Android drawing texture with OpenGL ES 2.0 slow on some devices

Question

In my Android 4.3 application, I would like to load a texture from a local png onto a TextureView. I do not know OpenGL and I am using the code from the GLTextureActivity hardware acceleration test. I am pasting also the loading texture part here:

    private int loadTexture(int resource) {
        int[] textures = new int[1];

        glActiveTexture(GL_TEXTURE0);
        glGenTextures(1, textures, 0);
        checkGlError();

        int texture = textures[0];
        glBindTexture(GL_TEXTURE_2D, texture);
        checkGlError();

        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);

        Bitmap bitmap = BitmapFactory.decodeResource(mResources, resource);

        GLUtils.texImage2D(GL_TEXTURE_2D, 0, GL_RGBA, bitmap, GL_UNSIGNED_BYTE, 0);
        checkGlError();

        bitmap.recycle();

        return texture;
    }

I am running the code in two devices: Nexus 7 and Galaxy Nexus phone, and I notice a huge speed difference between the two. For Nexus 7, the drawing part takes about 170 ms, although for the Galaxy Nexus it takes 459 ms. The most time consuming operation is the loading of the texture and especially the texImage2D call. I have read that there are devices with chips that are slow on texImage2D-texSubImage2D functions but how can someone tell which are those devices and how can I avoid to use those functions to achieve the same result?

Thank you in advance.

// EDIT: the glDrawArrays(GL_TRIANGLE_STRIP, 0, 4) call seems to also be significantly slower in the phone device. Why is this happening? How could I avoid it?

Answer 1

Are you loading textures on each frame redraw? That's just not right - you should load textures only once before main rendering loop. You won't get instant textures loading even on the fastest possible device - you load resource, decode bitmap from it and then load it to GPU. This takes some time.