We recently had a comment on an article about how HDMI works. Or should we say "works?" Because it doesn't work for many. If you disable CEC and don't need eARC, it works fine. But how are you going to get your audio from the apps in your TV back to your AV receiver? HDMI eARC is the only way to get lossless audio. But why? Why can't an optical cable send full lossless audio? The answer is both simple and dumb. And it should make you mad. Let's discuss.
HDMI Marketing Hype
If you listen to the HDMI people, they'd have you believe that their cable is the only one capable of sending lossless audio. They also claim that their solution is the best for other reasons. Let's break down a couple.
Single Cable Solution
One of the big "advantages" of HDMI is that it is a single cable solution. At least that's what they tell you. With a single HDMI connection, you can send video and audio. With ARC and eARC, you can send audio back to your AV receiver from your TV. There was even the (mostly unrealized) promise that you could use the HDMI cable to connect all your devices to the Internet. That feature was never widely adopted and therefore never worked.
Before HDMI, we often had multiple cables for video (component video) and even more for audio. TOSLink (commonly referred to as optical these days) and coaxial digital cable simplified audio down to one cable for audio but we were still stuck with three additional cables for video.
Fiber Optic Cable Bandwidth
HDMI marketing would have you believe that the optical cable is not capable of sending full lossless audio back to your AV receiver. These are the same people that will sell you an optical cable for long HDMI runs. Fiber optic cables bring high-speed Internet to your home. They are used in runs far too long for traditional copper. The cable isn't the problem.
HDMI Killed the Potential of Optical
When HDMI hit the scene, it promised HDCP. HDCP or High-bandwidth Digital Copy Protection is designed to stop piracy. If you've ever heard anyone talk about the HDMI "handshake," they are talking about HDCP. HDCP verifies that each end of the HDMI cable is connected to an authorized device. At the same time, it checks the capabilities of each device (often leading to connection issues).
This was far too attractive to content creators.