Texas Instruments TMS320C64x DSP manual x Co-Sited Scaling

Video Output Filtering

Figure 4–20. 2x Co-Sited Scaling

a

b

c

d

e

f

g

YCbCr 4:2:2 co–sited

source pixels

a

a’

b

b’

c

c’

d

d’

e

e’

f

f’

g

2⋅ upscaled output

Y’b = Yb Cb’c = Cbc

Cr’c = Crc

– Luma (Y)	– Chroma (Cb/Cr)
sample	samples

Y’d’ = (–1Yc+ 17Yd + 17Ye – 1Yf ) / 32

Cb’d = (–1Cba+ 17Cbc + 17Cbe – 1Cbg ) / 32 Cr’d = (–1Cra+ 17Crc + 17Cre – 1Crg ) / 32

Figure 4–21. 2x Interspersed Scaling

YCbCr 4:2:2
interspersed	a	b	c	d	e	f	g

source pixels

2x upscaled

YCbCr 4:2:2

a a’ b b’ c c’ d d’ e e’ f f’ g h’

co-sited output

Y’a = Ya Y’e’ = (–1Yd+ 17Ye + 17Yf – 1Yg ) / 32

Cb’d = (–3Cbab+ 101Cbcd + 33Cbef – 3Cbgh ) / 128

Cr’d = (–3Crab + 101Crcd + 33Cref – 3Crgh ) / 128Cb’e = (–3Cbab+ 33Cbcd + 101Cbef – 3Cbgh ) / 128 Cr’e = (–3Crab + 33Crcd + 101Cref – 3Crgh ) / 128

–Luma (Y)	–Chroma (Cb/Cr)
sample	samples

4.4.4Edge 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 (2⋅ co-sited) is shown in Figure 4–22.

Figure 4–22. Output Edge Pixel Replication

a a b c n–2 n–1 n n n–1

Horizontal Image Size

a

a’

b b’

c

n–2 n–2’ n–1 n–1’ n

n’

Trailing edge

replicated pixels

Leading edge

replicated pixel

Y’a = Ya

Y’b = Yb

Y’c = Yc

Y’n–2=

Y’n–1=

Y’n = Yn

Yn–2

Yn–1

Y’

’ = ƒ(Y , Y , Y

b’

, Y

c

)

Y’n’

= ƒ(Yn–1, Yn, Yn, Yn–1)

Y’

= ƒ(Y , Y

, Y

, Y )

a

a’ a’

b’

b’

c’

a’

d

Y’n–1’= ƒ(Yn–2, Yn–1, Yn’, Yn)

– Luma (Y)

Chroma (Cb/Cr)

–

Y’

= ƒ(Y

, Y

, Y

, Y

)

sample

samples

n–2’

n–3

n–2

n–1’

n

SPRU629 Video Display Port 4-23