Pin functions can vary by LCD panel manufacturer (AUO, Innolux, etc.). Always check the specific datasheet for your IN518 marking and package.
(e.g., "LA-A994P schematic") rather than just the IC part number often yields the full pinout. Visual Inspection inx in518 ic pinout diagram top
If you'd like, I can help you (like a model number) this IC is in to find a more precise circuit diagram. AN5265 Audio IC Datasheet Overview | PDF - Scribd Pin functions can vary by LCD panel manufacturer