standards automatically. See the
Standard Select,
Shutdown, and Control Register section for manual pro-
gramming.
The sync processor block also detects analog copy
protection. Extracted copy protection information is
available in Status register 0x01.
Composite Automatic Gain Control (AGC)
In addition to the analog AGC that optimizes the ADC
full-scale range, a digital AGC is used to more accu-
rately set the video amplitude. The Composite AGC
uses the amplitude of the sync signal to set the gain.
Adaptive Comb Filter
The MAX9526 uses a 5-line adaptive comb filter to sep-
arate luminance and chrominance components from a
single composite channel. The adaptation algorithm
does not require configuration. The adaptive comb filter
adjusts based on the relationship and content of video
data between neighboring lines. The filter automatically
adapts the comb filter structure between a 5-line filter
and a notch filter.
Chrominance Signal Demodulator
After luminance (Y) and chrominance (C) components
are separated, the Y component passes through a
delay line to compensate for the C component delay
through the demodulator. The chrominance signal path
contains an AGC before the signal demodulator. The
chrominance AGC uses the color burst amplitude to set
the gain. The chrominance is demodulated using a
subcarrier signal locked to the burst. The demodulated
chrominance signals, Cb and Cr, are lowpass filtered to
eliminate unwanted products of demodulation.
Output Formatting
Figure 4 shows the output formatting section of the
MAX9526.
Image Enhancement and Color Correction
The MAX9526 provides contrast, brightness, hue, and
saturation manual control in registers 0x05 to 0x08.
Time Base Correction
The MAX9526 provides time base correction (TBC) to
allow the decoder to properly process unstable and
nonstandard video from sources such as a VCR. The
time base correction minimizes the effect of sampling
jitter to ensure that there are a correct number of pixels
per active line.
Test Pattern Insertion
The MAX9526 automatically outputs a black screen
when there is no video at the inputs. The test pattern
can also be configured to provide a blue screen, 75%
color bars, or 100% color bars through register 0x0C.
Timing Reference Signal Insertion
and ITU-R BT.656 Encoding
The MAX9526 multiplexes the Y, Cr, and Cb signals
with an embedded timing reference signal conforming
to the ITU-R BT.656 standard.
SAV and EAV sequences are inserted into the data
stream to indicate the active video time in ITU-R BT.656
format. The output timing insertion is illustrated in
Figure 5. The SAV and EAV sequences are shown in
Table 2.
Output Timing
The output setup and hold diagram is shown in Figure 6.
Low-Power, High-Performance
NTSC/PAL Video Decoder
SYNC-LEVEL
CORRECTION
AND
SYNC EXTRACTION
SYNC PROCESSOR
AND ANALOG COPY
PROTECTION DETECT
COMPOSITE
AGC
ADAPTIVE
COMB
FILTER
LINE
DELAYS
Y-DELAY
CHROMINANCE
DEMODULATOR
Y/Cb/Cr
FILTERS
LPF
CHROMA
AGC
10
FROM
ANALOG
FRONT-END
Y
Cb
Cr
NTSC/PAL
TIMING
INFO
HORZ, VERT, FRAME
NONSTD
VIDEO
NONSTD VIDEO
Figure 3. Digital Composite Decoding Functional Diagram
MAX9526
Maxim Integrated
13