What better, coax or HDMI?

[Raiders Army]

No seriously, what's better? We were talking at work today and I brought up the point that I get HD channels over an off-air antenna as well as my DirecTV box. My TV is older, so it's HD-Ready and doesn't have HDMI inputs. The signal goes through a coax cable from my off-air antenna and DirecTV satellite receiver via coax into my HD-DVR box. My box is connected to my TV via component cables.

From what I understand in terms of picture, coax is the worst connection, composite cables are better, S-Video is better, component cables are better, and HDMI is the best. I'm not sure where DVI falls in there, but regardless supposedly HDMI is the best connection and thusly the most costly. My question is that if the signal is only as good as the lowest "carrier", why wouldn't a coax cable be sufficient to provide High-Def channels to my TV? Is the HDMI cable "upconverting" the picture somehow? I would think that if I had a HDTV instead of a HD-Ready TV I could connect the off-air antenna to my TV via a coax and still get a 1080i picture.

[Easy Mac]

hdmi

[cartman]

Your DirecTV box is doing the converting. The format of the signal as it comes across the coax is not viewable, it is basically a digital transmission, much as a cable modem operates. The DirecTV receiver takes this transmission and converts it into a viewable format. It is at that point the quality of the connection to the TV comes into play.

[Raiders Army]

But in the case of HDTVs, wouldn't a coax connection be sufficient since the conversion to a viewable format is done within the TV?

[cartman]

Originally Posted by Raiders Army

But in the case of HDTVs, wouldn't a coax connection be sufficient since the conversion to a viewable format is done within the TV?

No, since the signal has already been converted. The TV would have to have a DirecTV converter inside for that to work. The TV with a built-in HDTV converter is expecting raw transmission over the coax connection, not the already converted output from the DirecTV box.

[CU Tiger]

HDMI =


Coax =


well for som reason I cant get pics to work, so

hdmi = http://images.google.com/imgres?imgu...006-14,DVXA:en

coax = http://images.google.com/imgres?imgu...006-14,DVXA:en

[CU Tiger]

Originally Posted by cartman

No, since the signal has already been converted. The TV would have to have a DirecTV converter inside for that to work. The TV with a built-in HDTV converter is expecting raw transmission over the coax connection, not the already converted output from the DirecTV box.

Exactly, with satellitte it is a digital image message , that the box converts to an image.

With a built in HD converter, a HD cable coax would be fine, but the satelitte signal is "coded " or encrypted so that your TV wont interpret it....for now.

That will be changing very soon

[Daimyo]

If your TV has a built in HD converter (such as for QAM or OTA) you don't lose anything on the coax because it is just a digital signal that your box or TV is decoding. Coax has a very high bandwidth for digital signals.

What you want to avoid is sending an already decoded signal through coax (such as hooking your cable or satellite box to your TV with coax).

[stevew]

This is what I don't get, and perhaps someone could explain it better. Essentially with the HD ATSC/QAM tuners that are out now, wouldn't it be theoretically possible NOT to even need this cable infastructure that is out there? Seemingly all a company would need to do is build a few digital broadcasting towers, and people could decipher the digital signals over the air w/ a simple antenna. It may not be feasible for one location to send out 100+ digital signals, which could be what's holding it back. The other thing I considered is that then the cable company would not have a way to charge for it's services.

[SteveMax58]

Originally Posted by stevew

This is what I don't get, and perhaps someone could explain it better. Essentially with the HD ATSC/QAM tuners that are out now, wouldn't it be theoretically possible NOT to even need this cable infastructure that is out there? Seemingly all a company would need to do is build a few digital broadcasting towers, and people could decipher the digital signals over the air w/ a simple antenna. It may not be feasible for one location to send out 100+ digital signals, which could be what's holding it back. The other thing I considered is that then the cable company would not have a way to charge for it's services.

Off-Air RF spectrum is the biggest issue here. If you've ever seen an MMDS cable system, this was essentially the death of them...some do still exist, but they are fundamentally incapable of competing with modern US CATV companies. The Off Air spectrum is far more limited (by regulation) than what you can put over a fiber or other private network.

Currently, the FCC is trying to help recover some of this spectrum by enforcing the broadcast digital deadlines for OTA & Satellite...but for the OTA portion, it's really not going to free up enough to do something like what your talking about.

[SteveMax58]

Originally Posted by Raiders Army

But in the case of HDTVs, wouldn't a coax connection be sufficient since the conversion to a viewable format is done within the TV?

There are 2 parts to this, as it relates to the consumer's house.

1) Coax, in the case of Satellite RF(DirecTV) is used to transport RF carriers (signals) to the satellite receiver. These signals are tranported at a frequency range which your TV was not designed to decode(i.e. tune to). So it is incomparable to measure it to HDMI in this scenario...as they are both doing something different here.

If you use an OTA antenna to pickup local channels...you are tranporting signals which ARE meant to be tuned to by your TV. You could hook this directly to your TV, or hook into your DirecTV Rx if it supports it.

2) In the case of CATV...coax is again transporting signals, but in this scenario it is within the frequency range of your TV's decoding (tuning) capability(I'm referring to a high end HDTV here).

Here you can use Cablecard(if supported) to merely decrypt the signals, then use your TV to decode(tune/view) them. Or the more popular way is to use a Settop Box(STB) to decrypt & decode, and send the decoded signal to your TV. HDMI is an exceptional way to transport this signal, as are component cables...and yes coax is also just fine, but it is actually remodulating it to a frequency range your TV will accept (i.e. channel 3, 4) so your TV will need to decode the signal. In any transmission, the less times you must decode the same signal, the better in theory.

However, malfunctioning cables aside, the average consumer(and even the above average consumer) does not typically understand what they are looking at when they determine "which setup looks better?". They often confuse source content, incomparable source resolutions & the like. That doesnt mean under strict conditions most couldnt be told the difference & notice, it's just very uncommon for people to properly identify "what affect THEY really had" on the picture they are viewing.

[gstelmack]

Originally Posted by stevew

This is what I don't get, and perhaps someone could explain it better. Essentially with the HD ATSC/QAM tuners that are out now, wouldn't it be theoretically possible NOT to even need this cable infastructure that is out there? Seemingly all a company would need to do is build a few digital broadcasting towers, and people could decipher the digital signals over the air w/ a simple antenna. It may not be feasible for one location to send out 100+ digital signals, which could be what's holding it back. The other thing I considered is that then the cable company would not have a way to charge for it's services.

There was a company out there attempting just that. The name escapes me at the moment, but keep in mind that getting good signals from an antenna can be just as challenging as getting a good signal from satellite. For example, I live in a low point between two sort-of-hills, and it's much easier for me to point a dish over the trees than it is to get my antenna to pull in all my locals.