Here’s a deep review of , explaining what it is, how it works, when you should use it, and its limitations. 1. What Is Realtek Digital Output? Realtek Digital Output is not a physical device — it’s a software-based audio endpoint that appears in Windows (or other OS) when you have a Realtek audio codec chip on your motherboard or sound card. It represents the S/PDIF (Sony/Philips Digital Interface) output capability of your system.