[mythtv-users] Comcast OnDemand on Multiple STBs

Paul Onley onley at worldnet.att.net
Fri Nov 9 07:33:06 UTC 2007

> By my understanding, the "extra information" you're trying to get from 
> the backend is which capture card is being used to record the show so 
> that you can use it to submit the commands to the STB using the proper 
> "remote codes."
> If this is the case, you have 2 (easy) options:
> a) Create 4 scripts, change_channel_stb1, change_channel_stb2, 
> change_channel_stb3, change_channel_stb4. Then, map the appropriate 
> script to the "External channel change command" for the input connected 
> to that STB. Since the "External channel change command" is a per-input 
> setting, you use each of the 4 scripts for your 4 inputs.
> b) Create 1 script which accepts 2 arguments: the STB identifier and a 
> channel number. Then, for the "External channel change command" foreach  
> input, use "change_channel 1", "change_channel 2", ... The channelnumber  
> will be appended to the command after the command and argumentyou  
> specify. So, you use the STB ID (1, 2, 3, 4) to determine whichremote  
> code to use and use the channel number to send the appropriatecodes to  
> the STB.
> So, the idea isn't to get Myth to send additional data to the channel 
> change script, but to call the "right" script (for a, or call the script 
> correctly, for b). I used both approaches as various times to controlmy  
> 2 STB's. Granted, I haven't used firewire output, before, but sinceyou  
> mention Myth is sending channel information to an "external tuner 
> script," I'm assuming it works exactly the same way for firewire as it 
> does for analog capture cards.

> HTH. And, thanks for bringing the discussion to the -users list.
> Mike

Hi Mike, Thanks for the reply but over the course of several replys
my original intent became blured.

>> I am trying to create a setup where I can control multiple STBs and 
>> navigate the Comcast OnDemand menus. I have the channel changing scripts 
>> working using the serial ports but I can't find any way to send anything 
>> other than the channel info to the STB. I need to send left, right, up, 
>> down and select to the STB but since there are 4 STBs this info will  
>> haveto be sent through the backend to get to the right box.
>> Mythtv breaks out the tuning info and sends it to the external tuner 
>> script but I don't see any way to send other info to the external tuner 
>> script. Is there a hook that I don't know about or is this something  
>> thatcould be implemented?

I need to send non-channel info to the STBs to use the On Demand
programing feature (this is channel 1 on Comcast and once there you
interact with onscreen menus to select a show to watch. Many feel this
service has no value with a Myth system but it has great content for
the kids) on Comcast cable. I have the 4 STBs working and have
added code to DCT2000 channel_change script so that it will accept
a command line arg for the serial port. I then give the serial arg in
the "external tuner command" area in myth so that all 4 STBs can use
the same script. This is all working very well. My problem is that I
need to be able to send other codes to the STBs to interact with on
screen menus that are not part of myth. I would like to be able to send
these through the SAME mechanism that we have outlined here so that I
don't have to interogate the backend to see which tuner I am watching
and then send the left, right, up, down, and select codes to a daemon
on the backend which will then pass them to the appropriate STB.

My first approach was to choose dummy channels and setup the lircrc
config file to send say 981 when you press the down arrow. Then I went
into the channel_change script and setup a case that would change 981
to DOWN and send it to the STB. This worked like a charm but Myth will
not send a channel change to the STB if you are already on that channel
so you could never send 2 consective down arrows for example. I posed
this in DEV as I thought it would be possible to preface a command
(esc code it if you will) so that myth would send it to the built in
"external tuner command" but digging into the Myth code is above my
ability. The best approach I have yet been able to come up with is to
have lircrc call a script when the down arrow is pressed that will
interogate the backend to see which STB I am watching then send the
STBs ID and the desired code to a daemon on the backend which would
forward the code to the correct STB. This is a lot more monkey motion
than being able to ask Myth to do it through the channel change mechanism.


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