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kevin at familyross

Jan 20, 2010, 2:14 PM

Post #1 of 8 (1628 views)
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Input priority

Michael T. Dean wrote:

> People generally change channel and input priorities thinking they're

> affecting which channel or which input is preferred, but they're

> actually affecting which shows are recorded.



This is at odds with the documentation. From
http://www.mythtv.org/docs/mythtv-HOWTO-12.html, in the section about Input
Priority:



"If you have multiple cards of different quality, you may want to set input
priority to encourage the scheduler to record shows on your best card(s)
whenever possible. This can also be useful if you have multiple video
sources which include the same stations. For example, with digital and
analog cable you could increase the digital cable input preference by 1 to
tell the scheduler that you want to record from the digital channel whenever
possible but the channel on the analog input could still be used when the
digital input is busy."



Is this just a case of the documentation either being wrong or misleading?
Or is my understanding wrong, you are both saying the same thing, just
different ways?



Thanks!

-- Kevin


mtdean at thirdcontact

Jan 20, 2010, 2:50 PM

Post #2 of 8 (1563 views)
Permalink
Re: Input priority [In reply to]

On 01/20/2010 05:14 PM, Kevin Ross wrote:

> Michael T. Dean wrote:
>
>> People generally change channel and input priorities thinking
>> they're affecting which channel or which input is preferred, but
>> they're actually affecting which shows are recorded.
>
> This is at odds with the documentation. From
> http://www.mythtv.org/docs/mythtv-HOWTO-12.html, in the section
> about Input Priority:
>
>
>
> "If you have multiple cards of different quality, you may want to
> set input priority to encourage the scheduler to record shows on
> your best card(s) whenever possible. This can also be useful if you
> have multiple video sources which include the same stations. For
> example, with digital and analog cable you could increase the digital
> cable input preference by 1 to tell the scheduler that you want to
> record from the digital channel whenever possible but the channel on
> the analog input could still be used when the digital input is
> busy."
>
>
>
> Is this just a case of the documentation either being wrong or
> misleading? Or is my understanding wrong, you are both saying the
> same thing, just different ways?
>

It's just a case of there being a lot more to the documentation:

The short story: it says, "you may want to," but then the rest of the
document describes the result--and should convince you that you don't
want to except in rare circumstances where you have a truly horrid input...

The longer (but still not complete) story:

-----
Order of Inputs

By default the scheduler chooses the first (lowest numbered) input which
has a showing of the scheduled program as it fills the schedule. If a
lower priority show is on at the same time as a higher priority show
that has been assigned to input 1, then input 2 will be used next and so
on. Therefore, configure your best card and input first and next best
card and input second. There may be differences in the type or brand of
capture card, signal quality from the cable, system resources such as
disk space, CPU, etc. By configuring your best input first, more
recordings, and your highest priority recordings, will use that input.

A common situation is that a newer and better card is added last. For
example, you may initially setup your system with two analog cable cards
and then add a HDTV card. If NBC is on a cable channel and "The
Apprentice" is shown in HDTV on an NBC HD channel, the scheduler would
still prefer analog inputs 1 and 2 over the new HD input 3.

So, if you'd like the scheduler to prefer a new source, the simplest
thing is to run mythtv-setup and "Delete all capture cards" then enter
your cards and inputs in your preferred order. This will not remove your
sources and channels - you want to keep those and only renumber your
cards and inputs. In this example, once the changes have been made and
the Master Backend is restarted, the scheduler would then choose "The
Apprentice" in HD on the new input 1 and only use the analog inputs (now
numbered 2 and 3) when the HDTV input was occupied with another show.
----

as well as all of section 12.6 "Scheduling with more than one Input",
including the subsection, "Input Priority," which shows the effect of
setting input priorities, and the, "Reschedule Higher Priorities,"
portion of section 12.2 "Scheduling Options," which discusses the
implications and possible consequences of that effect.

Remember that priority says how much you want to record an episode, and
there is only one priority in the end, so it's not "just" determining
where you want to record or from what channel. True, it will have an
effect on where/what channel, but it has a far greater effect on whether
or not something is recorded--especially when you realize that the
schedule you get from your listings provider is not absolute and can
change between the time the recording decision is made and when the show
you wanted to record was *supposed to* air.

