[mythtv-users] External Channel Change Script for DVB cards

Colin Albert colintrebla at gmail.com
Mon Oct 31 15:41:51 UTC 2011

On 10/30/2011 01:12 PM, Raymond Wagner wrote:
> On 10/30/2011 12:58, Mike Perkins wrote:
>> On 30/10/11 12:25, Raymond Wagner wrote:
>>> On 10/30/2011 08:11, Colin Albert wrote:
>>>> On 10/29/2011 11:29 AM, Devin Heitmueller wrote:
>>>>> On Sat, Oct 29, 2011 at 10:39 AM, Colin Albert<colintrebla at gmail.com>    wrote:
>>>>>> I am reviving and old thread.  It relates to an issue that is a problem for
>>>>>> me and will be an ever increasing problem as Cable companies continue to
>>>>>> adopt SDV.
>>>>>> The problem: I have a QAM card and want to build a MythTV box instead of
>>>>>> using the cable company's (busted/worthless) DVR. The cable company uses
>>>>>> SDV, so QAM is limited to OTA locals.
>>>>>> My solution: get a set top box from the cable company, hook it to my
>>>>>> MythTV.  Use a External channel change script to change channels so that the
>>>>>> box is requesting the channel that I want. Then change the channel on the
>>>>>> QAM card to that channel.
>>>>> This won't work.  The RF output on the set top box is NTSC (analog
>>>>> only).  You won't be able to tune to it with a QAM tuner.  You would
>>>>> have to use an analog tuner set to channel 3.
>>>> But if I spit the input to the cable box then let the cable box and the
>>>> QAM card tune the same channel.  I am only using the cable box to
>>>> request the cable co to send that channel to my house.  Once it is being
>>>> broadcast I can receive it normally on the QAM card.
>>> You would have absolutely no idea where it is sending that channel to,
>>> so you would have no way to tune it with the QAM tuner.  Even if you did
>>> have a couple minutes to perform a channel scan, there would be no
>>> identifying information to denote it as such.  Even should someone write
>>> proper USB tuning adapter support for Linux, my bet is that the updated
>>> tuning data would come through an OOB event, rather than over the USB
>>> connection.
>> I'm confused here. You've just got an STB from the cableco so that you can tune
>> the channel you want. Why not just use the composite/component outputs from the
>> STB and feed them into a PVR-150/250 or HD-PVR? Why dick around trying to guess
>> which channel the cableco is going to pick to send your program on?
> That's a very good question.
> Chances are good that if these stations are indeed being broadcast 
> unencrypted, they are also being broadcast without any copy protection, 
> in which case they could be captured with a cablecard tuner.  The 
> HDHomeRun Prime has native support for tuning adapters.  On the other 
> hand, the only cable company I've heard of with significant usage of 
> tuning adapters is Time Warner, which encrypts and marks for copy 
> protection nearly everything but the local broadcast channels, which 
> will not take part in switched video anyway.
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And that is who my carrier is.  I misunderstood how SDV works. I thought
perhaps a channel was turned off while no one was using it, and then
when it was requested it was just turned on.  So I just needed to ensure
that the channel I was wanting was being watched.  Do I just need to
request a tuning adapter?  Will this work with MythTV?  I am trying to
use it with a WinTV HVR 1800.

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