[mythtv-users] LircChannelChanger / HD Channels - Going to wrong channel

[Gary Buhrmaster]

On Wed, Apr 2, 2014 at 6:24 AM, Jan Ceuleers <jan.ceuleers at gmail.com> wrote:
....
> YMMV, but I believe that the channeldigits parameter will not help with
> the reliability of channel changes, merely with the speed with which
> they are accepted by the STB. But I fully agree with the other guidance
> you gave (i.e. fiddling with the interdigit timers).

LircChannelChanger provides great flexibility in options.  With
such power, comes great responsibility to actually understand
how "real world" (IR) remote controls work, and which options
work in your particular use case.  Or, alternatively, steal from
someone else's experience, who has figured it out.


Tuning speeds (was digits).

There is no way for (most) STBs to know when you have
entered all the digits you are going to enter for a channel.
"Some" (typically older) devices required that you enter the
exact number of digits needed (typically 3 or 4), and
otherwise the entry is ignored.  Since that was considered
user unfriendly, most STBs these days will simply time out
after a period, and use those digits as the complete channel.

"Some" STBs will tune faster if one sends a key (often
"enter") that tells the STB that you are done tuning.  "Some"
STBs have no such key, but will know you are completed
tuning if you have entered the maximum number of digits
(so pushing '0010' on your remote was tuned as complete
for 4-digit channel tuning areas, while pushing '10' meant the
STB waited for a possible following key).

Note that this is not MythTV specific.  This is how most
(IR) remote controls work.

In any event, that "timeout" can be annoying, and delays
the tuning completion.  In particular, for MythTV, that
timeout could mean that you might miss the first 10
seconds on some recordings (if you cannot add in padding).
If the channel changer script returned to MythTV before
the tuning has completed, some capture devices reportedly
got confused (due to the capture resolution changes).

LircChannelChanger offers a couple of configuration
options to speed tuning, or minimize the impacts.  One,
as mentioned, is always send <n> digits.  Another is the
afterkey <usually enter>.  And then there is the edelay,
to simply wait before returning to MythTV (so that the
tuning is "complete" before MythTV starts the capture
device timeouts).  Which one works well for you depends
on your particular STB.


Debounce compensation compensation.

Real remotes actually send a constant stream of codes
while you are pressing the key (not just a one time code),
so that the receiving device can catch the code.  The
receiver sees that stream of (say) '0' codes, and determines
that one has pressed (and is holding) the '0' key.  With
real world (IR) remote controls, people's fingers "bounce"
a bit on the keyboard, or wave the remote around a little
(there is good human factor research to show you cannot
hold the remote absolutely steady).  So STBs that see a
stream of '0' codes, with a very small interruptions, just
presume a bouncy finger, or a waving of the hand.  They
will not acknowledge that you actually intended to stop
pressing the '0' key until some time has elapsed, *unless*
they see a different code (so, in generally, you can press
'1234' as fast as (humanly) possible, but '0001' may only be
seen as '01'.  This is often called debounce compensation,
since the key is considered to be "bouncing".  Since humans
tend to be slower than computers, and they are watching the
screen accepting the different '0's, this is rarely seen when
using the manual remotes.  But blasters are fast.  So
LircChannelChanger has a rdelay to deal with insuring that
if a '0' is sent immediately after a previous '0' (a repeated
character delay) an additional delay is added.


Conclusion

Unless someone else has a working sample for your
particular STB, one needs to experiment with the various
values in LircChannelChanger.  There is no set of values
that always work, for all STBs.  Sorry.  But, if you find
a set of values that work for you, do consider updating
the wiki with your values for the next person.