-uniform sampler2D PREFIX(tex_y);
-uniform sampler2D PREFIX(tex_cb);
-uniform sampler2D PREFIX(tex_cr);
+// Implicit uniforms:
+// uniform sampler2D PREFIX(tex_y);
+// uniform sampler2D PREFIX(tex_cb);
+// uniform sampler2D PREFIX(tex_cr);
vec4 FUNCNAME(vec2 tc) {
// OpenGL's origin is bottom-left, but most graphics software assumes