Mike
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kevin at familyross

Jan 20, 2010, 3:18 PM

Post #3 of 8 (1562 views)
Permalink
Re: Input priority [In reply to]

Michael T. Dean wrote:
> [Lots of useful information]

Okay thanks for clearing that up. I guess the best way to give one input
preference over another is just make sure it has a lower ID (i.e. is added
first in mythtv-setup).

That's the way I have it now. I have 4 tuners, 2 OTA and 2 HD-PVR's for
FIOS. Of course, nearly everything that's available OTA is also available
via FIOS, but I prefer it to record from OTA when possible, then from FIOS
as a backup. My OTA tuners are first in mythtv-setup, and the HD-PVR's are
last. I've adjusted the callsigns and channel numbers to match. But I also
bumped the input priority for the OTA tuners, but I will probably now revert
that.

Thanks!
-- Kevin


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mtdean at thirdcontact

Jan 20, 2010, 3:41 PM

Post #4 of 8 (1557 views)
Permalink
Re: Input priority [In reply to]

On 01/20/2010 06:18 PM, Kevin Ross wrote:
> Okay thanks for clearing that up. I guess the best way to give one input
> preference over another is just make sure it has a lower ID (i.e. is added
> first in mythtv-setup).
>

Exactly. That way you've given preference to the input /without/
affecting recording priority for any episodes of any shows you want to
record.

It all comes down to the order you connect inputs (you can create cards
in any order), and you should use "Delete all capture cards" to reorder
things.

> That's the way I have it now. I have 4 tuners, 2 OTA and 2 HD-PVR's for
> FIOS. Of course, nearly everything that's available OTA is also available
> via FIOS, but I prefer it to record from OTA when possible, then from FIOS
> as a backup. My OTA tuners are first in mythtv-setup, and the HD-PVR's are
> last. I've adjusted the callsigns and channel numbers to match. But I also
> bumped the input priority for the OTA tuners, but I will probably now revert
> that.
>

Remember, though, it's the input order that's important, not the card
order. I.e. the backend status page shows you the card order, not the
input order.

I have 2 backends with 2 capture cards each (and /only/ local storage).
When I created capture cards, I created those on the master backend
first, then the two on the remote backend last. However, I connected
inputs on card 1, then 3, then 4, then 2. Therefore, my system's
backend status page shows Encoder 1 through 4 in order, but it will
record first using encoder 1, then 3, then 4, then 2. All my capture
cards are the same, so the reason I chose the order is to load-balance
my storage. (Encoder 1 is always used first, so the MBE does the first
recording, but since additional encoders are only used when recording
multiple simultaneous recordings, I connected 3 and 4 to pick up the
next-most-frequent usage, then 2 for the least-frequent usage.) I could
have added cards in any order (so I could add them in the same order as
I connected inputs), but I like having them organized by backend on my
status page, rather than by order of preference.

If you have set input preferences, the best way to ensure you go back to
a known state is the Delete all capture cards approach.

Mike
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g8ecj at gilks

Jan 20, 2010, 4:44 PM

Post #5 of 8 (1557 views)
Permalink
Re: Input priority [In reply to]

