Hi,
Like the title said, i would like to use 2 cameras (V100:R2) in GrayScaleMode, synchronized with the cModuleSync. My USB Bandwidth is shared between my 2 ports, and i would like to keep the same Frame resolution.
I use the sample "FrameSynchronization.cpp", and it works fine in segmentMode. It doesn't anymore in GrayScaleMode, probably because of the USB bandwidth. To solve this, I have 2 solutions:
-Dropping the framerate from 100 to 50% for each camera. It works, but I don't want this.
-Setting the frame decimation rate to 1/2/4 or 8... It doesn't work. Why? Shouldn't the bandwidth usage be reduced?
So these solutions are no good... If you got any idea on how i can solve this problem or make the option 2 works, i'll take it.
Thanks for your help.
2 Cameras and GrayScaleMode
Re: 2 Cameras and GrayScaleMode
Hi Alexis,
Unfortunately reliable raw grayscale on our cameras is very difficult.
When the cameras are running at the full frame rate, even though the aggregate data rate is well below the maximum throughput of the USB channel, the camera's has no mechanism to throttle the data based on USB congestion. Therefore if the transfer of raw grayscale data from the camera is preempted by the USB channel, the frame will become corrupted and be dropped.
The reason lowering the Frame Rate on the camera resolves the problem is because the rate at which the frame data is clocked out of the camera is stretched in time. Since the data rate is lowered it can survive being preempted by the USB channel without overflowing it's internal buffers.
Frame Decimation only drops frames but during the read-out of any given frame, the data rate is still at the highest rate.
On our more recent cameras, we've changed our approach for Raw Grayscale because the expectation that you can insist on running full frame rate with this amount of data has proven unrealistic. One R2 would generate 30MB/second. This is certainly below the theoretical maximum of USB 2.0 but in practice, it's difficult to achieve this data rate. The Flex13, for example, will guarantee proper delivery of raw grayscale but can't guarantee the rate. Instead it will meter out the data based on USB bandwidth availability. On my PC, the Flex13 achieves 21 frames/second in Raw Grayscale. Of course, it can't be synchronized with other cameras because of this.
D
Unfortunately reliable raw grayscale on our cameras is very difficult.
When the cameras are running at the full frame rate, even though the aggregate data rate is well below the maximum throughput of the USB channel, the camera's has no mechanism to throttle the data based on USB congestion. Therefore if the transfer of raw grayscale data from the camera is preempted by the USB channel, the frame will become corrupted and be dropped.
The reason lowering the Frame Rate on the camera resolves the problem is because the rate at which the frame data is clocked out of the camera is stretched in time. Since the data rate is lowered it can survive being preempted by the USB channel without overflowing it's internal buffers.
Frame Decimation only drops frames but during the read-out of any given frame, the data rate is still at the highest rate.
On our more recent cameras, we've changed our approach for Raw Grayscale because the expectation that you can insist on running full frame rate with this amount of data has proven unrealistic. One R2 would generate 30MB/second. This is certainly below the theoretical maximum of USB 2.0 but in practice, it's difficult to achieve this data rate. The Flex13, for example, will guarantee proper delivery of raw grayscale but can't guarantee the rate. Instead it will meter out the data based on USB bandwidth availability. On my PC, the Flex13 achieves 21 frames/second in Raw Grayscale. Of course, it can't be synchronized with other cameras because of this.
D
Re: 2 Cameras and GrayScaleMode
Hi,
Thanks for your quick answer. I guess i will try to find a workaround with the segment mode and by lowering the frame rate.
Alexis.
Thanks for your quick answer. I guess i will try to find a workaround with the segment mode and by lowering the frame rate.
Alexis.