AMD SC3200 manual Color Key and Alpha Blending Logic, 324

32581C Video Processor Module

Start

Use selected cur-	Yes	Cursor color
sor color for pixel		key matches
		graphics value
	Yes		No
		Pixel outside
Use graphics
value for this pixel		the video
		window
			No

Blend graphics

values and video values using the alpha value for this window

	Pixel inside		1	No	“Graphics2
					inside Video”
	alpha window
					is enabled
		Yes				No
No	Pixel value3				Pixel value3
	matches				matches
	normal color				normal color
	key				key
		Yes				No

Yes

Yes

Replace the value with the color register value

Yes	Color register		COLOR_CHROMA		COLOR_CHROMA	Yes
	enabled for this
			_SEL = 1		_SEL = 1
	window			Yes
		No	No		No

COLOR_CHROMA

_SEL = 1

Yes

Notes:

	No
Use video value		Use graphics	Use video value	Use graphics
for this pixel		value for this pixel	for this pixel	value for this pixel

1)Alpha window should not be placed outside of the video window.

2)“Graphics inside Video” is enabled via bit GFX_INS_VIDEO in the Video De-interlacing and Alpha Control register (F4BAR0+Memory Offset 4Ch[8]).

3)The “Pixel Value” refers to either the Video value or the Graphics value, depending on the setting of bit COLOR_CHROMA_SEL in the Display Configuration register (F4BAR0+Memory Offset 04h[20]).

Figure 7-12. Color Key and Alpha Blending Logic

324 AMD Geode™ SC3200 Processor Data Book