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

Raymond Wagner raymond at wagnerrp.com
Sun Oct 30 17:12:10 UTC 2011

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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