From a multimedia perspective GLES >= 2 has the big advantage of
supporting external textures (`OES_EGL_image_external` /
`OES_EGL_image_external_essl3`), allowing various YUV formats to be
imported directly by drivers.
It appears unlikely by now that the extension will ever be ported to
GL with Vulkan becoming more popular, leaving GL without an "official"
way to import YUV formats.
Further more, for Gst internal purposes it's likely that GLES2 works
equally well if not better on most drivers these days, especially on
embedded devices.
Thus switch the default for EGL context creation to GLES2. This won't
affect apps that create their own context, but `gst-launch-1.0` etc.,
which are often used for testing so people don't have to pass
`GST_GL_API=gles2`.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/5509>
By calling the internal function gst_gl_context_egl_fetch_dma_formats() the an
array of structures holding a DMA fourcc format and its modifiers (another array of
structure holing modifier and if it's external only) will be stored.
Users would call gst_gl_context_egl_get_format_modifiers() to get the array of
modifiers of a specific DMA fourcc format.
Co-authored-by: He Junyan <junyan.he@intel.com>
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/4680>
