Miranda NV5100MC Master Control, Reference Manual

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66 Rev 2.10 • 17 Feb 11
4. MCPMs
MCPM Architecture
• Video gain.
These parameters apply only to video keyers:
• Self-key enable.
• S-Shape enable.
• Luma filter bypass.
• Chroma filter bypass.
• Additive key mix.
Video Clip and Video Gain
Key clip and key gain are parameters of a transform applied to the incoming key signal. The con-
figurer may set the key clip parameter from 0 to 100%. The configurer may set the key gain param-
eter from 0 to 1023, where 1 is unity gain.
S
Warning: the term “clip” is misleading. “Offset” is more accurate.
S
Video gain in MCEs is different: for MCEs, the gain range is 0 to 63.9375 in fractional steps of
1/16. For other MCPMs, the range is 0 to 1023, in integral steps.
Before it applies clip and gain, the MCPM or MCE normalizes the key luminance to the range [–0.5
to +0.5]. The “clip” value given during configuration is a
percentage :
Offset = –0.5 + percentage × 1.0
Thus, the clip and gain transform is:
K
O U T
= (K
IN
– offset) × gain
Because the gain ranges from 0 to 1023, K
O U T
can be very large. The normalization process clips
K
O U T
to the range [–0.5 to +0.5].
The following graphs illustrate some of the effects of offset, gain, and clipping.
Luminance (the key) is a black-to-white value. When the keyer is mixed with upstream video,
black admits 0% of the keyer’s fill. White admits 100% of a keyer’s fill. Thus, white means that the
fill is opaque; black means that the fill is transparent, and the shades in between represent variations
in keyer opacity.
Gain = 1, Clip = 50% Gain = 4, Clip = 50% Gain = 0, Any Clip Gain = 1023, Clip = 50%
Gain = 2, Clip = 75% Gain = 2, Clip = 100% Gain = 2, Clip = 0% Gain = 2, Clip = 25%
Range Limit
[–0.5 to +0.5]
Range Limit
[–0.5 to +0.5]
Input Range
[–0.5 to +0.5]
Input Range
[–0.5 to +0.5]
Input Range
[–0.5 to +0.5]
Input Range
[–0.5 to +0.5]
A B C D
E F G H