PNX1700EH,557 NXP Semiconductors, PNX1700EH,557 Datasheet - Page 365

• Manufacturer Part Number: PNX1700EH,557
• Manufacturer: NXP Semiconductors

Specifications of PNX1700EH,557

• Operating Temperature (min): 0C
• Operating Temperature Classification: Commercial
• Mounting: Surface Mount
• Lead Free Status / RoHS Status: Not Compliant

Philips Semiconductors
Volume 1 of 1
PNX17XX_SER_1
Preliminary data sheet
Chroma keying allows overlaying video depending on whether the pixel lies within a
range of color values. This feature allows video transparency or “green screening”—a
technique for compositing foreground imagery with a background.
Color keying is considered to be a subset of chroma keying and can be achieved by
setting the color range accordingly; because of the similarity between Chroma and
Color keying (the difference being a color range instead of a fixed single color), this
document will use the terms interchangeably, even though QVCP implements both
functionality. The chroma/color key result is used for mixing functions downstream.
For example, color keying can be used to determine which pixels should contain
motion video. The color key function will compare the pixels of a layer with the color
key register and place motion video from another layer in those pixels that match. The
Color Key is generated in each layer (before color space conversion). Each byte lane
of the expanded RGB 8:8:8 or YUV 4:4:4 new pixel is passed through an 8-bit Color
Key AND mask. (For the YUV 4:2:2 input format, the U and V samples are repeated
for every other pixel). The result in each channel is compared to the register values
for Color Key Lower Range and Color Key Upper Range. Every layer can use up to
four color keys. When the pixel component is equal to a range register value or is
within the range, the result of the comparison for that byte lane is true (1). If it’s
outside the range, the result is 0. The results from the three byte lanes are used as
keys in the 8-bit Color Key Combining ROP. This ROP is a mechanism used for
extreme flexibility in keying and is located in the layer. (It is not to be confused with
ROP in the mixer which follows each layer.)
CnKey0_Layer is determined by checking if the B(V) color component is within the
chroma key range.
CnKey1_Layer is determined by checking if the G(U) color component is within the
chroma key range.
CnKey2_Layer is determined by checking if the R(Y) color component is within the
chroma key range.
Cn represents one of the four possible key colors. Since four colors are possible per
layer, four different ROPs exist for determining which component of which key color
should lead to a color key hit. If the color component is within the range, the key is set
to 1. If it’s not, the key is set to 0.
Table 2: Color Key Combining ROPs
ROP Bit
[0]
[1]
[2]
[3]
[4]
[5]
[6]
[7]
Rev. 1 — 17 March 2006
Key2
0
0
0
0
1
1
1
1
Key1
0
0
1
1
0
0
1
1
© Koninklijke Philips Electronics N.V. 2006. All rights reserved.
PNX17xx Series
Chapter 11: QVCP
Key0
0
1
0
1
0
1
0
1
11-8