[mythtv] OSX backend obstacles?

David Abrahams dave at boost-consulting.com
Sun Dec 25 17:02:42 EST 2005

David Abrahams <dave at boost-consulting.com> writes:

>> Hmm, just turned this up in a google:
>>   http://www.dvinfo.net/conf/archive/index.php/t-10828.html
>> Perhaps this "FireWireMPEG.framework" is what you are looking for?
>> "supports IEC 61883-4 transmission and reception of MPEG2-TS packets..."
> This is killa.  Now I have 2.5 days to pack for my winter break and
> get this done :)

This is the only problem I have left: the interfaces in that library
are geared towards managing things in terms of devices, but MythTv's
configuration is in terms of low-level things like firewire ports and
channels.  The Apple library lets you build up some matching criteria
(like "is an MPEG2 device") and then iterate the list of connected
devices that match.  You can then receive connect/disconnect
notifications, etc., in addition to all of the regular communication
that we'd do.  Unfortunately "firewire port number" doesn't seem to be
among the matching criteria.  There isn't even an obvious way to ask a
device "what FW port are you on?" so I don't see how to fake it.

I've spent hours crawling through Apple's code and documentation,
trying to peel away layers until I could get down to the level of
firewire ports and then re-connect to the higher-level interface, but
it's at best non-obvious.  Apple has several layers of framework
between the one you're pointing at and the lowest-level part that can
be used outside the kernel, and it's very difficult to see through
them all.

It seems to me that the higher-level interface to device selection
would ultimately be a better one for MythTv, and I thought about
trying to change it (at least for MacOS) so that in mythtvsetup users
would just select their cable box (or other device) from a combo box.
However, there's a whole other layer of challenge I'm not ready to
face yet: Qt interfaces and working with SQL.  If anyone out there has
the expertise and willingness to help with that part, I'd be grateful.
In the meantime, I think I'm going to make the Mac code work with the
first device it can find from which it is possible to capture video.

Dave Abrahams
Boost Consulting

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