[mythtv-users] Schedule Status screen

[Jim Abernathy]

On 01/02/2018 07:43 AM, Simon Hobson wrote:
> Jim Abernathy <jfabernathy at outlook.com> wrote:
>
>> I trying to interpret what I see on the FE System Status page about
>> Schedule Status.  I have a HDHR Connect which provides 4 tuners (2
>> primary channels and 2 subchannels so I can record ATCS 5-1 and 5-2,
>> 17-1 and 17-2 at the same time).  I also have a PCIe card HDVR-2250 that
>> provides 4 tuners the same way.
>>
>> So on the Status page I see the 8 "Cards" listing how many programs will
>> be recorded on which of the 8 cards.  Since all my recordings are of
>> programs only on the primary channels, like 5-1, 17-1, why does it have
>> programs listed as recording on those cards.
> Tuners are not tied to channels. The way it works is that there is a "real" tuner that selects a multiplex by frequency, the data stream for that is then fed to a decoder that extracts one or more individual channel streams.
>
> So lets say you had a mux containing channels A, B, C, ..
> You ask Myth to record a program on channel B - it'll pick the first tuner available and ask that tuner to tune in the channel. There's an element of "hangover from the old analogue one frequency == one program channel" way of working. When the tuner is asked to tune, it'll be told the RF frequency for the multiplex (sets the tuner frontend) and the logical identifier of the digital channel (tell the decoder which digital stream you want from that mux).
>
> Now, in common with a lot of other tuners, there is the facility to take the one data stream and extract more than one digital channel from it. There aren't "multiple tuners", just the ability to extract more than one digital channel from the multiplexed stream.
> As an analogy, consider yourself standing on a bridge over a busy multi-lane road. You can choose a lane to look at (analogous to tuning a multiplex) and see a variety of traffic go past - all mixed up together. You could then (for example) focus on "small cars" and ignore the rest - that's the decoder ship extracting the data stream for a single logical channel.
> At the same time, a friend could come and stand next to you, look at the same lane (multiplex), and focus only on (for example) "large cars". And someone else could stand there looking for "SUVs". Perhaps you are involved in some sort of traffic count.
> But you are not a "small car" tuner. If your friend had been first in line then he'd have been asked to count small cars, you could have ended up counting large cars, or SUVs, or ...
>
> In the same way, when Myth wants to tune a logical channel, it will pick the first available tuner that's "suitable" and use that. The multi-rec features of Myth allow "suitable" to mean a non-existant (virtual) tuner associated with a real tuner that's already tuned to the same multiplex.
> In some cases, Myth will use two virtual tuners on the same logical channel. This is (with my settings at least) when recording two programs back-back with pre and post roll. So one program runs until (say) 9pm but recording will not stop until 9:10 due to post roll, the next is due to start at 9 but recording starts at 8:55 due to pre-roll - 15 minutes overlap.
> The first program will be scheduled to record on the first tuner (Card1), the second program will be scheduled to record on the second virtual tuner (Card2) - so as to not tie up another physical tuner when it's not required.
>
>
>> 33 on Card1 HDHR1
>>
>> 9   on Card2 HDHR1
>>
>> 10 on Card3 HDHR2
>>
>> 4   on Card4 HDHR2
> This looks like a normal distribution. The most recordings (33) happen on the first tuner. Then there are another 9 recordings which overlap with an existing recording on the same multiplex being used by Card1 at the time.
> Then there are 10 recordings which need a different multiplex to that being used by Card1, and 4 that overlap with those recordings and share a multiplex.
>

Thanks for the very good explanation.  I was confused because I thought 
Card 2 and 4 could only record the SD stuff on the sub-channel and Card 
1 and 3 would only record the primary sub-channel. I do have a lot of 
back to back recordings that would overlap due to pre and post roll.

Again, Thanks a lot.

Jim A

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