Eliminating bad frames during stacking?

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Bruce G
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Eliminating bad frames during stacking?

Post by Bruce G »

What do you recommend to eliminate short segments of bad frames before stacking? Suppose, for example, that a flag managed to flutter in front of your telescope a couple of times during an acquisition. In my case, a person walked in front of my telescope almost in the middle of a 5000 frame acquisition. AutoStakkert was not amused:*

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While the interruption resulted in only a single interval of bad frames this time, I also wondered about the best way to handle a more serious case, perhaps a few data dropouts in an otherwise good file. What do you recommend to eliminate bad frames, possibly multiple sets of bad frames, to create a contiguous set of good frames suitable for stacking?

Thanks

Bruce G


* The question that immediately pops to mind is "Why didn't AutoStakkert just ignore those frames, since you're only going to process the best ones?" The answer is that the error occurs during the analysis/image alignment portion of the process, where the frame quality has yet to be determined. As a technical application programmer myself, I can definitely see problems in determining relative image quality without making multiple passes, which would add significant and unnecessary time for the bulk of cases. For example, on what basis and at what point should a frame be marked as bad? AS has better things to do. In general, if you want to get good results out of a program, feed it the kind of data that it is expecting, not simply whatever you happened to collect. In other words, although I might want AS to automatically detect and eliminate bad frames, that's not really its job and it is my responsibility to feed it a good data set.


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Re: Eliminating bad frames during stacking?

Post by PDB »

Hi Bruce,

did you try the "Global" parameter in Quality estimation. Might be wrong but thought that could help in siturations like that. (Or passing clouds)

Regards,

Paul


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Re: Eliminating bad frames during stacking?

Post by krakatoa1883 »

I have this problem in late winter and late summer when birds migrate from/to North Africa, while imaging the Sun it can happen that one or more birds are captured in the video. Autostakkert ignores small bird shadows in many instances but sometimes I found them in the stacked image.

I usually check my videos cutting all frames containing birds before feeding AS3!.
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Re: Eliminating bad frames during stacking?

Post by DJD »

You could use SER player to save the good bits to separate SER files using the "set marker" facility then concatenate the good bits to a single SER file
using PIPP ?
If there was a flag in SER player that cut the marked frames it would shorten the process ( perhaps there is a way to "invert" the marker selection ? )
Alternative, I suppose is to save as an AVI and use VirtualDub to edit it.
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Re: Eliminating bad frames during stacking?

Post by Montana »

Ooh that it is annoying. I get this with clouds and it is very frustrating. In Autostakkert you can state which frames you want to ignore. Next to the 1.Open button is a 'limit frames' option. However I have only used this to clip a bad end off the file, I am not sure it is possible to do a middle section.
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Re: Eliminating bad frames during stacking?

Post by LTHB »

If you want to exclude a couple of bad frames from stacking in Autostakkert you can also do that by deselecting them in Autostakkert: Just click through the video (loaded in Autostakkert) frame by frame (or/and use the slider to move through the video) and hit the space-bar for each bad frame. You see the frame details box (upper left side in Autostakkert's image box) go red for the deselected frames.

For excluding just a few frames that should be easier and quicker than cutting the video (e.g. in VirtualDub).

Regards,

Frank


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Re: Eliminating bad frames during stacking?

Post by krakatoa1883 »

I always review my videos with VDub, I cut every bad frame then save what remains and give it to AS3.


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Re: Eliminating bad frames during stacking?

Post by Bruce G »

Paul - I tried a pass with the Global option and AS tolerated the bad frames, but the alignment problem persisted.

Raf's examples with the birds provides another case where trying to describe to a piece of software just what constitutes a bad frame can be very problematic. It's often better to fall back to human intervention for such cases, rather than trying to figure out how to make the software do it.

Raf - Does VDub handle SER, or do I have to use AVI?

David - I know that I can export a frame range from AS. It looks as though PIPP can do the splicing. That may be a way to go.

Alexandra - Unfortunately, the Limit Frames option only allows selecting a single sequence of frames within a file and does not permit splicing

Frank - Bingo! That's the sort of thing I was looking for. I marked the bad frames as you said and the stack worked. The only problem is that when I clicked through the frames, they went two at a time, so I had to mark all the even-numbered bad frames, then go back and mark all the odd-numbered bad frames. Is there any trick that lets you step through the images one at a time?

Thanks all for your suggestions

Bruce G


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Re: Eliminating bad frames during stacking?

Post by PDB »

The only problem is that when I clicked through the frames, they went two at a time, so I had to mark all the even-numbered bad frames, then go back and mark all the odd-numbered bad frames. Is there any trick that lets you step through the images one at a time?
Bruce,

if you click on the frame slider and from there use the arrow keys on the keyboard, this will step frame by frame

Paul


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Re: Eliminating bad frames during stacking?

Post by Bruce G »

PDB wrote: Mon Aug 27, 2018 6:19 am if you click on the frame slider and from there use the arrow keys on the keyboard, this will step frame by frame
Indeed it does!
Thanks Paul!

Bruce G


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