[mythtv] RFC: Dealing with overlapping video-sources/channels

[Geoffrey Hausheer]

I have two overlapping video sources setup in myth:
analog: 1-98
digital: 1- 600
the 1-98 channels are identical with a few exceptions (there are some
channels on the 'analog' that  I can't get with 'digital)
I am attempting to use my tuner-card for the analog section, and use the
S-Video in with an IR-Blaster controlling  my digital cable box for the
digital channels.

Myth is not particularly happy with this setup though.  It  has no
knowledge that channel '2' on analog and channel '2' on digital are
identical, so they both show up on the listing, and when I choose to
record 'Any showing on this channel' it will assign it to always record
off either the analog or the digital, and it won't pick the best one for
the given showing.  The whole point of this setup is to let me record 2
programs at the same time, so I'd like myth to choose whichever one is
not recording at the moment.

This seems to be a limitation of the way channels are stored (using
unique channel-ids...so channel 2 is either 1002 or 2002), and since myth
always refers to a channel by its ID, it  has no way of knowing  they are
the same.

So I'm soliciting suggestions as to how to fix this.

I had two ideas about it:
1) Use an equivalence table that maps equivalent channel-ids.

2) Create non-overlapping video-sources (in my case 'common',
'digital-only', 'analog-only') and allow a video device to be attached to
multiple sources.

option 2 is much easier to implement, however is has some drawbacks: 
specifically, fine-tuning/brightness/etc will only be defined once, so if
2 capture cards need different tuning adjustments, we're out of luck. 
The solution would be to create a new table which has only fine-tuning
information per-source, and leave the accessible channels in a different
table.

option 1 is more flexible (I could map channel 512 as being equivalent to
channel 2 for instance), but defining the equivalence table in a way that
is easy to access may be tricky (it either needs to be referenced per
'real' channel, or be cross-referenced with all cannel-ids), and it
requires a lot of modifications to the source to support the lookups.

Also to keep in mind is allowing a preference. I'd prefer that myth try
to use the analog tuner when watching livetv, since it can change
channels much more rapidly, but obviously if I want to watch channel 230
it needs to switch to digital.

.Geoff 
-- 
  Geoffrey Hausheer
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