<div dir="ltr"><div>Could you expand on 1 and 2? </div><div>This rendering code works with my single threaded application.</div><div> </div><div>Is the problem with 1 the fact that the vertices are allocated inside a function (ie on the stack)?</div><div>I have no idea what you mean by 2. Apologies for being a noob.</div><div>Re 3, does this mean gstreamer creates a separate OpenGL context? Is there a new context made for every element? Do some elements share contexts?</div><div> </div><div>Thanks </div></div> <div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Mon, Aug 2, 2021 at 3:40 AM Matthew Waters <<a href="mailto:ystreet00@gmail.com">ystreet00@gmail.com</a>> wrote: </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"> <div> Take a look at <a href="https://gitlab.freedesktop.org/gstreamer/gst-plugins-base/-/blob/master/gst-libs/gst/gl/gstglfilter.c#L1165" target="_blank">https://gitlab.freedesktop.org/gstreamer/gst-plugins-base/-/blob/master/gst-libs/gst/gl/gstglfilter.c#L1165</a>. I can notice a couple of things wrong: 1. Vertex glBufferData call is taking the address of an array that should not be taken. 2. No retrieval of the vertex attribute locations (GPU driver decides these) 3. You may not be creating the VAO in the correct thread? VAO's are not OpenGL shareable resource across OpenGL contexts. Cheers -Matt <div>On 2/8/21 5:47 am, Edward Anon via gstreamer-devel wrote: </div> <blockquote type="cite"> <div dir="ltr"> <div>My client takes a camera feed over RTP. I want to render an overlay onto it using opengl. Hence, I want to use GlImageSink in my application as it provides me with the next frame already in a texture. I want to blit the already rendered overlay onto the texture prior to rendering. </div> <div>As a first step I am writing a simple draw callback which should just render the texture to the screen. I am basing my callback on the cube example in the gst-plugins-base source.</div> <div> </div> <div>```</div> <div> <pre style="background-color:rgb(43,43,43);color:rgb(169,183,198);font-family:"JetBrains Mono",monospace;font-size:9.8pt">gboolean drawCallback (GstElement * gl_sink, GstGLContext *context, GstSample * sample, gpointer data) { assert(gl_sink); assert(context); assert(sample); assert(not data); GstVideoFrame v_frame; GstVideoInfo v_info; GstBuffer *buf = gst_sample_get_buffer (sample); GstCaps *caps = gst_sample_get_caps (sample); gst_video_info_from_caps (&v_info, caps); if (!gst_video_frame_map (&v_frame, &v_info, buf, (GstMapFlags) (GST_MAP_READ | GST_MAP_GL))) { g_warning ("Failed to map the video buffer"); return TRUE; } GLuint texture_id = *(guint *) v_frame.data[0]; Texture t; t.from(texture_id, Texture::TextureType::COLOUR); t.render(); return true; }</pre> ``` </div> <div>However, I get the following error: ```gldebug gstgldebug.c:306:_gst_gl_debug_callback:<glcontextglx0> high: GL error from API id:1, GL_INVALID_OPERATION in glDrawArrays```. </div> <div>The render code is as follows: ``` <pre style="background-color:rgb(43,43,43);color:rgb(169,183,198);font-family:"JetBrains Mono",monospace;font-size:9.8pt">if (texture_type != UNINITIALISED) { switch (texture_type) { case COLOUR: colour_shader.use(); break; </pre> <pre style="background-color:rgb(43,43,43);color:rgb(169,183,198);font-family:"JetBrains Mono",monospace;font-size:9.8pt">// other texture type setup </pre> <pre style="background-color:rgb(43,43,43);color:rgb(169,183,198);font-family:"JetBrains Mono",monospace;font-size:9.8pt"> default: throw std::runtime_error("Unsupported texture type"); } glBindVertexArray(quadVAO); glDisable(GL_DEPTH_TEST); glBindTexture(GL_TEXTURE_2D, opengl_texture); glDrawArrays(GL_TRIANGLES, 0, 6); glBindTexture(GL_TEXTURE_2D, 0); glEnable(GL_DEPTH_TEST); }</pre> ``` </div> <div>Shaders, VAO and VBO set up as follows: ``` <pre style="background-color:rgb(43,43,43);color:rgb(169,183,198);font-family:"JetBrains Mono",monospace;font-size:9.8pt"> glGenVertexArrays(1, &quadVAO); glBindVertexArray(quadVAO); glGenBuffers(1, &quadVBO); glBindBuffer(GL_ARRAY_BUFFER, quadVBO); glBindVertexArray(quadVAO); glBindBuffer(GL_ARRAY_BUFFER, quadVBO); glEnableVertexAttribArray(0); glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 4 * sizeof(float), (void *)nullptr); glEnableVertexAttribArray(1); glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 4 * sizeof(float), (void *)(2 * sizeof(float))); constexpr float quadVertices[] = { // positions // texCoords 1.0f, -1.0f, 0, 1, // top left 1.0f, 1.0f, 0, 0, // bottom left -1.0f, 1.0f, 1, 0, // bottom right 1.0f, -1.0f, 0, 1, // top left -1.0f, 1.0f, 1, 0, // bottom right -1.0f, -1.0f, 1, 1 // top right }; glBufferData(GL_ARRAY_BUFFER, sizeof(quadVertices), &quadVertices, GL_STATIC_DRAW); glBindVertexArray(0); colour_shader = Shader(shaderRoot + "quadFromTexture.vs", shaderRoot + "colourTexture.fs"); </pre> <pre style="background-color:rgb(43,43,43);color:rgb(169,183,198);font-family:"JetBrains Mono",monospace;font-size:9.8pt"> // setup other shaders</pre> ``` </div> <div>What am I doing wrong?</div> </div> </blockquote> </div> </blockquote></div>