[mythtv-users] All my unencrypted HD channels are in the 700s. Can Myth tune that high?

William Munson william_munson at bellsouth.net
Sun Sep 16 20:58:32 UTC 2007

Matt Emmott wrote:
> On 9/16/07, *Daniel Kristjansson* <danielk at cuymedia.net 
> <mailto:danielk at cuymedia.net>> wrote:
>     On Sun, 2007-09-16 at 15:02 -0400, Matt Emmott wrote:
>     > I have Charter cable tv. I just picked up a QAM capable TV, but it
>     > doesn't tune past channel 114.5. All my HD channels like ESPNHD,
>     > ABCHD, etc, are up around channel 700. I am assuming that these are
>     > unencrypted since they are non premium channels - Please correct
>     me if
>     > I'm wrong.
>     You may be wrong, the cable operator is only required to offer over
>     the air channels in the clear. Some offer all their regular package
>     channels in the clear but encrypt them in their STB, others encrypt
>     everything they can and decrypt them for you in the STB. And at least
>     one person has reported that their cable operator says they will only
>     allow "encryption to the screen TV sets" made by members of the 5C
>     cartel in the last few years (which violates at least a dozen federal
>     laws).
> A quick check of Charter shows that WGBH-HD is 782,  WBZ (CBS) is 784, 
> etc. One thing that's odd is that they're listed with a DT extension, 
> not HD. Is this some bastardized version of HD?
>     Also, there are no actual channels at "700". The cable operator
>     squishes
>     up to about 8 channels into the frequency for one channel and then
>     remaps the numbers so 100.1 becomes 557, 100.2 becomes 530, 100.3
>     becomes 623, etc.
> That's good to know.  We're veering off topic a bit, but has anybody 
> tuned into any  OTA HD channels at these freqs?  I get access to  some 
> On Demand stuff at 113.0 to 113.2 as well as a couple Music Choice 
> channels, but that's it.
>     > Anyways, since my TV doesn't tune that high, I was wondering if I
>     > could get to these channels via Myth and an HD card, like the pcHDTV
>     > HD-5500.
>     MythTV will scan cable channel frequencies 2 to 159 and T-7 to T-14.
>     You can extend this, if the hardware allows, by increasing the
>     US_MAX_CHAN frequency in libs/libmythtv/frequencytables.cpp. MythTV
>     will tune any frequency the hardware allows as well.
>     159 is 1005 Mhz, which is the maximum for most cable systems. But if
>     yours went up to 2000 Mhz, you could change the US_MAX_CHAN from 159
>     to 324 and MythTV would scan for TV on the additional EIA-542
>     channels.
>     If a cable operator went very much past 2000 Mhz they would need more
>     expensive cabling and equipment so this is unlikely, they would just
>     switch to the cheaper fiber to the home at that point.
> I'm going to  flag this email in the hopes that it will make more 
> sense as I learn more :-) . Thanks for the  wealth of information.
Here is a little bit more info for you. Your tv actually tunes all the 
channels that your cable company uses. The trick is that the programs 
are actually in the sub channels of that channel. So when your tv tunes 
to channel 111 for example it listens on that frequency for a digital 
stream that contains a list of the sub-channels on that freq. Then you 
can tune one of the sub-chan with the format of for example 111.6 which 
would be sub 6 of frequency (channel) 111. There can be dozens of 
standard def streams on one channel or just 2 or 3 hi def streams. 
Unfortunately with cable, the channels are rarely labeled since that 
info is contained in a special stream that that cable box understands 
and whichs then maps the 111.6 stream to channel 734 on your tv guide 
and listings. This leaves you guessing as to what is what. The other 
thing is that cable operators sometimes move sub-channels around. 
Normally thats transparent to the end user since the data in the listing 
steam changes at the same time but not with myth or even a regular tv 
with a QAM tuner.

My suggestion is to go thru each sub that you receive and watch it until 
you can identify it. Write that info down and rinse and repeat. :)

Watching ATSC tv from an antenna is much neater as everyone has to 
identify the channels and most provide a couple of days of program info 
in the data stream. Good luck getting listings from cable.


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