> On 01/20/2010 06:18 PM, Kevin Ross wrote:
>> Okay thanks for clearing that up. I guess the best way to give one
>> input
>> preference over another is just make sure it has a lower ID (i.e. is
>> added
>> first in mythtv-setup).
>>
>
> Exactly. That way you've given preference to the input /without/
> affecting recording priority for any episodes of any shows you want to
> record.
>
> It all comes down to the order you connect inputs (you can create cards
> in any order), and you should use "Delete all capture cards" to reorder
> things.
>
>> That's the way I have it now. I have 4 tuners, 2 OTA and 2 HD-PVR's for
>> FIOS. Of course, nearly everything that's available OTA is also
>> available
>> via FIOS, but I prefer it to record from OTA when possible, then from
>> FIOS
>> as a backup. My OTA tuners are first in mythtv-setup, and the HD-PVR's
>> are
>> last. I've adjusted the callsigns and channel numbers to match. But I
>> also
>> bumped the input priority for the OTA tuners, but I will probably now
>> revert
>> that.
>>
>
> Remember, though, it's the input order that's important, not the card
> order. I.e. the backend status page shows you the card order, not the
> input order.
>
> I have 2 backends with 2 capture cards each (and /only/ local storage).
> When I created capture cards, I created those on the master backend
> first, then the two on the remote backend last. However, I connected
> inputs on card 1, then 3, then 4, then 2. Therefore, my system's
> backend status page shows Encoder 1 through 4 in order, but it will
> record first using encoder 1, then 3, then 4, then 2. All my capture
> cards are the same, so the reason I chose the order is to load-balance
> my storage. (Encoder 1 is always used first, so the MBE does the first
> recording, but since additional encoders are only used when recording
> multiple simultaneous recordings, I connected 3 and 4 to pick up the
> next-most-frequent usage, then 2 for the least-frequent usage.) I could
> have added cards in any order (so I could add them in the same order as
> I connected inputs), but I like having them organized by backend on my
> status page, rather than by order of preference.
>
> If you have set input preferences, the best way to ensure you go back to
> a known state is the Delete all capture cards approach.

Does this mean what I think it does?
* no display tells you the actual order - you have to remember how you
configured it
* on your example, LiveTV always starts on card 2, that being the
'lowest' priority by order, not on the highest numbered card
* the input preference is useless, does nothing and is depreciated

I have 3 cards - a PVR150 on an STB and 2 DVB cards. The PVR150 is input 1
(is that the same as card 1?) with priority 1 and the DVB cards are inputs
2-5 and 6-9 with preference +5. Recordings for me have always used the DVB
cards first - you're saying they *SHOULD* be from the PVR150.

Very confused from NZ...

--
Robin Gilks


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mythtv at rodsbooks

Jan 20, 2010, 6:23 PM

Post #6 of 8 (1542 views)
Permalink
Re: Input priority [In reply to]

On Wednesday 20 January 2010 06:18:04 pm Kevin Ross wrote:
> Michael T. Dean wrote:
> > [Lots of useful information]
>
> Okay thanks for clearing that up. I guess the best way to give one input
> preference over another is just make sure it has a lower ID (i.e. is added
> first in mythtv-setup).

For INPUTS, yes. For CHANNELS, not necessarily. For instance, my cable company
provides digital SD and HD versions of many channels (Science Channel,
National Geographic Channel, etc.), so they come over the same input
(Firewire in my case). My cable company gives the SD channels lower numbers
than the HD channels, so the SD channels get favored by the scheduler. I
suppose it would be possible to renumber these channels in MythTV, but then
they wouldn't match the numbers used by the cable company, which could be
confusing.

I've begun dropping the priority of SD channels with exact HD counterparts
when I run into problems with SD being favored over HD. This restores HD
recordings in most cases; since the SD and HD channels carry identical
content, no recording is lost because of this change, although in my case
there can still be conflicts (I've got just one cable box, so it's
occasionally a scheduling bottleneck). If the SD and HD channels were to
deviate in content, then lost recordings would become a possibility; but
since the HD channel's priority is unchanged, the two have identical content,
and only one can be recorded at a time, the only way I can think of to lose a
recording this way is via a record-by-channel rule on the SD channel.

Going further, when the SD and HD channels are on different tuners but they
have identical content, a conflict will result in the SD channel being
recorded unless there are other shows scheduled at the same time on the SD
input. (For me, this is very unlikely; I've got three analog SD tuners, which
seldom get used any more.) If a later showing is available and there's no
conflict at that time, though, it will be rescheduled for HD recording if the
SD channel's priority is reduced. If I simply reordered the tuner cards in
the setup and left all channel priorities at 0, this situation would cause
the analog station to be recorded in SD at the earlier time. Which behavior
is preferable is of course a personal matter, and might also depend on the
shows being recorded.

Finally, I'm not too worried about conflicts causing problems I never see,
since the MythTV scheduler flags conflicts in red. (The color varies with the
theme in use.) Conflicts are therefore easy to see when I review upcoming
recordings, so spotting them is easier than spotting suboptimal recording
quality because the tuner's recording SD when an HD channel is available.

