Frames Dropped After Reducing Exposure Time

[joshinoregon]

I understand verifiable novels have been written within this forum regarding frames drops and FPS rates, so I have done about as much troubleshooting as I could to narrow down what I believe to be a bug within the latest version of SharpCap (v. 4.1.12371.0)

*ISSUE*

If the exposure time is set to a value greater than ~3 seconds, and then reduced to something below ~3 seconds, all subsequent frames will be dropped. The only way for frames to be recaptured again is to increase exposure time to a value greater than ~3 seconds.

*BEHAVIOR*

When I first connect my camera, all frames are being captured at the appropriate FPS. For example, upon initial connection, my exposure time is set to 50ms, and I am getting 20 FPS, and all frames are being captured in live view. Now I increase my exposure time to around 5 seconds (so I can focus). Upon reaching focus, I would try to use the Smart Histogram before imaging, and SharpCap could not capture any frames. I now know this is because the exposure time was decreasing below ~3 seconds. Further testing showed this behavior would manifest when using the auto settings in the flat capture tool...again, because the exposure was being lowered below ~3 seconds. Finally, I tested this on my own by

1. Connecting my camera at 50ms and ensuring frames are being captured at 20 FPS
2. Raising my exposure time to 5 seconds and ensuring frames are being captured
3. Lowering exposure time back to 100ms...and at this point SharpCap would not capture any frames if the exposure time were set to less than ~3 seconds.

*Camera*

ASI 1600MM Pro

*Troubleshooting*

My first suspicion was that my installation of SharpCap was corrupted. I uninstalled and reinstalled v. 4.1.12371.0 and the issue persisted.

My next suspicion was I was dealing with hardware issues, either on my laptop or USB cables being used. I swapped around USB cables...in each case ensuring...

1. Cables were 3m or less in length
2. Direct connection from my camera to the laptop (no external USB hub). There are no adjacent USB ports on my laptop, leaving me to assume there is no internal USB hub either
3. I tried the USB 3.0 cable that came with my camera, the USB 2.0 cable that came with my camera, and a third party USB 3.0 cable.

The issue persisted

I then noticed I could NOT replicate this issue with my guide camera (ASI 120MM Mini). So then I started playing around with MONO8 vs MONO16, binning, and resolution. No Avail, no matter the combination of camera settings, I could not resolve the issue.

Then I suspected USB issues with my laptop itself? I installed SharpCap v 14.1.12371.0 on my desktop PC. The same USB cables were used, same settings were tried with camera settings, and the issue was replicated. So at this point, I felt I had ruled out any hardware (occurring on 2 different PCs with different cables).

Now I feared that the issue may be with camera itself? I then remembered I had an old retired laptop that had an old version of SharpCap installed. Upon dusting it off, and waiting for it to boot, I confirmed that it was running SharpCap v. 4.0.9268.0. I connected all my equipment...and huzzah! I could NOT replicate the issue. I could set my camera to its highest settings...MONO16, no binning, full resolution and capture frames at 50 ms. I could then raise my exposure to 10 seconds and capture frames. I could then lower my exposure down to 50 ms again and continue capturing frames.

At this point, I was strongly suspecting a bug within the latest version of SharpCap.

I took my new laptop (the laptop where I originally experienced these issues) and uninstalled SharpCap. I then rolled back to v. 4.1.122430 and I can no longer replicate the issue.

At this point I strongly suspect this bug was introduced somewhere between version 4.1.12243.0 and 4.1.12371.0.

I have attached a log of the behavior...starting at a low exposure time, raising it beyond ~3 seconds, and then lowering it again below ~3 seconds for frames to begin being dropped.

[admin]

Hi,

thanks for the comprehensive report - I have just tested this with my (very similar) ASI1600MM-Cool, and I see the same problem too. I've tracked back and can see that the introduction of a new ZWO SDK (ASICamera2.dll) in SharpCap 4.1.12281 seems to be the source of the problem - going back to the old SDK fixes the problem. I think what is happening is that SharpCap puts the camera into still mode for exposures of 2s or above, and things seem to be failing when SharpCap puts the camera back into video mode for shorter exposures.

This seems like something that ZWO will have to fix, so I will pass the report on to them.

For a workaround, you can go back to SharpCap 4.1.12251 or earlier to get a working version of the SDK (you can download old versions from our download page, but you have to uninstall your newer version before you can install the older one - your settings will still be saved).

Another workaround with the latest version seems to be plugging the camera in over a USB2 cable - for me that seems to sidestep the issue, but obviously limits frame rates.

cheers,

Robin

[admin]

Hi,

just to confirm that I have been in contact with ZWO and they are hoping to release an updated SDK that fixes the issue soon. Please use an older version of SharpCap with an older ZWO SDK (ASICamera2.dll 1.34 not 1.35) as a workaround for now.

thanks,

Robin