Dalsa C1240, User Manual

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210 • Operational Reference Nano Series GigE Vision Camera
Acquisition Buffering
All acquisitions are internally buffered and transferred as fast as possible to the host system. This
internal buffer allows uninterrupted acquisitions no matter of any transfer delays that might occur
(such as acquisition frame rates faster that the Gigabit Ethernet link or the IEEE Pause frame ).
Only when the internal buffer is consumed would an Image Lost Event be generated.
Understanding the feature - TransferQueueMode
When acquisitions and transfers are not coupled together (i.e. TransferControlMode=
UserControlled) the user has control on the size of the acquisition circular buffer and the
management of how acquired frames are handled when the frame transfer is slower.
The feature — TransferQueueMode provides two methods to handle the number of acquired frames
when those frames are greater than the circular buffer count, such as when doing a continuous
grab and frames transferred out is slower than the acquisition frame rate.
FirstInFirstOut:
Acquired frames are stored in the circular buffer addressed by the Buffer Write Index. When the
write index catches up to the read index, acquired frames are discarded until the next buffer is
transferred out and that buffer is free to be over written.
firstInFirstOut_CircularWhenStopped:
This has an automatic dual behavior operating mode. With continuous acquisitions with transfers
slower than the incoming frames, new frames are discarded when the circular buffer is filled, just
as the first mode described previously.
In the case where AcquisitionStart=true and TransferStop=true, no acquired frames are discarded
as they are stored into the circular buffer. New frames overwrite older frames when the circular
buffer is full. This mode effectively allows capturing image frames (dependent on the size of the
circular buffer) that precede the point in time when then frames are read out (TransferStart=true).
Circular Buffer
Write/Read
Direction
Buffer Read Index
Buffer Write Index
Buffer Quantity set by
“transferQueueMemorySize”