How does WMC work when Comcast adds new channels

[benhase]

Gary,
I am trying to understand how WMC works when Comcast adds new channels.
My configuration is WMC on Windows 8.1 with HDHRprime and Comcast.

I run the HDHRprime "Detect Channels" (via http://192.168.1.x/lineup.html) which shows 325 channels.
I remove the duplicates (channels over 1000) and the non-HD channels leaving 91 channels when I create my guide (mxf.xml).
I load the guide via: C:\Windows\ehome\loadmxf -i mxf.xml.
I then run epg123Client.exe and click "Match by: # Number".
At this point I can use WMC to watch TV and view the guide for the 91 channels (great).

When Comcast adds a new channel, I just assure it is in the guide, load the new guide, and re-run "Match by: # Number".
I can then view the guide and watch the new channels with WMC (no need to redo HDHRprime "Detect Channels").

I also use NextPVR (with the same HDHRprime) on Windows 10.
As you know, the guide for NextPVR (xmltv.xml) is a different format than "mxf.xml" for WMC.
NextPVR has web page menus: "Guide", "Devices", and "Channels" to load and map the guide to channels.
However with NextPVR, the new channels do not show up until I redo the HDHRprime "Detect Channels".

My Question: How does WMC find the new channels added by Comcast without me re-running the HDHRprime "Detect Channels"?

[garyan2]

WMC doesn't use the stored channels on the HDHRs, or it's discoveries. WMC talks directly with the tuner to tune channels using the BDA driver whether there is actually something there to tune to or not. If you ran WMC TV Setup and denied the Program Guide Terms of Service, you will have 9999 channels available to tune to, so there are no channels "added". It is just your provider may add a new stream that is assigned to a channel number that WMC already has in its' database.

I get the feeling that those with Tuning Adapters are a little different than what I said above, but I've never seen that setup so can't make much of an educated guess.

[benhase]

Thank you, Gary for answering my question. This is the first I've heard of Broadcast Driver Architecture (BDA). I'll do a little research on BDA.

Using WMC I went to Tasks - Settings - TV - Guide - Edit Channels, I see the 9999 channels (yes, I denied the Program Guide Terms of Service) and selected a few channels not in my guide. As expected (by your answer), WMC either displayed the TV signal (and "No data available"), or after a bit of a delay "Service is unavailable" There is currently no TV signal...

[Space]

As far as I know, with a tuning adapter, it is the same (at least as far as WMC is concerned).

I don't know the details, but at a high level...

The CableCard Device periodically downloads a channel map from the service provider. This channel map is a listing of channel numbers and what frequency to tune to to receive that channel (among other things).

When using a tuning adapter, the map just tells the device that when you try to tune to the given channel, to request the channel through the tuning adapter, then the adapter tells it what frequency to tune to (assuming the TA was able to successfully assign the frequency for that channel in your area). When it is successful, it streams the channel back, just like a regular channel, or it gives an error if it was unable to successfully allocate a frequency for the channel.