Intel 815 manual 212

Intel® 815 Chipset: Graphics Controller PRM, Rev 1.0

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DWord	Bits		Description
2	31:26	Reserved: 00h
	25:16	Horizontal Origin: An unsigned integer specifying both the upper-left pixel of the
		destination block and the origin of the motion vectors in the reference frame(s). This
		value must be a multiple of the width. The valid range is 0 – 1023.
	15:10	Reserved: 00h
	9:0	Vertical Origin: An unsigned integer specifying both the upper-left pixel of the
		destination block and the origin of the motion vectors in the reference frame(s). This
		value must be a multiple of the height. The valid range is 0 – 1023.
3	31:26	Reserved: 00h
	25:16	Height: An unsigned integer specifying the height of the destination block and the
		source block(s), if required. The valid values for this field are dependant on the
		Block Pattern Format as follows:
		Disabled	Valid range: 1 – 1023 (used for skipped macroblocks)
		Single	Valid values are 2,4,8
		Halves	Valid values are 2,4,8
		Quadrants	Valid values are 4,8,16
	15:10	Reserved: 00h
	9:0	Width: An unsigned integer specifying the width of the destination block and the
		source block(s), if required. The valid values for this field are dependant on the
		Block Pattern Format as follows:
		Disabled	Valid range: 1 – 1023 (used for skipped macroblocks)
		Single	Valid values are 2,4,8
		Halves	Valid values are 4,8,16
		Quadrants	Valid values are 4,8,16
4	31:0	Forward Motion Vector (see the Motion Vector Format below)
5	31:0	Backward Motion Vector (see the Motion Vector Format below)
6 – …	N/A	Block Intra-coded/Correction Data: Each double word (32 bits) contains packed
		8-bit data or 16-bit data depending on the Prediction Type:
		Intra-coded Block	Four 8-bit values packed in 32 bits. The least significant byte
			contains data for the left most pixel, spatially.
		Predicted Block	Two 16-bit values packed in 32 bits. The least significant
			word contains data for the left most pixel, spatially.
	N/A	…

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