Testing temporal consistency with the “Black Crayon Graffiti” filter, not too bad:
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I found out I added a special mode to the plugins 5 years ago that I just re-discovered. 
Besides having each filter available as a separate plugin, there is also a “generic G’MIC plugin”, which is just an option to enter the commands as text to be sent to the G’MIC interpreter. That way any command (or sequence of commands) can be entered from one single plugin, very comfortable. I just added 8 normalized float parameters to the plugin and made them available for the interpreter as separate variables, so that you can now even automate the command for each rendered frame.
In the screenshot below, the first parameter of the fx_crayongraffiti2 command (i.e. the amplitude) gets modulated by the first slider in the plugin, which can be controlled by the Natron scripting or automation API.
Same thing in After Effects:
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Would be lovely to have this as an MLT plugin so that Kdenlive, Shotcut, Synfig and others could benefit from it. Not to mention standalone cases like this where millions of videos are generated.
How complex would it be? Would you be interested in developing it? Maybe the community could set up a fundraiser if so?
How long did it take to render this?
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I agree.
I have never used or developed for MLT, Kdenlive, Shotcut, etc., but the G’MIC C bridge library I developed some years ago (and which has since then been part of the regular G’MIC distribution) allows a developer to easily integrate G’MIC in other applications or plugin standards without any dependencies.
Well, I just downloaded Kdenlive and Shotcut and made a quick proof-of-concept filter using the frei0r SDK (which is one of the standards that MLT is based on). Within minutes I had G’MIC running in both Kdenlive and Shotcut as a plugin:
The plugin API seems a bit simple/limited, it does for example not appear to have a text input or button parameters, but in principle it works just like in the other hosts.
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How long did it take to render this?
About 8 minutes I think on my crappy 10 year old notebook
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Wow! Amazing! <3
Can we test this?
PS
I wonder if this is the same approach that Flowblade used. 
I have found a way to enable text input in Kdenlive I think.
I’ll see if I can make a frei0r public test build tomorrow, Windows only for now though!
And this will only include the generic G’MIC plugin (where you can enter any command as a parameter), not the whole package of the gui filters with proper parameter names, since filters for Kdenlive/Shotcut need to be put each into a separate library and also need a separate GUI definition file, so I would first come up with a decent batch compile/build/export solution, just like for After Effects.
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I will still be in the process of cleaning and updating the sources for still a while, removing dependencies and generally making stuff easier to understand (also for myself), while still maintaining compatibility with my commercial plugins and APIs.
As before, I will also make all my sources available (except for proprietary SDKs like Adobe AE, which developers can download themselves without costs) and put them dual-licensed under CeCILL-C and CeCILL v2.0, either in my own public repository on Github or in the G’MIC community repository (or both).
This will include sources to build a G’MIC plugin for Adobe After Effects, Adobe Premiere Pro, OpenFX, frei0r/MLT and possible some other plugin standards. Binaries for Windows (and later possibly MacOS and Linux) will also be provided.
But give me some more time, I hardly have any free time at the moment, but I’m sure we’ll get there
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This is really amazing. Thanks for the great work you’ve done. Do take it easy and no rush. Stay safe! <3
Kdenlive is rather fragile and has a lot of bugs in handling filters (independent of the G’MIC stuff I am working on) and a lot of features of the plugin/filter APIs are not properly implemented. But I managed to get my generic G’MIC plugin running in there now with an input text field, although it looks horribly squished on the UI (see screenshot).
Automating parameters also works in Kdenlive now, with the simple blur here automated from 0 to 20 over the length of the video. Render time was surprisingly fast, almost realtime (~8s).
Here is the result:
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Tobias, I took the liberty of retweeting your progress, and a lot of people seem to be interested. What you’ve done so far is really great!
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Looking Good! Could you expand on the handling of filters issue? I can pass it on to the devs. But afaik Kdenlive uses frei0r through MLT, does Shotcut handle it better?
That is fast indeed!
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Cool, thanks!
Both hosts I tested (Kdenlive and Shotcut) support several different filter/plugin APIs through various wrappers, but it all seems quite convoluted and unnecessarily error prone.
frei0r ist one of the main APIs to write C++ plugins (without UI interfaces in) for these hosts, but the frei0r API is intentionally kept very simple and does not cover more sophisticated constellations. It also does not offer any UI functionality at all, which would be fine as one would suspect the host would then provide a standard parameter UI for the few parameter types frei0r uses (bool, float, string, color, point). But no, neither of the hosts do that, instead they require writing your own UI in a rather simple XML text format (Kdenlive) or a very complex Qt QML description file. Even then, some of the underlying basic functionality (e.g. text input parameters) are not present in the Kdenlive XML API, and the mapping of UI parameters to plugin parameters is therefore really quirky. In my opinion, this is really the task of the host application to provide a standard interface, at least as a fallback.
So for Shotcut, I can easily put the frei0r filter to use, but I simply lack the time and expertise to write a UI QML definition file, let alone one for each of the G’MIC filters. This could of course be automated with a batch tool, but at the moment, this does not seem worth looking into for me.
As for Kdenlive’s other quirks, the whole handling of plugins is not very consistent. The sequence of the mandatory f0r_init/f0r_deinit calls for example does not always seem to be obeyed, and when exiting the program, f0r_deinit does not get called at all, preventing proper deallocation and even causing crashes.
They also do not seem to adhere to their own specification, with tags “keywords” and “keywordsdisplay” apparently not parsed.
For others the structure is really inconsistent and error-prone:
“paramlist” is an XML attribute and contains a list of values separated by semicolon, “paramlistdisplay” is an XML tag and contains a list of names separated by comma.
Parameter updates are also triggered inconsistently, while they are set on every manual frame change, on first load or when a parameter is adjusted on the same frame, the plugin sometimes does not get updated.
Since the APIs also do not have a cancel/abort flag, each time a parameter is actually sent, a full render will be triggered that can’t be aborted.
All in all, first (personal) impressions are not too good, neither about frei0r/MLT, nor about Kdenlive/Shotcut, but maybe I expect too much. Then again, having worked with commercial video and editing applications over the last 20 years, even those so-called “professional” applications regularly drive me up the wall.
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Passing on to the Kdenlive team your feedback. Cheers
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No surprise. I recently volunteered to put some videos up on Facebook. Simple task involving putting clips together. The clips were poor and different in quality and specs; naturally, I wanted to make them easier on the eyes and ears. But the more I wanted to do, the more annoyances or bugs I caught. Many of those were longstanding issues reported intermittently over the years.
Anyway, I understand that this experience is a part of FLOSS.
So I understand this sentiment. 
On a separate note, it occurred to me right away that I was missing G’MIC in the process. So I am glad that you are looking into this.
Before I hop into bed, here are some more adaptations of the G’MIC plugin for popular video editors and editing suites:
Blackmagic DaVinci Resolve (applied on a 4K video!):
Blackmagic Fusion running inside Resolve:
Magix Vegas Pro 18.0:
The Foundry Nuke:
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Kdelive doesn’t handle well projects with various frame rates… what kind of issues did you encounter? I recently did a quick 7 video series and the only issue I had was a rotoscoping bug. Do join the chat and discuss your issues the community is very welcoming. 
Every month there is a bit of progress, I wish it could go faster sometimes but it is basically one guy doing the work in his free time.
This is a game changer indeed for floss video editing.