--
Rod Smith
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mtdean at thirdcontact

Jan 20, 2010, 9:02 PM

Post #7 of 8 (1539 views)
Permalink
Re: Input priority [In reply to]

On 01/20/2010 07:44 PM, Robin Gilks wrote:
>> I have 2 backends with 2 capture cards each (and /only/ local storage).
>> When I created capture cards, I created those on the master backend
>> first, then the two on the remote backend last. However, I connected
>> inputs on card 1, then 3, then 4, then 2. Therefore, my system's
>> backend status page shows Encoder 1 through 4 in order, but it will
>> record first using encoder 1, then 3, then 4, then 2. All my capture
>> cards are the same, so the reason I chose the order is to load-balance
>> my storage. (Encoder 1 is always used first, so the MBE does the first
>> recording, but since additional encoders are only used when recording
>> multiple simultaneous recordings, I connected 3 and 4 to pick up the
>> next-most-frequent usage, then 2 for the least-frequent usage.) I could
>> have added cards in any order (so I could add them in the same order as
>> I connected inputs), but I like having them organized by backend on my
>> status page, rather than by order of preference.
>>
>> If you have set input preferences, the best way to ensure you go back to
>> a known state is the Delete all capture cards approach.
>>
> Does this mean what I think it does?
> * no display tells you the actual order - you have to remember how you
> configured it
>

That's probably true. On the bright side, the best way to set things up
is to always start with "Delete all capture cards" and then re-add cards
and inputs, so you don't have to remember for very long.

And, if you happen to create capture cards in the same order as you
connect inputs, it definitely makes it easier to remember--and then the
backend status page will also show you the order. :)

> * on your example, LiveTV always starts on card 2, that being the
> 'lowest' priority by order, not on the highest numbered card
>

No, LiveTV would normally start on the lowest-numbered local card.
However, with the setting:

Avoid conflicts between live TV and scheduled shows
If enabled, live TV will choose a tuner card that is less likely to have
scheduled recordings rather than the best card available.

enabled, it does the opposite--it starts on the highest-numbered card
(and no longer prefers local cards).

Note that means LiveTV uses card order, /not/ input order (for various
not-so-interesting reasons--most of which I don't know). So, on my
setup (since I have "Avoid conflicts..." enabled), it starts on card 4,
then 3, then 2, then 1.

If I disabled "Avoid conflicts...", it would start on card 1, then 2,
then 3, then 4.

And, regardless of the setting for "Avoid conflicts..." recordings on my
system start on card 1 (input 1), card 3 (input 2), card 4 (input 3),
card 2 (input 4)--*because* all my inputs have equal priority (0, the
default, which is what 99.999% of all cards should have).

So, if I used LiveTV, the card order would be important--and, would,
therefore, affect my decision for the order to create cards.

Since people who use LiveTV probably want cards/inputs used in the exact
same order as they're used for recordings or the exact opposite order
(depending on the value of "Avoid conflicts..."), they should probably
create cards in the same order they connect inputs (in the order of the
most-preferred to least-preferred input).

However, since LiveTV uses a different criterion for order of usage, you
can actually use this to your advantage when setting things up to give
you full control over the exact order things are used for both LiveTV
and recordings. (Now that you understand the details. :)

> * the input preference is useless, does nothing and is depreciated
>
> I have 3 cards - a PVR150 on an STB and 2 DVB cards. The PVR150 is input 1
> (is that the same as card 1?) with priority 1 and the DVB cards are inputs
> 2-5 and 6-9 with preference +5. Recordings for me have always used the DVB
> cards first - you're saying they *SHOULD* be from the PVR150.
>
> Very confused from NZ...
>

No, I'm saying that making the DVB cards +4 makes any show that can be
received on them 4-higher priority than any show that can be received on
the PVR-150. So, if you have 3 shows to record and you could record all
3 using the inputs you have, but the show that would end up recording on
the PVR-150--we'll say it's LOST, your 3rd favorite show in the
world--happens to re-air later at a time when a DVB card is not busy,
Myth will probably record the #1 and #2 shows using the DVB cards and
leave the PVR-150 unused, deciding instead to record the later showing
of LOST just so it can use a DVB card. Then, at the time when the
episode of LOST was supposed to re-air, it turns out that the network
decided to broadcast something else, so that LOST episode is no longer
on the schedule, meaning you never record it.

