Mailing List Archive

What do you mean by a "mythbackend box"?

Any box with a tuner card that you want to use with Myth needs to run
mythbackend, and needs to save the data to its own disk. A network file
system (NFS, Samba, etc) will not provide enough throughput (regardless of
how fast your network is). In your case, you probably will want to set up
one box w/tuner as the master backend and the other 3 as slave backends.
Myth will take care of integrating the files on the different boxes into a
single 'view' for the frontend. Any, all or none of your backends can also
be frontends at the same time, as long as the box is fast enough to handle
simultaneous encoding (record) and decoding (playback/LiveTV). My advice is
choose your best tuner card & put it in a powerful box with the biggest disk
you have. Set that box as the master backend, then configure the other
boxes as slave backends.

Another option is to put multiple tuner cards in a single backend. This
ability is only limited by the ability of your box to record/encode multiple
programs simultaneously, and the availability of sound inputs on that box.

As far as the hardware goes, the backend does not need a video card. A
sound card will be necessary for each tuner that doesn't support btaudio,
but you only need line-in (record) capability for a standalone backend.

Hope that helps.

-Joe C.

> -----Original Message-----
> From: mythtv-users-bounces@snowman.net
> [mailto:mythtv-users-bounces@snowman.net]On Behalf Of RJV
> Sent: Sunday, March 30, 2003 11:23 PM
> To: mythtv-users@snowman.net
> Subject: [mythtv-users] Question about Mythbackend
>
>
> Is it possible to run mythbackend on a server box that has neither a video
> card nor audio card?
>
> I've got a serverbox that has oodles of space that I'd like to press into
> service as a mythbackend box, but I couldn't find any info about this
> particular setup on the main page.
>
> I've got 4 other boxes with tv cards that I'd like to have connect to a
> server box and save the data there.
>
> -- RJV -- ..ooOO miracle@procyon.com
>
> -- Institution of Postgraduate Education - Graduation 2001
> -- Institution of Undergraduate Education - Alumnus 1997
>
> The opinions expressed in any email originating from this account are the
> sole opinions of the author. They do not reflect the opinions or policies
> of any institution or individuals other than myself.
>
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Joseph A. Caputo wrote:
> What do you mean by a "mythbackend box"?
>
> Any box with a tuner card that you want to use with Myth needs to run
> mythbackend, and needs to save the data to its own disk. A network file
> system (NFS, Samba, etc) will not provide enough throughput (regardless of
> how fast your network is).

I agree with most of this very helpful response but this isn't
exactly true. Writing to a local disk is certainly preferable
but if the recordings are, say, 1.5GB per hour that is still
less than 1/2 MB per second. This won't work over a wireless
network, questionable for a 10Mb network and won't work for
more than one recording at a time. However, a 100Mb net would
work and, in fact, there are people out there using NFS. The
problems with multiple NFS recordings would likely be latency
rather than throughput. With four recordings over NFS that's
still less than 2MB/sec but with four connections competing
to deliver packets to the server and the disk heads thrashing
to write four files, the encoders would probably be dropping
frames as they couldn't write their data in time.


> In your case, you probably will want to set up
> one box w/tuner as the master backend and the other 3 as slave backends.
> Myth will take care of integrating the files on the different boxes into a
> single 'view' for the frontend. Any, all or none of your backends can also
> be frontends at the same time, as long as the box is fast enough to handle
> simultaneous encoding (record) and decoding (playback/LiveTV). My advice is
> choose your best tuner card & put it in a powerful box with the biggest disk
> you have. Set that box as the master backend, then configure the other
> boxes as slave backends.

Good explanation. I agree. Currently, the tuners are assigned
in order so 1 is always first. 2 is only used when 1 is busy
(live TV or recording) etc. Therefore the master should have
the biggest disk (and the best tuner ;-).

> Another option is to put multiple tuner cards in a single backend. This
> ability is only limited by the ability of your box to record/encode multiple
> programs simultaneously, and the availability of sound inputs on that box.

Right but you may not want to use more than two tuners in a
singles server.

It used to be that the scheduler knew how to use one or two
tuners. With the multi-backend, it can now use any number of
tuners no matter where they are. Therefore, leading up to the
0.8 release I tested three tuners on one machine and it 'worked'.
I know that four would 'work' but this is kind of a pointless
exercise.

To do medium to good quality recordings with mpeg4 you need
about 1GHz per tuner. The parameters have to be set low enough
so that it will work when all tuners are busy. This means that
if you got a bleeding edge >3Ghz CPU and several tuners, it
could only give you medium to low res recordings and not make
use of it's resources the vast majority of the time.

You may want to consider two dual servers for your four tuner
cards. Local disks on each of the servers then lightweight,
diskless systems for your four frontends.

Again, the first card is always used first so the master
needs more disk space. However, if you modify the database
so that the card order is master=1&4, slave=2&3 the disk
usage should be more evenly distributed.


Back to the original question ;-), I haven't tried it but
a backend should be able to work without a graphics card.
However, as Chris Palmer pointed out earlier, the backend
"setup" program needs X so you would have to install the
X packages and remote X authentication just to go through
the setup program. After it is installed, it should no
longer need X (at least until the next time you go to change
something in setup).

No audio card can only work if btaudio works for your cards.
AFAIK, there is not make/model that is sure to always work
much less work and have good sound quality.

-- bjm

On Monday, March 31, 2003, at 04:10 PM, Bruce Markey wrote:
> No audio card can only work if btaudio works for your cards.
> AFAIK, there is not make/model that is sure to always work
> much less work and have good sound quality.

From what I've read, the WinTV model 401 works for everyone. It
certainly works for me, and is indistinguishable (to my
not-highly-attuned-ears) to the quality via the sound-in on a
soundcard. The only issue is the irritating short burst of static when
you change channels.

James

James Knight wrote:
> On Monday, March 31, 2003, at 04:10 PM, Bruce Markey wrote:
>
>> No audio card can only work if btaudio works for your cards.
>> AFAIK, there is not make/model that is sure to always work
>> much less work and have good sound quality.
>
>
> From what I've read, the WinTV model 401 works for everyone.

Well, that's about to come to an end :-(

This is the perfect example. The model number 401 was
used over several revisions and, in fact, the contents
of the package changed over time. I have two "model 401"
that are older and packaged without the remote control
and I can tell you for a fact that btaudio does not work.
Others with this rev report that it doesn't work and I
believe I've seen people have no success with a package
that included the remote.

For now ;-), I won't state that any model will be sure
to work until you buy it, install it, configure it, and
actually hear sound that you are happy with.

-- bjm