Texas Instruments TMS320DM648 manual 2x Interspersed Scaling, Output Edge Pixel Replication

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Video Output Filtering

		Figure 4-17.		2x Interspersed Scaling
YCbCr 4:2:2
interspersed a		b	c	d	e	f	g
source pixels
2x upscaled	a	a’ b	b’ c	c’ d	d’ e	e’ f	f’ g h’
YCbCr 4:2:2
co-sited output
Y’a = Ya						Y’e’ = (-1Yd+ 17Ye + 17Yf - 1Yg ) / 32
Cb’d = (-3Cbab+ 101Cbcd + 33Cbef - 3Cbgh ) / 128						Cb’e = (-3Cbab+ 33Cbcd + 101Cbef - 3Cbgh ) / 128
Cr’d = (-3Crab+ 101Crcd + 33Cref - 3Crgh ) / 128
						Cr’e = (-3Crab+ 33Crcd + 101Cref - 3Crgh ) / 128
-Luma (Y)		- Chroma (Cb/Cr)
sample		samples

4.4.4 Edge Pixel Replication

Because four tap filters are used on the output, the first and last two pixels on each line must be mirrored. An example of how the filter uses the mirrored pixels for the luminance filter (2x co-sited) is shown in Figure 4-18.

Figure 4-18. Output Edge Pixel Replication

a a b c n-2 n-1 n n n-1

Horizontal Image Size

Trailing edge

a

a’

b b’

c

n-2 n-2’ n-1

n-1’ n

n’

Leading edge

replicated pixels

replicated pixel

Y’a = Ya

Y’b = Yb

Y’c = Yc

Y’

=

Y’n-1 =

Y’n = Yn

n-2

Yn-2

Y

Y’ ’ = ƒ(Y , Y , Y , Y )

Y’ = ƒ(Y , Y , Y , Y )

n-1

Y’n’ = ƒ(Yn-1, Yn, Yn, Yn-1)

a

a’ a’ b’

c

b’

a’ b’

c’ d

Y’n-1’= ƒ(Yn-2, Yn-1, Yn’, Yn)

Luma (Y)

Chroma (Cb/Cr)

-

-

Y’n-2’= ƒ(Yn-3, Yn-2, Yn-1’, Yn)

sample

samples

Examples of luma edge and chroma edge replication for 2x interspersed to co-sited output are shown in Figure 4-19and Figure 4-20, respectively.

Figure 4-19. Luma Edge Replication

a

a

b

c

x

y

z

z

y

Horizontal Image Size

Trailing edge

a a’

b

b’ c

x x’

y

y’ z z’

Leading edge

replicated luma

replicated luma

Y’a = Ya

Y’b = Yb

Y’c = Yc

Y’x = Yx

Y’y= Yy

Y’z = Yz

Y’z’ = (-1Y

y + 17Yz + 17Yz - 1Yy) /32

Y’b’ = (-1Ya+ 17Yb + 17Yc - 1Yd) /32

Y’y’ = (-1Yx+ 17Yy + 17Yz - 1Yz ) /32

Y’a’ = (-1Ya+ 17Ya + 17Yb - 1Yc) /32

Y’x’ = (-1Yw+ 17Yx + 17Yy - 1Yz ) /32

SPRUEM1 –May 2007 Video Display Port 105

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