Sharing EGL context with glimagesink

[Matthew Waters]

On 06/10/15 23:52, Jorge Fernandez Monteagudo wrote:
> Hi,
>
> I'm trying to share the main EGL context from my application and the glimagesink element
> from the pipeline I'm implementing, using the 'other-context' field. I'm trying to paint the
> texture with the video frame with my code.

glimagesink in 1.6 does not have an 'other-context' property anymore and
so that information needs to be provided with GstContext. See
http://ystreet00.blogspot.com.au/2015/09/gstreamer-16-and-opengl-contexts.html
for the details.

> Now I have the next vars initialized ok (I can paint using gl commands)
>
> EGLDisplay dpy;
> EGLSurface surface;
> EGLContext context;

The question is if you can actually simply use the EGLDisplay without
first going through the winsys, wayland/X11/dispmanx/etc.  Android is
the only platform that I know of that will allow using the EGLDisplay
natively without first having an existing display connection. 
Essentially you must pass the winsys display handle if you have it over
the EGLDisplay handle.

> and the 'eglMakeCurrent(dpy, surface, surface, context)' call returns success.
> Then I set up the pipeline and the glimagesink with:
>
>   GstGLDisplay *glDisplay;
>   GstGLContext *glContext;
>  ...
>
>   // Set glimagesink gl context.
>   eglMakeCurrent( dpy, EGL_NO_SURFACE, EGL_NO_SURFACE, EGL_NO_CONTEXT );
>   glDisplay = (GstGLDisplay *)gst_gl_display_egl_new_with_egl_display( dpy );
>   glContext = gst_gl_context_new_wrapped( glDisplay, (guintptr) context, GST_GL_PLATFORM_EGL, GST_GL_API_GLES1 );

Just a note that we don't actually support the GST_GL_API_GLES1 API.  If
you're actually using GLES1-only api calls I'm afraid this will not work
at all.

That should help you along the way.

Cheers
-Matt

>   g_object_set( G_OBJECT(glimagesink), "other-context", glContext, NULL );
>   eglMakeCurrent( dpy, surface, surface, context );
>   printf( "glDisplay=%p   glContext=%p\n", glDisplay, glContext );
>
> When I run the code I see the printf trace
>
> glDisplay=0x24c78   glContext=0x255848
>
> and the backtrace
>
> Program received signal SIGSEGV, Segmentation fault.
> [Switching to Thread 0x713fc460 (LWP 15929)]
> __glInitFramebufferStates (gc=gc at entry=0x37b2ec) at src/glcore/gc_es_fbo.c:998
> 998     src/glcore/gc_es_fbo.c: No such file or directory.
> (gdb) bt
> #0  __glInitFramebufferStates (gc=gc at entry=0x37b2ec) at src/glcore/gc_es_fbo.c:998
> #1  0x768cba1c in __glInitContextState (gc=gc at entry=0x37b2ec) at src/glcore/gc_es_context.c:702
> #2  0x768cc048 in __glCreateContext (clientVersion=<optimized out>, imports=0x713fbc88, sharedCtx=0x22e974) at src/glcore/gc_es_context.c:1043
> #3  0x76d1b504 in _CreateApiContext (Thread=Thread at entry=0x262204, Context=Context at entry=0x37b1cc, Config=0x1b5f0c, Config at entry=0x31be, SharedContext=0x22e974)
>     at gc_egl_context.c:593
> #4  0x76d1bdf4 in eglCreateContext (Dpy=0x1b4204, config=<optimized out>, SharedContext=0x1b77dc, attrib_list=0x713fbd6c) at gc_egl_context.c:1385
> Backtrace stopped: Cannot access memory at address 0x302a
>
>
> Any hint?
>
> Regards
>
>
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