[mythtv-users] Large-scale myth farm

[Rob Willett]

Illtud,

Intersting to see a UK government org taking an interest in MythTV.

I'll try and answer your questions with my experience, I can help with some
aspects but not others of your questions.


Quoting Illtud Daniel <illtud.daniel at llgc.org.uk>:


>> Hi,
>> 
>> At the National Library of Wales we're looking to implement
>> an off-air recording system to ingest into our digital asset
>> management system, and we're interested in MythTV as a front-
>> end (as it has all the scheduling smarts etc.) then ingesting
>> the datastreams & metadata from MythTV into our DAMS. I've
>> a few questions:
>> 
>> UK DVB cards/receivers - which would you recommend? We'd like
>> to be able to capture subtitles and get metadata from the EPG.
>> Direct MPEG2 capture would be the ideal, possibly transcoding
>> to MPEG4.


There seem to be a number of different DVB cards that people use. I persoanlly
use the Nebula DVB card, though other people report success with the Avermedia
771 card. One major issue with DVB cards is that manufacturers do change
chipsets with little or no notice but don't change their model numbers. If you
buy any cards, budget for a few more and then keep them as spares. I would
suggest you buy a standard card and stick with it.

All the DVB cards record the digital stream directly from the broadcast. Not
sure if this is MPEG2 or MPEG4. Please note that the file format saved is .NUV
which seems to be difficult to reprocess. 

You can setup the system to record the EPG information provided by the DVB
stream. This works pretty well, though only has a week in advance. I've never
used Subtitiles so can't say if they work.

>> 
>> FM Radio Cards - I can't see how to get MythTV to use the FM
>> function of the PVR350 we're experimenting with. How would we
>> use external tuners and a soundcard audio input for this?
>> If there's no 'video source' for the scheduling data how do 
>> we set up a channel that does nothing except record audio
>> without associated data? (and can we manually add data through
>> the fronted?)


Mythtv does not support FM radio nor does it easily support DVB radio e.g. BBC 7
without a patch. This is because there is no video send with the audio. This is
a majot pain in the butt and I wish they would change MythTv to properly support
Radio.

>> 
>> Multiple backends - I can't see an overview of how this works -
>> is there one? From what I can understand, you configure
>> additional backends with additional capture cards, and the
>> master backend farms out the capture work to the others -
>> correct? Where does transcoding take place? Are these jobs
>> shared out intelligently, or does transcoding always occur on
>> the backend which captured the programme?


Not sure that you can have multiple backends. Perhaps I've misunderstood this
but you can have many frontends onto one backend. You could reconfigure the
frontend to use different backends but I wasn;t aware that you could actually
make MythTv into a clustered farm. Kinda neet but not that useful to many people. 

You could have multiple servers, though setup independently of reach other.
Server1 handles BBC1 - 4 depending on how many cards you have.
Server2 handles ITV etc etc.

Since there are 30 or so channels you wou would need around 5-7 servers
depending on the hardware specs. My suggestion would be to use some sort of SAN
for the backend disk storage. The architecture to do all of this would be fairly
simple, but I wouldn't treat this as a 'hobby' approach. If this is an archive,
I would look at UPS's, tape backup, resiliance and redundancy etc etc. I work
for IBM, though my Myth work is personal and has no connection with IBM etc etc, 
happy to discuss further if that helps. You don't need to go overboard with
hardware but if this is supposed to stay up 24x7 then you need to be ruthless
over the build of your servers and your operation of them/.

>> 
>> Sorry to have put so many questions into one post - please
>> reply if you've answers to any of the above, I'm not expecting
>> anybody to have all the answers!
>> 
>> -- 
>> Illtud Daniel                                 illtud.daniel at llgc.org.uk
>> Uwch Ddadansoddwr Systemau                       Senior Systems Analyst
>> Llyfrgell Genedlaethol Cymru                  National Library of Wales
>> Yn siarad drosof fy hun, nid LlGC   -  Speaking personally, not for NLW



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