fastest way to pass an image to the GPU

Hi,

I am using Intel's VME extension to calculate ME and the time that it take to pass the image to the GPU is very long about 1Msec

I have tried 2 methods: 

#1 Map /Unmap - about 0.4 Msec for 1280*720 image

queue.enqueueMapImage(*pRefImage,CL_TRUE,CL_MAP_WRITE_INVALIDATE_REGION,origin, region,  &row_pitch,NULL,NULL,NULL);

memcpy(prefImageMemory,pRefBuf,arraySizeImageBytes); // Memory use HOST memory 

queue.enqueueUnmapMemObject(*pSrcImage,psrcImageMemory,NULL);

#2 enqueueWriteImage  - about 0.7 Msec for 1280*720 image

queue.enqueueWriteImage(srcImage, CL_TRUE, origin, region, currImage->PitchY, 0, currImage->Y);

Why doesn't it take so long?

How can I improve this?

Can I call map once and than unmap after each change in the image memory and save the "map" time/

Regards,

Raz