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Cyton-CXP4 frame grabber compatible with Phantom S990 camera

BitFlow, a world leader in frame grabber technology, announced that its Cyton-CXP4 CoaXPress frame grabber has been verified to be compatible with the Vision Research Phantom S990 camera. Recognized as the world's highest-throughput machine vision camera, the Phantom S990 delivers direct data transfer speeds of 9 Gpx/sec (70 Gbps), streaming a maximum of 937 frames-per-second (fps) at 4096 x 2304 (8 bit), or up to 680,000 fps at lower resolution settings.

According to Vision Research, the Phantom S990 applies an advanced, innovative process it dubs "stitching" that divides transmitted images by rows, interleaves the images as they arrive in the frame grabber, and then applies a simple algorithm to "stitch" them back together. While stitching helps the camera realize unprecedented speeds, it also saps the host PC of considerable computing resources, often slowing down processing times. Another issue with the Phantom S990 and similar high-throughput cameras is "thrashing," which occurs when the volume of incoming frames outpaces the CPU of the host PC. Thrashing typically happens at extremely high frames rates, usually 20,000 fps or more.

The problems of both stitching and thrashing underscore the importance of a high-performance frame grabber, or more specifically, several frame grabbers. Because data rates exceed the capacities of a single CXP frame grabber, the Phantom S990 is equipped with 16 outputs and requires four CXP frame grabbers to perform at its full throughput potential. Phantom S990 cameras can run with one or two frame grabbers, yet a proportional reduction in maximum frame rate will be experienced by the system.

Vision Research, the manufacturer of the Phantom S990, recently performed a series of tests on BitFlow CXP frame grabbers validating their compatibility. During testing Vision Research used Cyton CXP4 four-lane frame grabbers configured to achieve a total of 16 CXP-6 single-links. During testing it was uncovered that one of the keys to the success of Cyton CXP4 was its direct memory access engine (DMA). The DMA proved powerful enough to perform re-interleaving of lines on the fly without any CPU usage, an advantage when the Phantom S990 is running in two- or four-bank mode and outputting interleave "chunks" of lines simultaneously to each connected frame grabber.

In the first test, a single Cyton CXP4 was installed in a host PC's PCIe slot connected by four cables to the camera. While not ideal for optimal performance of the Phantom S990, since it only allows for one fourth of the maximum fps, the Cyton CXP4's Single Frame Grabber Mode provided a capable platform for fast configuration and camera focusing via live video provided by running BitFlow Preview software.

Next, four Cyton CXP4 frame grabbers were installed in the PCIe slots. However, each frame grabber was viewed by the operating system as four Virtual Frame Grabbers (VFG). Despite the apparent complexity of operating 16 VFGs, only the first VFG on each physical frame grabber is actually controlled by the end-user. The order of the frame grabbers were then determined — a process that simplifies cable connections — and the overall system was configured and tested in Four Frame Grabber Mode by running BitFlow Preview four times. System testing was performed using BitFlow2x, an application designed to acquire images from one or four frame grabbers simultaneously. BitFlow2x re-interleaves image lines so they appear in memory exactly as they do on the Phantom S990's image sensor. After the images were recorded to host memory, end-users were able to play them back using VCR-style controls or menu commands, as well as save image sequences to a disk for off-line processing. BitFlow's Ximilon application lets end-users modify frame rates on the camera, along with other settings.

To address thrashing, BitFlow provides two methods so the computer is not overwhelmed by a high interrupt rate. The first is "interrupt decimation," a method that fires one system interrupt every N frames with "N" representing a user-configurable number. Once N is set, the driver is aware that each interrupt corresponds to N frames and will transmit this data up to the user. The second method is to simply turn the system interrupt off and poll the board at a high rate. Because BitFlow boards do not require CPU usage for the DMA of the image, this second method works regardless of the Phantom S990's frame rate. Polling simply adds a minuscule amount to CPU usage, less than what is needed to handle a high interrupt rate. This has been tested up to 250,000 fps successfully. Either of the two methods can be enabled with the BifFlow GUI apps or with parameters sent to the API.

Moving forward, BitFlow plans on introducing a CoaXPress-over-Fiber frame grabber for use with high-speed streaming cameras like the new Phantom S991 that features only two QSFP+ modules for fiber cables. An add-on to the CXP 2.0 standard, CoaXPress-over-Fiber paves the way to running an unmodified CXP protocol over a standard Ethernet connection (4 x 10 Gbps) with a single Quad fiber or four SFP+ fibers, resulting either way in a total of 40 Gbps per fiber.


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