4.13 Multimedia (Graphics and Video) Support
Alpha provides the following instructions that enhance support for graphics and video algorithms:
Mnemonic | Operation |
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MINUB8 | Vector Unsigned Byte Minimum |
MINSB8 | Vector Signed Byte Minimum |
MINUW4 | Vector Unsigned Word Minimum |
MINSW4 | Vector Signed Word Minimum |
MAXUB8 | Vector Unsigned Byte Maximum |
MAXSB8 | Vector Signed Byte Maximum |
MAXUW4 | Vector Unsigned Word Maximum |
MAXSW4 | Vector Signed Word Maximum |
PERR | Pixel Error |
PKLB | Pack Longwords to Bytes |
PKWB | Pack Words to Bytes |
UNPKBL | Unpack Bytes to Longwords |
UNPKBW | Unpack Bytes to Words |
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The MIN and MAX instructions allow the clamping of pixel values to maximium values that are allowed in different standards and stages of the CODECs.
The PERR instruction accelerates the macroblock search in motion estimation.
The pack and unpack (PKxB and UNPKBx) instructions accelerate the blocking of interleaved YUV coordinates for processing by the CODEC.
Implementation Note:
Alpha processors for which the AMASK instruction returns bit 8 set implement these instructions. Those processors for which AMASK does not return bit 8 set can take an Illegal Instruction trap, and software can emulate their function, if required.
Instruction Descriptions