參數(shù)資料
型號: ADV7183A
廠商: Analog Devices, Inc.
英文描述: Multiformat SDTV Video Decoder
中文描述: 標清多格式視頻解碼器
文件頁數(shù): 32/104頁
文件大小: 894K
代理商: ADV7183A
ADV7183A
CSFM[2:0] C Shaping Filter Mode (SDP), Address 0x17, [7]
The C shaping filter mode bits allow the user to select from a
range of low-pass filters for the chrominance signal. When
switched in automatic mode, the widest filter is selected based
on the video standard/format and user choice (see settings 000
and 001 in Table 63).
Table 63. CSFM Function
CSFM[2:0]
Description
000*
Autoselect 1.5 MHz bandwidth
001
Autoselect 2.17 MHz bandwidth
010
SH1
011
SH2
100
SH3
101
SH4
110
SH5
111
Wideband Mode
*Default value.
Rev. A | Page 32 of 104
0
–10
–20
–30
–40
–50
–60
0
5
4
3
2
1
6
0
FREQUENCY (MHz)
v740a COMBINED C RESAMPLER
A
Figure 16. SDP Chroma Shaping Filter Responses
Figure 16 shows the responses of SH1 (narrowest) to SH5
(widest) in addition to the wideband mode (in red).
SDP GAIN OPERATION
The gain control within the ADV7183A is done on a purely
digital basis. The input ADCs support a 10-bit range, mapped
into a 1.6 V analog voltage range. Gain correction takes place
after the digitization in the form of a digital multiplier.
There are several advantages of this architecture over the
commonly used PGA (programmable gain amplifier) before the
ADCs; among them is the fact that the gain is now completely
independent of supply, temperature, and process variations.
As shown in Figure 17, the ADV7183A can decode a video
signal as long as it fits into the ADC window. There are two
components to this: the amplitude of the input signal and the dc
level it resides on. The dc level is set by the clamping circuitry
(see the SDP Clamp Operation section).
If the amplitude of the analog video signal is too high, clipping
may occur, resulting in visual artifacts. The analog input range
of the ADC, together with the clamp level, determines the
maximum supported amplitude of the video signal.
The minimum supported amplitude of the input video is
determined by the SDP core’s ability to retrieve horizontal and
vertical timing and to lock to the color burst (if present).
There are two gain control units, one each for luma and chroma
data. Both can operate independently of each other. The chroma
unit, however, can also take its gain value from the luma path.
Several AGC modes are possible; Table 64 summarizes them.
It is possible to freeze the automatic gain control loops. This will
cause the loops to stop updating and the AGC determined gain
at the time of the freeze stays active until the loop is either
unfrozen or the gain mode of operation is changed.
The currently active gain from any of the modes can be read
back. Please refer to the description of the dual function manual
gain registers, LG[11:0] Luma Gain and CG[11:0] Chroma
Gain, in the SDP Luma Gain and SDP Chroma Gain sections.
0
ANALOG VOLTAGE
RANGE SUPPORTED BY ADC (1.6V RANGE FOR ADV7183A)
DATA
PRE
PROCESSOR
(DPP)
ADC
SDP
(GAIN SELECTION ONLY)
MAXIMUM
VOLTAGE
MINIMUM
VOLTAGE
CLAMP
LEVEL
GAIN
CONTROL
Figure 17. SDP Gain Control Overview
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