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

Raymond Wagner raymond at wagnerrp.com
Mon Oct 31 16:29:08 UTC 2011

On 10/31/2011 11:41, Colin Albert wrote:
>> On the otherhand, the only cable company I've heard of with
>> significant usage oftuning adapters is Time Warner, which
>> encrypts and marks for copyprotection nearly everything but
>> the local broadcast channels, whichwill not take part in
>> switched video anyway.
> 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.

As mentioned, it's not that the physical channel is switched off until 
it is needed, for some power saving measure.  Rather the digital stream 
is not being sent until it is needed, at which point a physical channel 
and stream identifier are randomly allocated, according to where ever 
there is free bandwidth to take it.  There is no way for MythTV to know 
where this channel will end up, and it is very likely to be encrypted 
where ever it does end up.

You can use a cablecard tuner, as those will receive the necessary 
updates to know where the new channel is.  MythTV (or Linux for that 
matter) doesn't have tuning adapter support, but the HDHomeRun Prime has 
a USB port to support everything internally.  However, Time Warner likes 
to encrypt everything, which will almost certainly include the switched 
channels, meaning cablecard tuners will not allow MythTV or any other 
unauthorized application to record those channels.

That leaves all the old methods.  Firewire capture from a cable box is 
going to have the same copy protection limitations a cablecard, so that 
option is out.  That leaves analog capture, either high definition 
component from an HDPVR, or standard definition S-Video from an MPEG 
encoder card.  While your HVR-1800 is an MPEG encoder, and even one with 
Linux drivers, as last I've heard, there are some issues with that 
driver that prevent it from behaving properly when used with MythTV.  
The HVR-2250 and HVR-1600 do work fine with MythTV, as do the older 
PVR-150s and PVR-500s that can still be found used on ebay.  You will 
need IR, or possibly firewire, to allow the backend to change channels 
on the cable box.

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