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c++openglgtkgtk3

GTK3 OpenGL video rendering is mostly green (YUV420P)

I'm trying to render an video through OpenGL in GTK3 on linux. These Vertex and Fragment shaders were used with succes on QT. Actually all the opengl function calls are the same from working examples on Qt.

Anyone knows why? Is it possible that GLEW coordinates are different from coordinates in QT OpenGL?

The video is in YUV420P format, so that's why the fragment shader does matrix multiplication. Is it possible that my fragment coordinates are wrong?

Anyways, here's the video:

enter image description here

My Vertex Shader:

#version 130

attribute vec4 vertexIn;
attribute vec2 textureIn;
varying vec2 textureOut;
void main(void)
{
    gl_Position = vertexIn;
    textureOut = textureIn;
}

My Fragment Shader:

#version 130 

varying vec2 textureOut;
uniform sampler2D tex_y;
uniform sampler2D tex_u;
uniform sampler2D tex_v;
void main(void)
{
    vec3 yuv;
    vec3 rgb;
    yuv.x = texture2D(tex_y, textureOut).r;
    yuv.y = texture2D(tex_u, textureOut).r - 0.5;
    yuv.z = texture2D(tex_v, textureOut).r - 0.5;
    rgb = mat3(1.0, 1.0, 1.0,
        0.0, -0.39465, 2.03211,
        1.13983, -0.58060, 0.0) * yuv;
    gl_FragColor = vec4(rgb, 1.0);
}

My rendering code:

static const GLfloat ver[] = {
    -1.0f,-1.0f,
     1.0f,-1.0f,
    -1.0f, 1.0f,
     1.0f, 1.0f
};


static const GLfloat tex[] = {
    0.0f, 1.0f,
    1.0f, 1.0f,
    0.0f, 0.0f,
    1.0f, 0.0f
};

void OpenGLArea::init()
{
    std::cout << "OpenGLArea init" << std::endl;

    set_size_request(640, 360);
    Singleton::instance()->getStream("cam1").mediaStream->ffmpegDecoder->setVideoReceiver(this);
}

void OpenGLArea::receiveVideo(unsigned char **videoBuffer, int frameWidth, int frameHeight)
{
    this->frameWidth = frameWidth;
    this->frameHeight = frameHeight;
    //Before first render, datas pointer isn't even created yet
    if (!firstFrameReceived)
    {
        buffer[0] = new unsigned char[frameWidth * frameHeight];     //Y
        buffer[1] = new unsigned char[frameWidth * frameHeight / 4]; //U
        buffer[2] = new unsigned char[frameWidth * frameHeight / 4]; //V
        firstFrameReceived = true;
    }
    else
    {
        memcpy(buffer[0], videoBuffer[0], frameWidth * frameHeight);
        memcpy(buffer[1], videoBuffer[1], frameWidth * frameHeight / 4);
        memcpy(buffer[2], videoBuffer[2], frameWidth * frameHeight / 4);
    }
    //glDraw();
}

void OpenGLArea::glInit()
{
    int frameWidth = 640;
    int frameHeight = 360;
    glClearColor(0.0f, 0.0f, 0.4f, 0.0f);

    Shader vertex_shader(ShaderType::Vertex, "vertex.shader");
    Shader fragment_shader(ShaderType::Fragment, "fragment.shader");

    program = new Program();
    program->attach_shader(vertex_shader);
    program->attach_shader(fragment_shader);
    program->link();

    glGenTextures(3, texs);//TODO: delete texture

    //Y
    glBindTexture(GL_TEXTURE_2D, texs[0]);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RED, frameWidth, frameHeight, 0, GL_RED, GL_UNSIGNED_BYTE, 0);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    //U
    glBindTexture(GL_TEXTURE_2D, texs[1]);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RED, frameWidth / 2, frameHeight / 2, 0, GL_RED, GL_UNSIGNED_BYTE, 0);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    //V
    glBindTexture(GL_TEXTURE_2D, texs[2]);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RED, frameWidth / 2, frameHeight / 2, 0, GL_RED, GL_UNSIGNED_BYTE, 0);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);

}

void OpenGLArea::glDraw()
{
    program->use();

    glVertexAttribPointer(A_VER, 2, GL_FLOAT, 0, 0, ver);
    glEnableVertexAttribArray(A_VER);

    glVertexAttribPointer(T_VER, 2, GL_FLOAT, 0, 0, tex);
    glEnableVertexAttribArray(T_VER);

    unis[0] = glGetAttribLocation(program->get_id(), "tex_y");
    unis[1] = glGetAttribLocation(program->get_id(), "tex_u");
    unis[2] = glGetAttribLocation(program->get_id(), "tex_v");

    glActiveTexture(GL_TEXTURE0);
    glBindTexture(GL_TEXTURE_2D, texs[0]);
    glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, frameWidth, frameHeight, GL_RED, GL_UNSIGNED_BYTE, buffer[0]);
    glUniform1i(unis[0], 0);

    glActiveTexture(GL_TEXTURE0 + 1);
    glBindTexture(GL_TEXTURE_2D, texs[1]);
    glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, frameWidth / 2, frameHeight / 2, GL_RED, GL_UNSIGNED_BYTE, buffer[1]);
    glUniform1i(unis[1], 1);

    glActiveTexture(GL_TEXTURE0 + 2);
    glBindTexture(GL_TEXTURE_2D, texs[2]);
    glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, frameWidth / 2, frameHeight / 2, GL_RED, GL_UNSIGNED_BYTE, buffer[2]);
    glUniform1i(unis[2], 2);

    glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);


}

class GLWindow : public Gtk::Window
{
  public:
    GLWindow()
    {

        vbox = new Gtk::VBox;
        drawing_area = new OpenGLArea();

        vbox->pack_start(*drawing_area, true, true);
        add(*vbox);
    }

  private:
    Gtk::Button *button;
    Gtk::VBox *vbox;
    OpenGLArea *drawing_area;
};

Also, I'm only getting image updates when I resize or refocus on the screen. It's possible that I'm forgetting to call some function when the video is updated. Anyone knows which function is this?

ps: OpenGLArea is subclass of Gtk::DrawingArea

UPDATE:

I just noticed that in the lines

unis[0] = glGetAttribLocation(program->get_id(), "tex_y");
unis[1] = glGetAttribLocation(program->get_id(), "tex_u");
unis[2] = glGetAttribLocation(program->get_id(), "tex_v");

unis[i] always have the same value: 4294967295, so glGetAttribLocation isn't returning anything

Solution

  • GLEW is a library that is used for retrieving the function pointers to OpenGL functions. It's needed for OGL version > 1.1.

    So, don't think of Glew as the culprit of your vertices issue. If you need to change the order of vertices is due to Winding order.
    The order also may be the cause of drawing a texture upside-down.

    glGetAttribLocation is used for attributes. In your VS these are vertexIn and textureIn.
    For uniforms (your tex_XXX) you must use glGetUniformLocation

    For the resizing issue, this question may be useful. In short, you must connect a callback for the "configure-event" and use glViewport