The title of the video is probably deliberately and artificially made sensational, but the subject is explained a bit more clearly in the first post and image here -
Can your digital cable impact the sound of your system? Like most things, the answer is “maybe”… Reading some of the cable advertisements I see all kinds of claims. Some make no sense to me, such as “use of non-ferrous materials isolates your cable from the deleterious effects of the Earth’s...
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Basically, digital (square) waveform needs infinite (or at least very high) bandwidth to transmit like a square otherwise it comes out wonky and wrecks havoc for the digital waveform
interpretation. In audio it causes jitter and also interpolated (instead of actual) data.
If you look at a FFT of a 1Khz square wave you will see that its littered with 20+ harmonics. These harmonics are what make the difference between a 1Khz sine wave and 1Khz square wave. And all those harmonics including that 20th+ one have to be transmitted properly to reveal the same square wave on the receiving end. So if you want a 1Mhz square wave to look like a 1Mhz square wave on the other end of the wire (optical or coax or ethernet or even wireless) you want at least a flat 20Mhz bandwidth of the entire transmission layer (transmitter, receiver, cable etc..). because digital systems rely on the transition edge of that square wave to determine 1 or 0 or other control like for example clock ticks.
Otherwise you loose those higher harmonics and that results into not square and straight edges but bent corners and edges which if bent far enough can cause that interpretation of 1 and 0 and clock ticks to be way off than the original. This causes bandwidth-limited transmission jitter on spdif and similar transmissions methods.
http://nwavguy.blogspot.com/2011/02/jitter-does-it-matter.html (scroll down to cable jitter section and see the image for it).
edit: and btw, before usb asynchronous came out it was usb isochronous and probably some devices still use it, but it was a complete disaster in terms of jitter due to this reason. because loss of data in data transmission over usb or ethernet can be detected and resolved on the fly but there is no room for such correction for real-time audio data. That is why it works great for transmitting GoBs of data but not realtime audio, and worse, from which a clock needs to be recovered.
and here's a nice animation demonstrating the high number of harmonics that need to be passed in order to preserve a good square form -