[mythtv-users] Live TV playback frustration

[Michael T. Dean]

On 08/24/2012 01:27 PM, Ian Wilkinson wrote:
> On 24/08/2012 16:39, Michael T. Dean wrote:
>> On 08/24/2012 09:03 AM, Ian Wilkinson wrote:
>>> On 24/08/2012 11:50, Michael T. Dean wrote:
>>>> On 08/23/2012 03:15 PM, Ian Wilkinson wrote:
>>>>> You could setup a recording and watch it live from the recordings
>>>>> list (as is the recommended method in Myth).  However, if you were
>>>>> channel surfing and stumbled across it (perhaps you'd forgotten it
>>>>> was on but fancied watching it there and then), you could wind back
>>>>> to the start of the show without going to the recordings list.  It
>>>>> just used the recording file when you reached this channel when
>>>>> surfing.
>>>>>
>>>>> Does myth do this? No, it insists on creating two recordings of the
>>>>> same thing, because myth is not looking at providing the user with
>>>>> the content, myth is just looking at it as two different consumers
>>>>> that both happen to be receiving the same data.
>>>> In MythTV, Live TV has an implied contract that the Live TV viewer is
>>>> the "owner" of the tuner.  If you were channel surfing and stumbled
>>>> across a channel on which a scheduled recording is occurring and
>>>> MythTV noticed and instead started playing back the scheduled
>>>> recording, it would presumably "release" the tuner you were using for
>>>> Live TV.  And, unlucky you, your wife just happened to start Live
>>>> TV--and claim that just-released tuner--right before you hit channel
>>>> up, again.  Now you've lost your tuner, so what to do?
>>> Ok so in a two physical tuner system, when two recordings are taking
>>> place on two different mux, in LiveTV I'm limited to the channels on
>>> those two mux.  Same deal here, I'm limited to the channels that are now
>>> available.
>> No, that's different--you didn't lose your tuner, it only got locked
>> to a mux, but you can still switch to any channel on that mux (or any
>> other currently-in-use mux).  Being locked to a mux is the result of
>> using a "software hack" to pretend you have more tuners than you do.
>> A physical tuner may be locked to a mux and prevent a Live TV user
>> who's using one of its virtual tuners from changing channel (with that
>> tuner) to one on a different mux.  However, the Live TV user stuck on
>> that mux can still change channel between any of the channels on that
>> mux without switching physical tuners.  (But in 0.25+, MythTV will
>> actually switch to another virtual tuner on a different physical
>> tuner, which may be locked to some other mux.)
> Right, ok sorry again I didn't make myself clear.  I was suggesting that
> if Myth did as you had suggested and swapped onto the tuner that was
> recording the programme, when you tried to change channels afterwards
> that it wasn't any different to the current situation on a dual tuner
> system when both tuners are already in use and you try to start Live TV.
>
> I will concede that if you have a dual tuner system and only allow one
> recording per physical tuner (why would you want to do this?)

This is not what I'm saying.  What I'm saying is MythTV Live TV /only/ 
switches tuners when it is forced to (because the user requested a 
channel on a Video Source or mux that isn't available on the current 
tuner).  Virtual tuners (or lack thereof) have nothing to do with it.

Therefore, if MythTV switches tuners in Live TV, it's because you were 
already restricted in what you could watch--you had already lost some 
control of the tuner before it switched.  So at this point, there's no 
loss of control due to switching.  You imply that the situation I 
described--based on your "give up the tuner and watch the 
already-recorded episode" approach--is the same as could happen with 
current MythTV, but since with current MythTV, you only switch tuners if 
you already have a "limited" tuner, you're not losing any control.  If 
you completely release a tuner because there's already a recording of 
that episode, you are--which is a huge problem if I'm just channel 
surfing through a channel that I didn't know was recording a show and I 
lose the ability to watch Live TV (which I started before little Johnny 
started his Live TV, so I should get priority) because of my 
unfortunately-timed channel change.

>   that you
> do have a slightly different situation.  However, I still don't see
> what's wrong with subsequently being restricted to only viewing channels
> on the 2 mux.  If no tuners are free myth when selecting Watch TV, it
> should either drop you into one of the recordings and allow you to surf
> to the other, or just give you the two choices, rather than telling you
> that no tuners are free.
>
> As most of your response seems to be from the point of view of what Myth
> does do, rather than what it could do if we swapped to the other tuner,
> I've snipped it...
>
> <snip>
>>>> What you describe is easy to implement in a single-system setup.
>>>> MythTV is a multi-system DVR that may have more than just one
>>>> concurrent user on any of potentially many frontend systems.  We need
>>>> a way to ensure that Live TV continues to work like Live TV even if
>>>> you surf through channels with scheduled recordings.
>>> Hopefully from my examples above, I've demonstrated that it is not a
>>> multi-user problem,
>> I completely agree.  In your examples, the problem is using virtual
>> tuners and assuming they are a valid replacement for a physical
>> tuner.  :)  That said, your examples don't play out quite like you
>> thought because we only switch tuners in 0.25+ if we have to because
>> the tuner in use is already locked.  Once this is understood, you'll
>> see that we try our best to maintain the contract that a Live TV user
>> owns the tuner--and it's only when a Live TV user is using a virtual
>> tuner on a physical tuner that's locked to a mux (an "already hobbled"
>> tuner) that Live TV switches tuners.  (Or, technically, we'd also
>> switch tuners if you requested a channel on a different Video Source
>> that's unavailable on the current tuner.)
> Why do the tuners have to be allocated at all to a user?
> Why can't myth simply treat the tuners as mux sources, and assuming
> enough available backend capacity, allow a user to watch any channel in
> those available mux?

