[mythtv-users] Tuner cards that do HD?

[R. G. Newbury]

Alex Malinovich wrote:
> On Mon, 2007-04-16 at 04:26 -0600, Brian Wood wrote:
> --snip--
>> The "important detail" you might be missing is the fact that the HDHR  
>> can't receive analog transmissions, only ATSC and unencrypted QAM.
>>
>> Not that it isn't a great device IMHO, but I think your original post  
>> mentioned analog.
> 
> I'm afraid I don't know nearly as much as I should about TV broadcasts,
> but here's what I do know. I have a plain old coax connection going into
> my TV (so no cablebox anywhere in my apt) and I can watch all of the
> basic cable channels as well as about a dozen HD channels. The HD
> channels show up as subchannels of the respective channel.
> 
> So channel 6 standard, shows up as 6-1 HD, 8 standard is 8-1 HD, etc. I
> also have a block of about 20-30 digital channels in the 70-something
> range that I'm guessing are probably used for digital cable related
> stuff like on-demand and the such.
> 
> (Pardon my ignorance of all things HD here)
> So does the cable actually have two completely different signals coming
> across? One for standard and one for HD, or are the standard channels
> just coming across as "low-quality" HD?
> 
> Normally I'd be just fine with only having the HD channels, but my
> favorite channel is Discovery and Comcast most definitely doesn't
> provide Discovery HD as part of basic cable. :) I'm just wondering if
> there's a possibility that the standard channel might be coming to me on
> the wire in some sort of digital format that the HDHR could still pick
> up or if I'd be left without it.

Guess it's time to repeat this:

There are 2 basic ways of delivering tv broadcasts: analog or digital.
There are 2 levels of definition: standard and high.
Analog broadcasts (NTSC) are always standard definition.
Digital broadcasts (ATSC) can be either standard definition or high 
definition.
(In addition, digital broadcasts can be poured down a wire or broadcast 
over-the-air. The former is generally encoded as QAM256 in North 
America. The latter is generally 8-VSM (that does NOT look right!).)

So you are probably watching the 6 channel and 8 channel as NTSC (analog 
SD) and the 6-1 and 8-1 as ATSC HD. You may, or may not, be getting 
Discovery in a digital form on one of those #70 channels. But since you 
are watching the 8-1 in HD, HOW are you watching it? You MUST have some 
form of ATSC tuner to get that. Can you not use that tuner to tune to 
channel 70 or whatever?

And note that channel '70' may well be a virtual channel: that is, an 
arbitrary number used by Comcast to designate this particular digital 
stream. The stream may well be broadcast on 'real' channel 64, stream 
pid (serviceid) 1701...

Geoff





-- 
              R. Geoffrey Newbury			
       Helping with the HTTP issue
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