Cables

[Aussman]

I was wondering if anyone could explain why do we need hdmi, optical or coaxial cables, when a cheap $2 RF cable can carry a digital signal from our antennaes to our tv which contains 20 odd channels all with digital sound and some with HD content - much higher total bandwidth than an HDMI is rated to carry

[momaw]

I was wondering if anyone could explain why do we need hdmi, optical or coaxial cables, when a cheap $2 RF cable can carry a digital signal from our antennaes to our tv which contains 20 odd channels all with digital sound and some with HD content - much higher total bandwidth than an HDMI is rated to carry

Go for it.

[rowanr]

to me thats kind of like asking why we need to plug in to a power source for our TVs when the old school ham radios were powered from the radio waves.

[Aussman]

to me thats kind of like asking why we need to plug in to a power source for our TVs when the old school ham radios were powered from the radio waves.

i think its different tv signal you watch is coming through rf cable why can't blu ray dvd etc? can someone who knows explain. It may be a stupid question but I was just interested

[sten1503561342]

Its all about Bandwidth brother.

[Aussman]

Its all about Bandwidth brother.

but the bandwidth must be huge on RF to accomodate channels 9,7,10,2,sbs multiple channles on each and audio tracks all simultaneously not sure but would be massive to have 2-3 HD channles simultaneously with DD

[momaw]

but the bandwidth must be huge on RF to accomodate channels 9,7,10,2,sbs multiple channles on each and audio tracks all simultaneously not sure but would be massive to have 2-3 HD channles simultaneously with DD

All filled with glorious compression artifacts.

[joz]

Well you could try and experience the dissapointment first hand I suppose.

But in a way its a fair question in that it all just travels along your good o'l RG6 from that clothes hoist on the roof until its decoded,then you need voodoo cable and electronics?

I'd say its all done due to copy protection of the HD stuff.

Edited December 2, 2008 by the joz

[lordvader1503559690]

RF cable (and coaxes in general) have HUGE bandwidth, especially when it comes to digital signals, BUT, are not HDCP compliant, and no one likes to use existing tech, when you can lock everyone into something new and shiny

[Aussman]

RF cable (and coaxes in general) have HUGE bandwidth, especially when it comes to digital signals, BUT, are not HDCP compliant, and no one likes to use existing tech, when you can lock everyone into something new and shiny

so its just becasue of copy protection?

I guess telling Hardly normal drones that a $2 RF cable can carry tv signal as well as $300 monster should shut em up wait they'll probably start selling $200 RF cables

[joz]

RF cable (and coaxes in general) have HUGE bandwidth, especially when it comes to digital signals, BUT, are not HDCP compliant, and no one likes to use existing tech, when you can lock everyone into something new and shiny

I suppose thats what I was getting at too.

I mean at home we have cable broadband and cable tv.All that stuff and more can travel downthat wire going both ways.Then you have all the people in your neighbourhood all sharing that same cable of the street.

But the clincher is the decoding side of that jumble of signals.

And yep its all copy prtoction.

Not only for the studios but for the service providers aswell.

[flukeyluke]

Bandwidth is the big thing.

Your neighbours might appreciate you trying though

I am old school, and would use a good cable over good wireless anyday.

[joz]

so its just becasue of copy protection?

I guess telling Hardly normal drones that a $2 RF cable can carry tv signal as well as $300 monster should shut em up wait they'll probably start selling $200 RF cables

Yes but the manufacturers have specced specific cables that allow components to talk to each other and how they do it..(scums)

[CAVX]

If you were to use RF, you would need to modulate the signal at the source, apply the right amount of compression) and then decode the signal at the other end. Given most of us have our player and our display within 10m, a direct connection has to be better(?). Also as mentioned - copy protection for HD content. If the signal was "RF" what is stopping the house next door or down the street tuning in as well?

AC3 on LD was an example where they used RF modulation (hence the name AC3-RF) to store a digital signal in the space on the disc that was previously only for analogue L and R audio - it could now store 5.1DD in the right channel and still gave the choice for a running audio commentry in the right (or is the other way around?)...

Mark

[Aussman]

weren't they able to do macrovision over rf for VHS ie when you tried to copy from one VHS to another you got a blue picture

[flukeyluke]

I suspect there would also be latency issues which would be frustrating

[alanh]

Aussman,

Now for the real reason.

Firstly HDMI is 3 circuits of 8 wires. One circuit for the luminance signal and another for the colouring signals. These signals remain in their uncompressed digital form. The third circuit operates in the reverse direction so that your TV remote control can switch on and control other devices such as Blu-ray players and sound amplifiers.

The HDMI interface also carries the signal characteristics such as the number of frame/s, and the number of pixels. It is true it also carries the encryption information which is usually only applied to 1920 x 1080 @ 24 frame/s progressive. This is to ensure that the producers of the programs get some of their production costs back.

If you wished to use RF cable you would have to spend considerably more modulating 2 very high bandwidth signals and then have a specific high bandwidth additional receiver. If you wanted to use a standard receiver you would have to MPEG encode the signal which is very expensive to do properly.

So in summary, this is the best and cheapest way of interconnecting video & audio between domestic devices.

AlanH

[sol381]

heres something i read on the QED website.

When we say rather quickly, perhaps we’re understating that a bit too much. HDMI is currently specified to carry up to 10.2 Giga bits of uncompressed video, multi-flavoured audio and control signals every second. That’s the equivalent of 700 simultaneous HDTV broadcasts, 1,000 parallel high-speed broadband connections or the music from 7,500 CD players side by side, all playing at once. So actually, it’s very fast indeed.

[dax]

Its not so much about bandwidth - its about having a standard.

The standard that was picked (hdmi) offers big advantages over a rf encode/decode, both in terms of features but also for how cheap/easy it is to implement.