[mythtv-users] Request info to setup virtual tuner

[Stephen Worthington]

On Sun, 23 Jan 2022 09:18:00 -0500, you wrote:

>
>
>> On Jan 23, 2022, at 8:44 AM, Phil Nash <philnash800 at gmail.com> wrote:
>> 
>> Hello,
>> 
>> I was reading a post of yours from August in a mythtv mailing list.  I have two HDHR dual-tuner boxes like you mentioned but one of mine is a slightly older HDHR3-US.  Therefore in mythtv I've configured 4 physical tuners.  You mention going back afterwards and adding more multirec virtual tuners.  I am assuming that only my newer HDHR4-US is capable of this but maybe they both are.
>> 
>
>Your HDHR3 tuners are able to do virtual tuners as well as the new HDHR4.
>
>When you go into mythtv-setup, the additional virtual tuners are defined in the following menu tree:
>
>Input connections. You will need to step thru each of the 4 connections you would have for your defined tuners. 
>  Select them one at a time.
>    Interactions between inputs at the bottom of the list of choices.
>      Max Recordings, I have mine currently set to 4. You can set however many you want.  This effectively gives 16 virtual tuners total for the 4 hdhr real tuners.  We do have real channels in our area that have up to 8 virtual channels and on channel that has 1 1080i, 2 720p, and 2 480i virtual channels.
>
>I seem to recall that there is a limit of 5 virtual channels that can be recorded by mythtv tho.
>> If you can answer a couple questions I'd appreciate it greatly.
>> 
>> What tuner card "type" do I choose when I'm adding the multirec tuner?  HD Homerun again? 
>Doesn’t matter, you aren’t adding additional homeruns
>> Once they're all defined do changes to scheduling priorities then need to be made?  Which changes?
>Nothing I know of.
>> I think the multirec tuners only benefit someone who would be tuning two channels at the same time that happen to be both included on the same multiplex.  Am I correct in this thinking?
>> 
>> 
>Doesn’t matter, all the virtual tuners are constricted by the 20( or so ) mbps that can be ’streamed over the air on ATSC 1.0 . The HDHR tuners are just dumping that data when asked as far as I understand.
>
>There are others in the mailing list that can give better details if wanted.
>
>I replied to the mailing list as this is good information for the list.

Multirec tuners allow mythbackend to record multiple channels from the
same multiplex at the same time using the same physical tuner.  The
tuner needs to be of a type that supports this (such as DVB-T, DVB-S,
ATSC, ...).  When mythbackend records a programme from one of these
tuners, it sets up the tuner so it can record all the streams for one
channel to a disk file.  When it does multirec recordings, it sets up
the tuner to send all the streams for all the channels it wants, and
sends the streams for each channel to different recording file, one
per channel.  Tuners can have the capability of filtering out the
streams specified in the tuning command and only sending those streams
to the CPU.  If the tuner does not have that capability, it will send
the complete data that it is receiving for a multiplex (all the
streams) to the CPU and the tuner's driver will filter out the
requested channels only and send them to mythbackend.

Most other tuners that do not support multirec as such do allow you to
set the max recordings setting to 2 to allow two recordings at once
from the same tuner.  This allows you to overlap the pre- and
post-roll for back to back recordings using the same tuner.  IPTV
tuners work like this, so you can record back to back programmes using
just one IPTV stream instead of needing to use two streams during the
overlap period.