Write an Overlay Shader

Beginner here. Need some help writing a simple overlay shader to overlay image on top of video feed.

Here’s what I have so far:

And to use the shader:

buffer.begin();
dst.draw(0, 0);
overlayShader.begin();
overlayShader.setUniformTexture(“src”, srcBlur, 1);
overlayShader.setUniformTexture(“dst”, dstBlur, 2);
dst.draw(0, 0);
overlayShader.end();
buffer.end();

What am I doing wrong? I can see the live video feed but no image on top.

Thanks much,