Because, by definition, MythTV can not know what a user is going to do 
in Live TV (what he will watch or what channels she will change to and 
when).  You can't plan for the unexpected.  Therefore since the user 
expects to be able to control Live TV, we have to do our best to make 
sure they have--and maintain--such control.  Note, also, that the entire 
problem becomes significantly more complex if you stop looking only at 
"now" and try to plan for later, too.

Look back at all the, "Well, if I'm just watching through my TV without 
MythTV, I never ..." threads in the archives to see how much control 
users expect of Live TV.

Again, notifying the user and letting them /choose/ to exit Live TV and 
watch the in-progress/previously-recorded version of the episode would 
be a good thing.  But it needs to be a conscious decision the user makes 
and not some "I'll just force you out of Live TV" approach.  And, FWIW, 
reserving a tuner but not using it is a waste.  And, yes, with that 
statement, I'm *also* implying that Live TV itself is, by definition, a 
waste (because it reserves a tuner and potentially records something 
that's already being recorded)...  :)  There's no way to make Live TV 
not be a waste because the implied contract of control involves wasting 
resources on Live TV.  (Thus my--possibly over-the-top--distaste for 
Live TV.)

> Or more importantly, why should a user /Care/ about tuners?  When they
> hit Watch TV, it should just work and let them view either of the
> currently recording programmes, or something else from those mux.  There
> shouldn't really be a need to tell the user that a tuner isn't available.

That's exactly how it works now (in 0.25+), with the exception of 
informing them of/letting them easily switch to recorded episodes.  
(Note that you /can/ switch to recorded episodes through the OSD Menu, 
but with current MythTV you would have to know to do that.)

Users are never told that tuners aren't available.  They're only told if 
a channel they're trying to tune isn't available (and only if it's not 
possible to tune it anywhere).

> I'd agree that the virtual tuners are a hack to provide additional
> recording ability, but in reality it should be enough to setup the
> physical tuners then myth should just test to see what the realistic
> bandwidth limit is from a tuner and also what the maximum simultaneous
> bandwidth is from all tuners and allow myth to create any virtual
> devices to fix problem of having to allocate a tuner to a recording
> before it takes place.

Yes, and this is something we would like to do eventually, but someone 
has to code it.  However, it would really only save a tiny bit of 
configuration (changing the default of 2 tuners for multirec-capable 
devices by hitting up/down on the combobox) and wouldn't really affect 
what the user can do, assuming the user configures a reasonable number 
of virtual tuners for their system.

> I have two physical tuners setup as 4 virtual tuners, but I've no idea
> what my hardware could cope with as I don't want to be responsible when
> the recordings start to fail.
>
> I just figured as the old commercial box used to let us have three
> simultaneous streams (two recording to disk and one to watch) from two
> tuners so the new one should be able to do at least one better than that.
>
>>>>> Don't get me started with the problem with two recordings on the same
>>>>> mux using both tuners and stopping LiveTV from receiving any other
>>>>> mux, or the fact that you have to /Manually/ change input to use an
>>>>> inactive tuner, or to see channels on the other mux if two recordings
>>>>> are in progress.  My wife asks almost every week why it won't let her
>>>>> see something on ITV2 when she knows it's recording ITV1 and BBC1,
>>>>> the Topfield just worked and sorted it out and she knew she couldn't
>>>>> get to channel 5, etc, but was happy with the experience.
>>>> 0.25-fixes and above should automatically switch tuners when another
>>>> tuner is available.  It sounds like you're still on 0.24-fixes or
>>>> below.
>>> Yes, I'm still on 0.24-fixes, I've looked at upgrading to 0.25 several
>>> times, but the number of issues that people seem to still be
>>> experiencing has put me off.  I just don't need the grief at the moment.
>>>
>>> Does this change in 0.25, now resolve the issues around having freeview
>>> and freesat where some of the channels are available on both platforms,
>>> but both also exclusive channels?  Previously couldn't just surf from
>>> "Dave" on Freeview to "CBS Action" on freesat without going into the
>>> menu and manually changing source.
>>
>> Yes, MythTV 0.25+ Live TV will allow switching to any available
>> channels.  If the channel requested is only available on another
>> physical tuner (whether it's due to different Video Sources--i.e. the
>> channel is only available from DVB-S but the user is currently
>> watching DVB-T--or due to the Live TV physical tuner being locked on a
>> mux and the requested channel is on another mux), MythTV will switch
>> tuners.  (Note, also, that this was the way it was always supposed to
>> work, but a couple of devs actually went to the trouble of fixing the
>> bugs that prevented it.)
>>
> A big Thank You to the (unnamed) Devs!  When I do upgrade I will finally
> be able to add the freeview channels into the freesat setup I've got at
> the moment without having to take my wife through the additional steps
> of changing tuners.
>
> Hum, so in a dual tuner system, one DVB-S and one DVB-T system, with no
> virtual tuners.  With no recordings taking place, I can start Live TV
> and I can surf from DVB-S to DVB-T and myth will go from one tuner to
> the other, if my wife then starts Live TV as well is she then limited to
> DVB-S and I become limited to DVB-T?

No, in 0.25+, MythTV will allow you to change to any channel on any mux 
or any Video Source that's available, regardless of which 
card/device/input makes it available and whether it's available due to 
someone else's watching Live TV or some recording in progress or some 
different-but-available-and-not-in-use physical tuner.  If you ask for a 
channel change, it just happens, regardless of how/where it gets 
tuned--with the exception that if /all/ of your physical tuners are 
locked to muxes and you request a channel change to a channel on a mux 
that isn't tuned by any physical tuners, you will get a message saying 
that channel isn't available.

Mike

P.S. I'm leaving the devs unnamed, for now, because I don't want to miss 
any of the ones who worked on it.  I'll just say that *I* had no part in 
fixing it.  :)