Intel 815 manual Gfxblock, Rendering Block 1Eh, Block Type, Block Pattern Format

Intel® 815 Chipset: Graphics Controller PRM, Rev 1.0

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13.3.GFXBLOCK

The GFXBLOCK instruction is used with Motion Compensation. It is a variable length instruction, which contains intra-coded/correction data at the end of the instruction. The DWORD_LENGTH must correspond to the Block Pattern Bits that identify which quadrants of the block have associated correction data. When the horizontal or vertical block pattern are disabled the block pattern bits are assumed to be set. All of the block pattern bits must also be set when the Prediction Type is “intra- coded”. Having no correction data is also valid to enable support for skipped blocks.

When the Block Pattern Format is disabled, bits [29:28]=0 and any Y, Cr, or Cb pattern bits, bits [27:22], are set, the error data must be set to 0. The alternative is to ensure that the Y, Cr, or Cb pattern bits, bits [27:22], are set to 0.

DWord	Bits		Description
0	31:29	Client : 03h – Rendering Engine
	28:24	Rendering Block : 1Eh
	23:16	Opcode: 00h
	15:0	DWORD_LENGTH : 5 + Intra-coded/Correction Data DWords
1	31:30	Block Type:
		00	= Reserved (Macroblock – The Luminance and Chromanance blocks are all
			predicted from this instruction. The Height, Width and Motion Vectors are
			shifted right 1-bit when processing the chromanance blocks.)
		01	= Luminance (Y) Block
		10	= Chromanance Red (Cr) Block
		11	= Chromanance Blue (Cb) Block
	29:28	Block Pattern Format:
		00	= Disable Block Pattern Usage and Intra-coded/Correction data. The Height and
			Width are not constrained and need only be less than 1024. Intra-
			coded/Correction data is not allowed in this state.
		01	= Single Block - Uses bit 27 for a Luminance block and bits 23,22 for the
			chromanance blocks respectively. If intra-coded/ correction data is present the
			order of the data is row-major for the entire width of the block.
		10	= Halves: Left and Right - Uses bits 27, 26 for the two halves of the Luminance
			block respective. Intra-coded/ correction data is delivered in row-major order
			for the left half of the block, followed by the data for the right half of the block.
			Chromanance blocks are always considered to be Single blocks, using bits 23
			and 22 for the Cr and Cb blocks, respectively.
		11	= Quadrants: Upper-left, Upper-right, Lower-left, Lower-right - Uses bits 27:24 for
			the four quadrants of the Luminance block respective. Intra-coded/correction
			data is delivered in row-major order for the four quadrants of the block
			beginning with the upper-left quadrant and proceeding to the upper-right, lower-
			left and lower-right quadrants. Chromanance blocks are always considered to
			be Single blocks, using bits 23 and 22 for the Cr and Cb blocks respectively.
	27:24	Y Block Pattern: Enable/disable correction data for the Y block(s)
1	23	Cr Block Pattern: Enable/disable intra-coded/correction data for the Cr block

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