. It is possible to define this area to contain four pixels
[border area].
It is also possible to compensate for variable block positioning
or differences in YCrCb pixel timing with the use of the [DNR
block offset].
REV. 0
Y DATA
Y DATA
INPUT
INPUT
16 pixels for MPEG1 systems [block size control]. DNR can
DNR MODE
DNR
SHARPNESS
MODE
NOISE
SIGNAL PATH
NOISE
SIGNAL PATH
INPUT FILTER
INPUT FILTER
Figure 47. DNR Block Diagram
MAIN SIGNAL PATH
MAIN SIGNAL PATH
BLOCK
BLOCK
< THRESHOLD ?
> THRESHOLD ?
8 pixels for MPEG2 systems, or 16 pixels
CORING GAIN BORDER
CORING GAIN BORDER
BLOCK SIZE CONTROL
OUTPUT
OUTPUT
BLOCK SIZE CONTROL
FILTER
FILTER
CORING GAIN DATA
CORING GAIN DATA
BLOCK OFFSET
BLOCK OFFSET
DNR CONTROL
BORDER AREA
DNR CONTROL
BORDER AREA
FILTER OUTPUT
FILTER OUTPUT
> THRESHOLD
< THRESHOLD
GAIN
GAIN
+
+
–
+
SUBTRACT SIGNAL
IN THRESHOLD
RANGE FROM
ORIGINAL SIGNAL
ADD SIGNAL
ABOVE THRESHOLD
RANGE FROM
ORIGINAL SIGNAL
DNR OUT
DNR OUT
–53–
The digital noise reduction registers are three 8-bit registers.
They are used to control the DNR processing.
Coring Gain Border [Address 63h, Bits 3–0]
These four bits are assigned to the gain factor applied to
border areas.
In DNR mode, the range of gain values is 0–1, in increments of
1/8. This factor is applied to the DNR filter output, which lies
below the set threshold range. The result is then subtracted
from the original signal.
In DNR sharpness mode the range of gain values is 0–0.5, in
increments of 1/16. This factor is applied to the DNR filter
output which lies above the threshold range. The result is added
to the original signal.
Coring Gain Data [Address 63h, Bits 7-4]
These four bits are assigned to the gain factor applied to the
luma data inside the MPEG pixel block.
In DNR mode the range of gain values is 0–1, in increments of
1/8. This factor is applied to the DNR filter output, which lies
below the set threshold range. The result is then subtracted
from the original signal.
In DNR sharpness mode, the range of gain values is 0–0.5, in
increments of 1/16. This factor is applied to the DNR filter
output, which lies above the threshold range. The result is added
to the original signal.
DNR Threshold [Address 64h, Bits 5–0]
These six bits are used to define the threshold value in the range
of 0 to 63. The range is an absolute value.
Border Area [Address 64h, Bit 6]
In setting this bit to a Logic 1, the block transition area can be
defined to consist of four pixels. If this bit is set to a Logic 0,
the border transition area consists of two pixels, where one pixel
refers to two clock cycles at 27 MHz.
DNR27 – DNR24 = 01H
720 485 PIXELS
(NTSC)
Figure 48. DNR Block Offset Control
Figure 49. DNR Border Area
APPLY DATA
CORING GAIN
O X X X X X X O O X X X X X X O
O X X X X X X O O X X X X X X O
O X X X X X X O O X X X X X X O
8 8 PIXEL BLOCK
APPLY BORDER
CORING GAIN
BORDER DATA
2 PIXEL
8 8 PIXEL BLOCK
ADV7314
OFFSET CAUSED
BY VARIATIONS IN
INPUT TIMING