ADC-SDI
Rev.
6
To search for input ADC-SDI has 4 channel search modes:
−
Automatic ADC-SDI searches for any possible input signal type. When a signal is
detected, it tries to lock to it, and stops searching.
−
CVBS Ch. 1 ADC-SDI searches for CVBS input on channel 1, and ignores other
input types. When a signal is detected, it tries to lock to it, and stops searching.
−
CVBS Ch. 2 ADC-SDI searches for CVBS input on channel 2, and ignores other
input types. When a signal is detected, it tries to lock to it, and stops searching.
−
S-Video ADC-SDI searches for S-Video input, Luma on channel 1, chroma on
channel 2, and ignores other input types. When a signal is detected, it tries to lock to
it, and stops searching.
If the input type is changed while the card is running, or the signal is missing or lost, the card
will start searching for the type of signal defined by the channel search mode. Channel
search mode settings are described in sections 6 and 7.3.
3.5 Luma / chroma separation filters
The ADC-SDI module has 4 different luma / chroma separation filters to select between.
3.5.1 Comb filter - adaptive between 3-line (½, 0, ½) and no comb filter
This filter will adaptively select between 3-line (½, 0, ½) comb filter and no comb filter.
Adaptive comb filter is available for both luminance and chrominance. The adaptive comb
filter algorithm computes the vertical and horizontal contours of colour based on a block of
3x3 pixels. If there is a sharp colour transition, comb filtering is applied to the two lines that
have fewer colour changes. If there is no colour transition, 3-line comb filtering is used with
filter coefficients (½, 0, ½).
The comb filter can be selectively bypassed in luma or chroma path. If the comb filter is
bypassed in the luma path, then chroma trap filters are used which has a characteristic
according to CCIR601.
The adaptive comb filter algorithm reduces artefacts such as hanging dots at colour
boundary and detects and properly handles false colour in high frequency luminance images
such as a multi burst pattern or circle pattern.
3.5.2 Comb filter - adaptive between 3-line (¼, ½, ¼) and no comb filter
This filter will adaptively select between 3-line (¼, ½, ¼) comb filter and no comb filter, same
functionality as the above, but with different filter coefficients.
3.5.3 Fixed 2-line comb filter
This is a fixed 2-line comb filter with no adaptive selection.
3.5.4 No comb filter
This filter has no comb filter enabled. The luma signal will be filtered with a chroma trap, and
the chroma signal will be filtered with a low pass filter.
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