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Multiple Front ends, one Backend
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Author:  mschlott [ Sun Jan 29, 2006 8:49 am ]
Post subject:  Multiple Front ends, one Backend
I'm new to myth, but have read the install guide and searched the forum. I would think this would be a faq, but I have not come accross it.

This is my understanding of myth.

A single box can operate as either a backend, a frontend, or both.

The backend runs a mysql database which stores metadata.

Not sure about this, both the backend and the front end have tuners and can store movies localy.

The front end does not need to have a tuner to play movies stored on the back end.

Is it possible to have a front end set top box with no tuners, and a backend box with tuners, and watch live TV on the front end? If so, could you have a super backend box with 4 tuners and 3 front ends with no tuners and watch live TV on all 3 while recording a 4th? If so how would you go about assigning a tuner on the backend to a front end to ensure each front end would always be able to controll at least one tuner.

I suspect that it is not possible for a tunerless frontend to watch live tv.

If there is an architecture overview or an idiots 50,000 ft overview of how mythtv works, please point me to it. I'm willing to read.

Thanks in advance.
mike
Author:  Xsecrets [ Sun Jan 29, 2006 10:53 am ]
Post subject: 
Not exactly. If a box has a tuner it is a backend period. You can have master and slave backends. A frontend only box has no tuners, but can still watch livetv/recordings off of a backend.
Author:  tjc [ Sun Jan 29, 2006 10:56 am ]
Post subject:  Re: Multiple Front ends, one Backend
mschlott wrote:
The backend runs a mysql database which stores metadata.

The backend stores the recordings too.
mschlott wrote:
Not sure about this, both the backend and the front end have tuners and can store movies localy.

No. If it has tuners it's a backend. This has to do with the way that the software's work is divided. The mythbackend server is all about dealing with hardware like tuners and storage. It's basically just a big data management engine. The frontend deals with user interaction and generally gets it's data services from the backend.
mschlott wrote:
Is it possible to have a front end set top box with no tuners, and a backend box with tuners, and watch live TV on the front end? If so, could you have a super backend box with 4 tuners and 3 front ends with no tuners and watch live TV on all 3 while recording a 4th? If so how would you go about assigning a tuner on the backend to a front end to ensure each front end would always be able to controll at least one tuner.

The mythfrontend behaviour is essentially uniform whether it shares the machine with the backend or accesses it remotely via the LAN. Systems with multiple tuners are quite common, I've got two, lots of folks have three, and 4 or more is not unheard of using something like the PVR-500. Even with multiple tuners there is no certainty that even one will be free if there are enough recordings that the box is trying to do at the same time, but it does significantly increase the chances.

OBTW - It's a common misconception to think that the backend is a big high powered machine and the front ends can be low powered. This isn't the case. Given a PVR card, what backends need is a lot of storage, not a lot of CPU. Frontends need a far amount of CPU power to decode and display the image smoothly, but don't need much storage of their own.
Author:  mschlott [ Sun Jan 29, 2006 1:06 pm ]
Post subject: 
If I have a backend with 2 tuners, and 2 frontends, both frontends could be watching the same live programe from one tuner, while a second show is recorded on the second tuner. What happens when one person changes the channel on one of the front ends?

I'm guessing that each front end selects a video input, and views whatever is coming from that input. If one of the front ends requests a channel change on that input, whoever is viewing live video from that input sees, the change.

This sounds like a nice big brother tool to see what someone else is watching. :)

As was suggested to me in the HDTV forum, I think I'll buy a 150 or 500 and play for a while. I'd just like to understand as much as possible before I start.


mike
Author:  Xsecrets [ Sun Jan 29, 2006 1:34 pm ]
Post subject: 
no two frontends cannot view from the same tuner. once a frontend grabs a tuner that tuner is locked and the next frontend gets the second tuner or a message that no tuners are available if you are out. So two frontends watching "livetv" even if it's the same thing would use up both tuners and there would not be one available to record anything. however if you have a recording, or even if a show is currently recording multiple frontends should be able to view that recording simultaneously without using any tuners or just one tuner in the case that the show is currently recording.
Author:  nermander [ Mon Jan 30, 2006 2:02 am ]
Post subject: 
Xsecrets wrote:
no two frontends cannot view from the same tuner. once a frontend grabs a tuner that tuner is locked and the next frontend gets the second tuner or a message that no tuners are available if you are out.


But isn't that supposed to "go away" in 0.19? When all live TV really becomes recordings?
Author:  Xsecrets [ Mon Jan 30, 2006 8:50 am ]
Post subject: 
well yes/no if you browse to the hidden livetv recordings folder and view the recording then multiple people will be able to view it, however if you choose the watch tv option from the menu you will grab a tuner and it will start a recording for you. and if someone else does it will start another recording of the same show, at least that's the way I understand it. I doubt they have built any more intelligence than that in yet.
Author:  tjc [ Mon Jan 30, 2006 7:37 pm ]
Post subject: 
As far as I can tell from my experiments that's exactly what it does. It does seem to have some interesting intelligence related to channel surfing, where "live" recordings below a certain length apparently vanish almost instantly.
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