Releases the set of files that were previously requested to be pinned into cache via AK::SoundEngine::PinEventInStreamCache(). The file may still remain in stream cache after AK::SoundEngine::UnpinEventInStreamCache() is called, until the memory is reused by the streaming memory manager in accordance with to its cache management algorithm.
戻り値
AK_Success if command was queued
AK_IDNotFound if the Event ID is unknown (not loaded or typo in the ID)