Sequencer: "Capture <Frame Count> live view frames" step sometimes captures incorrect number of frames

[cydonia]

Hi Robin,

I've been building a sequence to semi-automate the taking of flat and dark flat frames and have discovered something strange. Despite the step "Capture <Frame Count> live view frames" being set to 40 frames SharpCap will randomly only capture 39. No dropped frames are reported, it's like it only counts to 39 and then stops. If I change the number to 41 it will do the same and sometimes capture only 40. I've checked the files and it's genuinely capturing 1 frame less rather than just mis-reporting the number.

Exposures are set to 240ms but I have been able to reproduce the issue with the exposures set to 1s too.

I've attached the sequence I create so that hopefully you can reproduce the issue. I have tested with my ZWO ASI183MC Pro camera and the built in "Deep Sky" test camera and get the same behaviour. It seems completely random and so I'm not sure if it's a timing thing or something else.

I can tell it to take single frames however it takes much longer so I would prefer to use live view frames. 39 or 40 frames doesn't make a whole lot of difference for this task but I just thought I would let you know I've seen this strange mis-counting issue.

Thanks.

[admin]

Hi,

thanks for reporting this one - I have just tried to repro the issue based on your sequence and oddly I'm not able to get the same issue to happen. I don't have the ASI183, but used an ASI1600MM instead which has a similar resolution. I was getting 40 frames every time I tested...

The first thing I would say is to check that you have the latest version of SharpCap, as it's just possible that an older version has this bug and the current one doesn't (I doubt that though, but you never know). The next thing that comes to mind is possibly the speed of writing the frames to disk - I was running on my development computer with a fast CPU and fast SSD. Maybe on a slower computer there might be some sort of timing issue with the last frame not being saved because the software has already switched into 'got enough frames' status before it is written. Perhaps worth testing with a small ROI (which would give small, quick to write images) to see if the problem goes away - at least that would give us some information.

cheers,

Robin

[cydonia]

Hi,

Thanks. I'll keep trying to figure out what it is and see if I can figure out a consistent way to reproduce it. Intermittent issues are always a pain.

Admittedly I get 40 frames most times then suddenly only 39. I was running the test sequence with the "Deep Sky" test camera and replicated it with both that and the ASI183MC Pro so it's strange and on different machines too. I think I am on at least a recent version of SharpCap but will check the version.

The machine I use with the ASI183MC Pro has an NVMe drive and so I don't think it was the speed of writing. I'll see if I can figure anything out. One thing I do think happened was that the counter in the bottom right seemed to stop at 39 and not 40 too but I could be imagining it or just didn't see it go to 40.

Anyway I'll keep testing and see if I can help figure out what causes it here.

[admin]

Hi,

OK, do let me know if you catch it reliably. I just tried the deep sky test camera approach, but again I got 41 files in each capture folder (40 images, one capture settings). I didn't spot the counter reading 40/40, but that's probably because it will be hidden immediately that 40 captures are complete and there may not be time for it to even get updated on screen, let alone noticed by the human eye...

cheers,

Robin