OpenGL ES and large textures

[bunjee207]

Greetings Qt enthusiasts,

I'm on Windows 10 with Qt 5.11.1.

I'm building this video browser with Qt + libVLC and recently switched to the OpenGL ES backend:

QCoreApplication::setAttribute(Qt::AA_UseOpenGLES);

Coming from the Desktop OpenGL backend I immediately noticed how faster it was at resizing windows, and it felt like the proper way to go.

Unfortunately when playing a 1440p video the CPU usage increases and the rendering gets slower, like way slower than classic OpenGL. Is there a flag or some configuration to alter OpenGL ES behavior with larger textures that update frequently.

PS: my player is based on vertex and fragment shaders for rendering (https://github.com/omega-gg/Sky/blob/master/src/SkMedia/src/media/WBackendVlc.cpp#L371).

[bunjee207]

For the record here are the shaders I'm currently using:

/* virtual */ const char * WBackendVlcShader::vertexShader() const
{
    return "#version 100\n"

           "attribute highp vec4 vertex;"
           "attribute highp vec2 fragment;"

           "uniform highp mat4 position;"

           "varying highp vec2 vector;"

           "void main()"
           "{"
               "gl_Position = position * vertex;"

               "vector = fragment;"
           "}";
}

/* virtual */ const char * WBackendVlcShader::fragmentShader() const
{
    return "#version 100\n"

           "uniform sampler2D y;"
           "uniform sampler2D u;"
           "uniform sampler2D v;"

           "uniform mediump mat4 matrix;"

           "varying highp vec2 vector;"

           "uniform lowp float opacity;"

           "void main()"
           "{"
               "highp vec4 color = vec4(texture2D(y, vector.st).r,"
                                       "texture2D(u, vector.st).r,"
                                       "texture2D(v, vector.st).r, 1.0);"

               "gl_FragColor = matrix * color * opacity;"
           "}";
}