[Kdenlive-devel] movit in kdenlive build script

Dan Dennedy dan at dennedy.org
Sun Mar 16 17:16:09 UTC 2014

On Sat, Mar 15, 2014 at 9:49 AM, Steinar H. Gunderson <
sgunderson at bigfoot.com> wrote:

> On Sat, Mar 15, 2014 at 09:40:46AM -0700, Brian Matherly wrote:
> > Sorry, I was off by a digit. I should have said that my laptop suports
> 3.1
> > but Shotcut requires 3.2 to use movit filters.
> I don't know offhand what this requirement is for. Maybe GL_ARB_sync (I
> added
> a dependency on this to MLT at some point, but it would be relatively easy
> to
> add back the glFinish() fallback if somehow there are important cards that
> don't support this), but you don't need the rest of 3.2 for that. In any
> case, I'm running Kdenlive with Movit just fine with my 5th gen Intel
> (OpenGL 2.1 + extensions), so I don't think you have to worry about this
> for
> Kdenlive.
There are 2 reasons for GL v3.2. The first one is a soft requirement - a
simple way to specify what is needed without requiring one to be very
knowledgable about GL extensions. Yes, the sync extension is being used,
which was added in v3.2, thus the reason for stating that.

The second reason creates a hard requirement on Windows only and might be
due to how Qt 5 works, but I am not sure. On my Windows systems, in order
to get GL to accept the usage of this and other extensions, upon requesting
a context through Qt, I must specify a GL version that is high enough. So,
on Windows, at least on my systems, I must request 3.2. This is not done on
Linux and OS X. On those platforms, Qt creates a context, verifies
extensions, and sets up function pointers suitable for a common subset of
OpenGL 2.0 and GLES 2.0 for Qt Quick per its default behavior. The context
is not limited to those GL versions, usage of extensions work fine, and
there is no coded dependency on a specific GL version in Shotcut or MLT.

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