Fast exposure / fps capture over gigabit possible?

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markm75
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Fast exposure / fps capture over gigabit possible?

Post by markm75 » Mon Jan 13, 2020 8:56 pm

Anyone have any experience on using sharpcap to capture usb 3.0 over gigabit with higher exposure planetary targets (IE: the bright moon for instance)?

Its my experience it really cant be done, as many frames get dropped over the course of say 500 or more frames even.

Curious if there might be a trick or way of buffering this to be possible however

Thanks in advance

BlackWikkett
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Re: Fast exposure / fps capture over gigabit possible?

Post by BlackWikkett » Tue Jan 14, 2020 1:58 am

It's possible to use gigabit Ethernet with with a USB to Ethernet adapter but gigabit Ethernet has no where near the data transmission capacity to accomplish high speed imaging. Gigabit Ethernet maximum through put using TCP/IP without jumbo frames is about 120 MB/sec. The USB 3 through put is 640 MB/sec. Now most camera's will never push 640 MB/sec but you can easily reach close 200 MB/sec if you lower ROI on a typical camera. You could always limit the frame rate not to go past Ethernet's capacity but this is not reliable. USB is a finicky beast even if you stay within the lanes it was designed to operate in it. Just have a search of SC forums for USB issues. You'll get much better performance and reliable connection using a computer at the scope and remote to this computer if you want to have long range access and control.

-Chris

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admin
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Re: Fast exposure / fps capture over gigabit possible?

Post by admin » Tue Jan 14, 2020 6:58 pm

Hi,

As Chris says, you are much better off keeping the computer close to the USB3 device and then remote controlling the computer. I have seen cameras running at around 300 to 350 MB per second of video data (ZWO174MC, QHY5III-178 for instance), which is way more than the bandwidth of gigabit ethernet. In fact for some cameras and add in USB3 card can be a problem because these add-in cards typically only use a single PCIe lane and the camera bandwidth can exceed the bandwidth of the PCIe lane.

Cheers, Robin

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turfpit
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Re: Fast exposure / fps capture over gigabit possible?

Post by turfpit » Tue Jan 14, 2020 7:56 pm

If you are trying to extend USB and get it to work then have a look at:
https://www.startech.com/uk/Cables/USB- ... B3AAEXT10M
Cost is £135 for a cable and 2 can be daisy-chained to give 20m extension. The extender needs mains power, provided via the supplied AC adapter.

As suggested above (twice), the conventional way is to have a capture PC/laptop at the scope/camera and use a remote connection via another PC/laptop to manage the capture program. Software commonly used to achieve this would be Remote Desktop (Professional version of Windows) together with Remote Desktop Connection (look up RDP Server & RDP Client), TeamViewer or VNC.

VNC Server/Viewer software here https://www.realvnc.com/en/connect/download/vnc/.

Dave

markm75
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Re: Fast exposure / fps capture over gigabit possible?

Post by markm75 » Tue Jan 14, 2020 8:41 pm

Thanks all for the replies.

No i was hoping there was a hack to make this work if even via buffer, but honestly, i'm probably just as well off doing everything on the local mini pc (ssd D drive) in the nexdome at least for highspeed planetary.

I have 3 gigabit runs going to the dome, one goes to the mini pc. As of now all DSO and even some "slower" planetary was working fine over gigabit.

For nina and dso there is no issue, i can continue to send everything to my server location as before. But i guess for sharpcap ill just point that to the local d drive and run a push to the network as needed.

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