Wow - thanks for that! It seems to be working well for me in Ubuntu 14.04; I installed G’MIC from the Ubuntu repository and then followed your instructions. Here’s my test result:
After a bit of experimenting, I decided to go with 7 intra-frames into 60fps video for my eight-second exposures. It’s not perfectly smooth of course (I suppose I should try to reduce the exposure length in future), but I’m pretty pleased overall. I’ll probably tweak the tones and darken the night sky slightly before adding some Sigur Rós music.
The frame_step parameter can be used to ‘skip’ some frames for the computation, like considering only one image out of 3 in the image sequence. It is not that useful if the image sequence is a list of image files, but can be if your input image sequence is given as a video file (using command -fade_video).
I’m happy to see this is working as expected! Your resulting video is truely amazing
http://slowmovideo.granjow.net/ might be worth trying too. It’s calculating optical flow and then morphing the images. With that said, you video does look very good already!
Actually, command -morph already does that, but it’s a bit memory consuming right now (because it keeps all interpolated frames in memory). So, I’m working on a ‘streamed’ version of -morph.
Thanks for the feedback. I’ll let you know when I’ve got a proper edit done which I think will contain some other sequences, too.
I see - thanks.
That’s the one I initially tried, but I found that sometimes some stars would be moved along with the lights and then snap back into place on the next “keyframe”. I’d definitely be up for testing a streamed version of G’MIC’s morph!
OK, so I’ve added another set of commands -morph_files and -morph_video which basically works like fade_files and fade_videos, with some extra parameters for the morphing algorithm.
The morphing is done between two consecutive frames by estimating both the forward and backward motion vectors (using an optical-flow like method), then interpolate the frames temporally using these two motion vector fields.
No need to say this can be very time consuming ! (even if like me you have 24 cores!)
How to use it?
First, update your filters, and check the commands are recognized:
gmic -update
gmic -h morph_files
...(help should display here)...
An example of use, using image files as the input (here again, using bash on Linux, may be slightly different on Windows):
(you may want to replace output.png by output.avi to gets an .avi video file as the output).
And that’s almost the same if you have an input video file, instead of a sequence of images:
The smoothness parameter is important to set correctly for the morphing algorithm. Basically if the frames you want to interpolate can be well registered by a rigid motion (translation,shift,…) then the smoothness can be high (like 1 or 1.5). For non-rigid motions, try a lower value (0.1 is medium, 0.01 is low).
After using the update command, the morph_files command doesn’t seem to be recognised.
$ gmic -update
[gmic]-0./ Start G'MIC interpreter.
[gmic]-0./ Update commands from the latest definition file on the G'MIC server.
[gmic]-0./ End G'MIC interpreter.
$ gmic -h morph_files
gmic: GREYC's Magic for Image Computing.
Version 1.7.3, Copyright (c) 2008-2016, David Tschumperle.
(http://gmic.eu)
[gmic] Command 'morph_files' has no description. Try 'gmic -h' for global help.
hum. Isn’t it because of some caching problems ?
Try to get the update file directly from http://gmic.eu/update174.gmic, and put it in your $HOME/.config/gmic/ folder (replacing the older one).
Ah yes, sorry but if you have version 1.7.3 of G’MIC, you need to rename this file $HOME/.config/gmic/cli_update173.gmic. It should work then (but in this case, don’t invoke $ gmic -update, otherwise the cli_update file173.gmic will be overwritten.
[gmic]-0./ *** Warning *** File ‘/home/davido/.config/gmic/cli_update173.gmic’ is not a valid G’MIC command file.
I think you should try $ gmic -update again, this is the ‘good’ way to update. Then, check if the file $HOME/.config/gmic/cli_update173.gmic is a plain text file, and contains the string morph_stream.
If it doesn’t then it means you didn’t get the latest updates, for some strange reasons (maybe web caching…).
@David_Tschumperle found a pretty cool use for this. It works quite well for interpolating in between the frames of precipitation radar sequences. Not yet sure if I can move this into production but I’ll let you know if I can.
I don’t notice much difference in smoothness between the two in this case; I suspect greater movement between each exposure and/or a slower playback speed would show more of a difference. I’ll experiment with this further.
By adjusting the smoothing value I got much, much less unwanted star movement than when using slowmoVideo. (I was using the CPU option with slowmoVideo, not the GPU option which doesn’t seem to be available in my current system setup.)
There is one point in the morph version, shortly after 1:10, where the middle of the horizon twitches; I think this was triggered by inconsistent colours of three dodgy exposures where someone (possibly me) was shining a torch where they shouldn’t have been. For series such as this where crossfading is sufficient I’ll probably stick with the crossfading to avoid unwanted movement, but will try morphing when the combination of exposure time and playback speed result in substantial movement between “keyframes”.
With my 796 source images, using the morph option with 7 intra-frames resulted in more images (6,361) than using the crossfade option with 7 intra-frames (5,565). I’ll do some experimenting with this on a smaller number of images to see if this is consistently the case.