wined3d: Fix the odd line condition in gen_yv12_read().

dlls/wined3d/glsl_shader.c

@@ -12621,8 +12621,10 @@ static void gen_yv12_read(struct wined3d_string_buffer *buffer,
      * Don't forget to clamp the y values in into the range, otherwise we'll
      * get filtering bleeding. */
 
-    /* Read odd lines from the right side (add 0.5 to the x coordinate). */
-    shader_addline(buffer, "    if (fract(floor(texcoord.y * size.y) * 0.5 + 1.0 / 6.0) >= 0.5)\n");
+    /* Read odd lines from the right side (add 0.5 to the x coordinate). Keep
+     * in mind that each line of the chroma plane corresponds to 2 lines of the
+     * resulting image. */
+    shader_addline(buffer, "    if (fract(floor(texcoord.y * size.y) * 0.25 + 1.0 / 6.0) >= 0.5)\n");
     shader_addline(buffer, "        texcoord.x += 0.5;\n");
 
     /* Clamp, keep the half pixel origin in mind. */