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New MP-Related Image Compression Manager APIs

The following new multiprocessor-related APIs, which are part of the Image Compression Manager, have been introduced:

• The functions ICMSequenceSetInfo and ICMSequenceGetInfo.

• The constants kICMSequenceTaskWeight and kICMSequenceTaskName.

• The taskWeight and taskName fields of CodecCompressParams and CodecDecompressParams.

The functions ICMSequenceSetInfo and ICMSequenceGetInfo are general property-setters for compression and decompression sequences. They provide support for two properties, kICMSequenceTaskWeight and kICMSequenceTaskName, which allow ICM clients to request that multiprocessor tasks assisting compression and decompression operations use specific task weights and task names.

The task name has no performance impact, but it can be helpful while debugging.

If your compressor or decompressor component creates MP tasks and the taskWeight and/or taskName fields of the CodecCompressParams or CodecDecompressParams structures are nonzero, you should assign the MP tasks weights and/or names using the MPSetTaskWeight and/or MPSetTaskType routines.

The compressedDataSize field has also been added to the CodecCompressParams field. This provides a safer way for asynchronous compressors to return the size of the compressed frame data. (Previously, compressors had to return the size in a field of the image description, which can be an unlocked handle.)

Note that Apple’s multiprocessing APIs provide support for both co-operatively scheduled tasks and preemptively scheduled tasks. The APIs for preemptively tasks allow applications to create symmetrically scheduled preemptive tasks that can be run on a single processor machine, and will take full advantage of multiple processors when they are installed.

For more information, refer to http://developer.apple.com/macos/multiprocessing.html

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