ch5001a ETC-unknow, ch5001a Datasheet - Page 7

• Manufacturer Part Number: ch5001a
• Description: Cmos Color Digital Video Camera
• Manufacturer: ETC-unknow

CHRONTEL
CH5001A
A/D Conversion:
The data out of the programmable sample and hold is input to an 8-bit A/D. The output of the A/D is sent to the
datapath section, and can alternatively be sent directly to the Y[7:0] pins. The A/D has an over-range output which
is available as an external pin.
Transformation to RGB domain:
Each pixel output from the A/D has been exposed to light which was filtered by one of three types of colored filter,
red, green or blue. To create RGB values for each pixel, four neighboring pixels are combined in different strengths
in a matrix multiplier. The gains used in the matrix multiplier are programmable via the CSCXX[7:0] registers.
Programmable Gamma correction of RGB signals:
The RGB signals are next applied to a gamma correction block with selectable gamma settings of 1.0, 1.6 and 2.2,
controlled via GAM[1:0]. Following gamma correction, a programmable offset is added to each term, via controls
ROS[4:0], GOS[4:0] and BOS[4:0].
Convert to the YCrCb domain:
A color space conversion is then applied to the gamma corrected RGB signals to convert to the Y, Cr, Cb domain.
The Cr and Cb gain can be independently adjusted in this block with the CRG and CBG controls.
Interpolate/Decimate data to desired resolution:
The output resolution is determined by the mode register bits M[2:0].
When a CCIR601 mode is selected (M[2:0] = 4,5), a signal compatible with Chrontel's CH7202 input will be gener-
ated. This entails interpolating the luminance signal by a factor of two, time multiplexing the CrCb signals, delay
matching the CrCb signal to the filtered Y signal, and selecting the 8-bit output mode (register 00h, bit 0).
When a CIF output is selected (M[2:0] = 1), the Cr,Cb resolution will be decimated by a factor of two in both hori-
zontal and vertical directions. This entails band-limiting the CrCb data, decimating in the horizontal direction, stor-
ing one line of decimated CrCb data and averaging the delayed line with the current line. This will position the
chrominance samples according to H.261 standards, and is register controlled (CVL, CHL). When CIF2 is selected,
the chrominance data is decimated in the horizontal direction only.
When QCIF output is selected (M[2:0] = 3), the Y resolution will be decimated by a factor of two in both horizontal
and vertical directions and the CrCb data will be decimated by a factor of four in both the horizontal and vertical
directions. This requires bandlimiting the Y and CrCb data, decimating in the horizontal direction. The Y data is
not be decimated in the vertical direction (since two lines have already been averaged in the matrix multiplier sec-
tion) but the CrCb data will generated a four line average in the vertical direction. When CIF2 is selected, the
chrominance data is decimated by four in the horizontal direction, and by two in the vertical direction.
Format the data stream for the desired type of output:
In addition to the selection of CCIR601 or the different CIF and QCIF modes, the output format can be selected
between 16-bit data (8-bit Y and 8-bit time multiplexed CrCb), and 8-bit data (time multiplexed Cb,Y,Cr,Y data at
twice the rate).
201-0000-032 Rev 3.0, 6/2/99
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