On Tue, Apr 15, 2014 at 3:24 PM, Hart, James <
james.h...@schneider-electric.com> wrote:
> I’m investigating MLT as an automated video authoring tool for an
> enterprise system. So far it looks very promising, but I’d like some
> guidance with a few outstanding items.
>
>
>
> One thing that is almost non-negotiable is the use of this framework on
> windows. I’ve been using the binaries prebuilt that come along with
> Shotcut. They work well, but in the long run I’d like to be able to easily
> build the core MLT library and plugins from scratch so we can contribute
> back to the community and provide custom plugins. I’ve gone through the
> process and it seems difficult to get the environment just right to build
> in windows under mingw. Due to other concerns, we can’t use cygwin.
>
We cross-compile MLT, Shotcut, and dependencies on Linux. Some notes on
this are here:
http://www.shotcut.org/bin/view/Shotcut/CrossCompile
There is also this note on Shotcut wiki about how I setup a Windows-native
environment to debug things specific to Windows. It is mainly oriented
towards developing and debugging Shotcut rather than MLT. Still, it is
possible.
http://www.shotcut.org/bin/view/Shotcut/SetupWindowsDev
> Is there an existing easy path to make changes to existing plugins without
> involving the whole build framework and configure tools in every
> developer’s windows environment?
>
One can use the cross-compile environment to create a so-called SDK build
by running the build-shotcut.sh script with the -s option (in addition to
-o Win32). It creates a zip file that you copy to Windows and extract. At
this point, one could work on a plugin by simply copying the MLT includes
and DLL libs into your own project, or make your project build setup
reference the ones in the extracted SDK. You will need to use a MinGW-based
tool chain as I think the binaries are incompatible with MSVC.
SetupWindowsDev shows how I enhance Qt Creator with Git Bash to get a
usable command line environment in addition to the IDE.
Basically, at this time there is nothing really easy to build everything on
Windows. Even our cross-compile and Windows build tips for MLT uses some
pre-built binaries for dependencies. If you can use prebuilt MLT binaries
and just work on plugins, then it is much easier. I can upload a pre-built
SDK if you want. After you make a plugin, you must copy it into proper
place for MLT and (q)melt to find it. You add a deployment step as part of
your project's build to simplify the dev-test cycle.
> If it was up to me, I’d have us use linux for development, but we still
> need an easy way to build the patches in windows with the least amount of
> headache. Right now that translates into a dedicated windows build machine
> with an automated process. Any suggestions that would make it easy for
> individual developers to contribute using windows as their primary
> development environment?
>
>
>
> Second thing, we need the ability to burn in a timestamp that reflects
> the video’s time offset relative to a given date and time. Does that
> feature exist with any of the currently available window’s plugins? This is
> a different use case than what is answered in the FAQ.
>
>
No, there is nothing that exists to compute an offset time.
> If this feature isn’t available, ideally I would like to modify an
> existing filter to support this. Given the current difficulty with the
> build framework in windows, first pass I’d like to just create a custom
> filter which can influence something like the watermark’s filter output
> each frame. This would allow me to easily create a pipeline or xml that
> can be passed to qmelt. Is there an existing filter service which
> overlays text that I can influence some text property every frame with a
> custom filter placed before it? It seems like a simple enough use case,
> but it is unclear to me with the existing doc’s if I can influence
> something like that every single frame with any existing service. Any
> suggestions?
>
You can use dynamictext, which prioritizes qtext over pango. It might be as
simple as adding a property to dynamictext to set the base date/time and a
new substitution keyword to compute a time based on base time, frame
number, and frame rate.
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