[mythtv-users] interfacing MythTV with a DTA, lirc queries

Gary Buhrmaster gary.buhrmaster at gmail.com
Mon Jul 25 17:16:21 UTC 2016


On Mon, Jul 25, 2016 at 3:01 PM, Timothy Krantz
<tkrantz at stahurabrenner.com> wrote:

> I will be curious to see how he makes out.  My cable provider uses up to 4
> digit channel numbers and I could never reliably get the channel change
> script to work.

Some advanced channel changer scripts have some
ability to "adjust" for various artifacts that some IR
receivers have regarding de-bounce and repeated
character protection(*).  However, tuning those
values for your particular IR receiver is known to
require some trial and error (often lots of error),
because with extremely rare exception their is zero
documentation on what those values actually need
to be set at.  When I used such external channel
changing scripts I spent a fair amount of time finding
what values of delays were (highly) reliable.  There is
no shortcut unless someone has done the work for
you for your particular device (bonus points: firmware
updates can change the required delays/values!)

Also note that if one has multiple devices that need
to change the channel at the same time one must
use scripts with appropriate locking since irsend sets
some global values that (if there is no locking) can be
reset by other channel changing scripts which leads
to some confusion.




(*) All real world IR receivers build in some protection
against someone who hits a key, and then the finger
moves a bit, and the key is released, and is pressed
again.  You do not want to see a '1 1 1 1' because
your finger moved a bit.  So there needs to be a
minimal time between the release of the key, and it
being pressed again to be seen as multiple '1's.
That delay can often be reduced when difference keys
are pressed (so you can press '1 2 3 4' faster than
you can press '1 1 1 2'), so you only need to add
such delays for repeated keys.


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