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Buffers are allocated in video memory. Once you create SapView objects using these buffers and call
their Show method one time, the display adapter overlay hardware will keep updating the display with
the buffer contents with no additional calls The pixel format of overlay buffers must be supported by
the display hardware. Typically, overlay buffers support more pixel formats (like YUV) than offscreen
buffers. Also, color keying is supported for overlays. SapView Class determines the behavior of the
overlay regarding key colors.
Dummy Buffers (SapBuffer::TypeDummy)
Dummy buffers do not have any data memory. They may be used as placeholders by transfer resources
when there is no physical data transfer.
Physical Memory Buffers (SapBuffer::TypeUnmapped)
Buffers are allocated as a series of non-contiguous chunks of physical memory. You may not access
their data until they have been mapped to virtual memory addresses using the SapBuffer::GetAddress
method. This type of buffer is useful if the total amount of needed buffer data exceeds the amount of
available virtual memory addresses (2 GB under Windows). To avoid a shortage of virtual memory
addresses, use the SapBuffer::ReleaseAddress method as soon as you are done accessing their data.
Note that you cannot acquire images into these buffers.
Physical Scatter-Gather Memory Buffers (SapBuffer::TypeScatterGatherUnmapped)
These buffers are similar to TypePhysical, except that you can acquire images into them.
Sapera LT User's Manual
Working with Buffers • 63