PRODUCT SPECIFICATION
TMC22091/TMC22191
2-LAYER COMPOSITE
KEY
3-LAYER COMPOSITE
HI KIDS !
HI KIDS !
FOREGROUND
HI KIDS !
27037A
Figure 20. Adding a 3rd Layer
A DOWNSTREAM KEY image comprises the white alpha
characters "HAPPY FACE", and black alpha characters
"Time". This is to be superimposed over the previous 3-layer
composite image. The key signal needed for superimposing
DOWNSTREAM KEY image over the other composite
images is shown to the right. This represents a single bit sig-
nal mapped over the image. When the signal is black (logic
LOW), the DOWNSTREAM KEY image is active, when it
is white (logic HIGH), the previous composite image is
active.
In this illustration, all four source images are static (not mov-
ing). The images input to the TMC22191 can just as well be
"live" (from video camera or VCR sources) as long as:
• Data from those sources is in an input format that the
TMC22191 can accept, and
• The sources either synchronize the TMC22191
(Genlock mode) or are synchronized by the TMC22191
(Master or Slave mode).
Key signals may be generated external to the TMC22191
(Hardware Keying) and use the KEY input pin for control.
Key signals may also be generated within the TMC22191
(Data Keying) by the comparison of input color data with
color data stored in the TMC22191.
The final 4-layer composite image, DOWNSTREAM KEY
over FOREGROUND over MIDGROUND over BACK-
GROUND, is shown in Figure 21.
3-LAYER COMPOSITE
HI KIDS !
KEY
4-LAYER COMPOSITE
HI KIDS !
DOWNSTREAM KEY
HAPPY
FACE
TIME
HAPPY
FACE
TIME
HAPPY
FACE
TIME
27038A
Figure 21. Adding a 4th Layer
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CADEKA [ CADEKA MICROCIRCUITS LLC. ]