/If/ all inputs have equal priority, they are used in input order. If
not, the priority will affect order of input usage, but--as stated
above--it also affects which shows are recorded and which airing of
shows is recorded, which affects whether shows are recorded.

Add to this channel priorities, and things get complex really quickly.
IMHO, except in very rare circumstances, no one should ever use any
priorities other than per-recording rule priorities (or custom
priorities that affect specific shows).

Or, more succinctly, input priorities are evil and channel priorities
are generally bad.

If you're using priorities for inputs or channels, you most likely want
to use negative priorities for the bad ones rather than positive
priorities for the good ones. But, don't do that unless you read and
fully understand section 12 of the HOWTO...
http://www.mythtv.org/docs/mythtv-HOWTO-12.html

Mike
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mtdean at thirdcontact

Jan 20, 2010, 9:13 PM

Post #8 of 8 (1555 views)
Permalink
Re: Input priority [In reply to]

On 01/20/2010 09:23 PM, Rod Smith wrote:
> On Wednesday 20 January 2010 06:18:04 pm Kevin Ross wrote:
>
>> Michael T. Dean wrote:
>>
>>> [Lots of useful information]
>>>
>> Okay thanks for clearing that up. I guess the best way to give one input
>> preference over another is just make sure it has a lower ID (i.e. is added
>> first in mythtv-setup).
>>
> For INPUTS, yes. For CHANNELS, not necessarily. For instance, my cable company
> provides digital SD and HD versions of many channels (Science Channel,
> National Geographic Channel, etc.), so they come over the same input
> (Firewire in my case). My cable company gives the SD channels lower numbers
> than the HD channels, so the SD channels get favored by the scheduler. I
> suppose it would be possible to renumber these channels in MythTV, but then
> they wouldn't match the numbers used by the cable company, which could be
> confusing.
>
> I've begun dropping the priority of SD channels with exact HD counterparts
> when I run into problems with SD being favored over HD. This restores HD
> recordings in most cases; since the SD and HD channels carry identical
> content, no recording is lost because of this change,

It still can be. See the last part of my response to Robin in this thread.

> although in my case
> there can still be conflicts (I've got just one cable box, so it's
> occasionally a scheduling bottleneck). If the SD and HD channels were to
> deviate in content, then lost recordings would become a possibility; but
> since the HD channel's priority is unchanged, the two have identical content,
> and only one can be recorded at a time, the only way I can think of to lose a
> recording this way is via a record-by-channel rule on the SD channel.
>
> Going further, when the SD and HD channels are on different tuners but they
> have identical content, a conflict will result in the SD channel being
> recorded unless there are other shows scheduled at the same time on the SD
> input. (For me, this is very unlikely; I've got three analog SD tuners, which
> seldom get used any more.) If a later showing is available and there's no
> conflict at that time, though, it will be rescheduled for HD recording if the
> SD channel's priority is reduced. If I simply reordered the tuner cards in
> the setup and left all channel priorities at 0, this situation would cause
> the analog station to be recorded in SD at the earlier time. Which behavior
> is preferable is of course a personal matter, and might also depend on the
> shows being recorded.
>

Exactly. But anyone messing with channel or input priorities needs to
understand what exactly they're telling MythTV--and that what they're
telling MythTV may result in missed recordings.

> Finally, I'm not too worried about conflicts causing problems I never see,
> since the MythTV scheduler flags conflicts in red. (The color varies with the
> theme in use.) Conflicts are therefore easy to see when I review upcoming
> recordings, so spotting them is easier than spotting suboptimal recording
> quality because the tuner's recording SD when an HD channel is available.
>

You need to look not just at conflicts, but also at Later showings.
Those are the problems you never see. You can have Later's even without
conflicts when differing priorities are involved. Everything looks
great today, the network changes the schedule, the later showing is
dropped, you have a missed recording an never had a conflict.

However, your use of negative priorities is the better approach if you
are using channel priorities. You have a good idea of what they do, so
as long as you're willing to live with (and not complain about--or
worse, file tickets about) the consequences, using them is fine.

Mike

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