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USB 3.1 cameras with Fresco driver limited to <6 MB

KB Number: 10291
Last Revision Date: 10/12/2016

This article discusses the limit on image size when using USB 3.1 cameras and the Fresco driver. 

For USB 3.1 users with a Fresco card and driver, the Fresco driver uses a ring buffer to store images coming from the the camera. The buffer is limited to 60 MB by default. FlyCapture uses 10 image buffers to store images per default. This results in a maximum image size of 60 MB/10 = 6 MB.

We recommend using the PGRxhci driver, which does not have this limitation.

Alternative workarounds include one of the following:
1) Use the FC2Config structure in the FlyCapture2 API to reduce the number of FlyCapture image buffers.
2) Use the Fresco card with Windows 8, which uses the Microsoft driver.
3) Use a Renesas or Intel host controller and driver.
4) Increase the Fresco ring buffer size (see below).

To determine image size:
Image size in MB = resolution X pixel format in bytes per pixel / 1000000

Pixel Format   BPP
 8-bit  1
 12-bit  1.5
 16-bit  2
 24-bit  3

For example, a 1280 x 960 RGB image would be 3.7 MB.

Use the Custom Video Mode tab in FlyCap2 to adjust the camera's pixel format and resolution.

To increase the ring buffer size:
1. Disable the Fresco controller.
2. Modify the following registry value:

KEY:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\FLxHCIc\Parameters

DWORD name:
BulkInRingBuffers

Note: If BulkInRingBuffer registry does not exist, create this Dword in the location mentioned above.

3. The default size is 48 pages. Change this to 256 pages. The configured value must be a multiple of 8 to a maximum of 256 pages.
4. Enable the Fresco controller after making the change.

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