Pco Edge 3.1, Руководство пользователя

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RING BUFFER AND FIFO A4.4.3
The pco.edge with USB 3.0 interface has a small internal buffer
memory integrated. Each recorded and read out image is directly
transferred to this internal buffer and subsequently the image is
transmitted to the computer, where it is either stored into the RAM or
onto the hard disk drive. There are two transfer modes available: Ring
Buffer and FIFO buffer which can be accessed via SDK function:
PCO_SetStorageMode
(see SDK manual).
If for some reasons the USB 3.0 runs slower than usual the Ring
Buffer mode renders the last image faster than the FIFO Buffer mode.
This may be helpful to focus on an object, for example.
Ring Buffer (in camera memory-standard mode)
As described the read out and recorded image is directly
transferred into the internal buffer memory. Subsequently the
next image is stored to the next free space. For the
transmission from the camera to the computer always the
most recent image is used, which works fine in case the
computer does not do anything else than transfer images to its
internal storage memory (RAM).
Now, if the transmission speed of the computer system is
interrupted by e.g. software, it can happen that images get
lost, because in Ring Buffer mode the most recent image has
to be transmitted to the PC. In case of a delay in transmission,
the image in the memory, which waits for transmission will lose
its status as most recent image to the next image, and will be
disregarded for transmission. Hence this image will be
irretrievably lost. Since in Ring Buffer modus always the
most recent image is transferred, i.e. the best real-time
transfer, it is the ideal modus for, e.g. focusing an object.
FIFO Buffer (in camera memory)
Like above the read out and the recorded image is directly
transferred into the internal buffer memory. Subseqently
the next image is stored to the next free space in memory.
If all the memory space is occupied the camera stops
storing. In FIFO buffer mode as the name suggests, FIFO
= first-in first-out, the first stored image is read-out from
the memory first and subsequently transmitted to the
computer. This as well works fine in case the computer
does not do anything else than transfer of images to its
internal storage memory.
However, if the transmission speed of the computer system is
interrupted by e.g. software, still the first stored image is readout, and
then the next image is read out and transmitted. However there could
be a delay time (but need not). If the slowdown fills the FIFO
completely, the camera stops storing images and the next image will
irretrievably lost as well, but in this mode it is lost before storing. This
mode is ideal for users who need maximum transmission certainty;
an image loss is very unlikely.
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