How does composite or coaxial use just one wire while HDMI or SCART need a ton on them


How does composite or coaxial use just one wire while HDMI or SCART need a ton on them

In: Technology

Co-axial is 2 wires, the middle is a solid core, that’s wrapped in some plastic/rubber and then there is a woven wire wrapping that, then another coating of plastic insulation. HDMI needs several wires because there are several different signals being sent.

On Coax you had a mix of video and audio signal, but no way to convey any other information.

With SCART you gained the ability to send audio and video on separate channels, as well as daisy-chaining multiple devices and have the sending device convey the requested aspect ratio.

And finaly in HDMI you have the video and audio data in much higher definition, back channels so that for example your TV remote can control the Bluray player, chaining of devices, … Also, about half of the pins connect to just the opposite wire for a twisted pair which helps reduce noise and increase data rates (again so you can watch in 4K instead of 576i (PAL) / 480i (NTSC))

If you want to transmit more data (higher resolution) and more different kinds of data (back channels, Sound, Control channel) you eventually reach a point where it is simpler to split the data across multiple wires and pins than to come up with a system that would allow everything on one wire, if that’s physically possible at all.

The signal sent over composite or coax is the same one used for analog TV transmission in the old days. Remember what the quality was like?

You actually have two wires in composite or coax, the outer one is shaped as a circle around the inner one. These are radio waves and that’s how you send radio waves with minimum interference and without letting them leak out of the cable.

Nowadays it’s digital, at super duper high resolutions and framerates and still crystal clear. The shape of the cable is less important, so we can pack more wires in to get even more pixels across.

As for SCART, all the wires have separate functions. There’s stuff like audio in AND out, both left and right, that’s 4 wires already. Composite AND RGB video with a separate shield for each – that’s 8 pins. One of them even carries the video signal the TV is receiving from its antenna, so you don’t need a separate antenna system if you have some kind of encrypted pay service.