[mythtv-users] is (clearqam) channel scanning idempotent?

[Brian J. Murrell]

On 11-08-03 07:52 AM, Eric Sharkey wrote:
> 
> If a channel existed in the table before the scan, and the channel
> doesn't fail to tune during the scan, then the information in the
> table for that channel isn't altered.

Yeah, it's that "doesn't fail to scan" situation that makes me nervous.

> Rescanning without first deleting all channels will only affect
> channels that are either no longer tunable or are new channels without
> an entry in the database.

Good.

> The last time I did a rescan (about 6 months after the previous scan)
> the channel layout was almost entirely different, so I was basically
> starting from scratch anyway.  YMMV.

Yeah, my cableco's "moves" don't seem to be so dramatic -- I guess so
long as I don't wait for too many "moves" to happen before rescanning again.

> Moved channels appear as a deletion and an addition.  MythTV has no
> way to know that the channel which was deleted is related to the new
> one added, so you need to reenter any information you want to identify
> the channel.

I don't know about the greater community of cable providers, but mine
typically, when they move a channel, the program id stays the same and
they just move it to another channel.  Perhaps the Myth channel scanner
can take advantage of that.  Perhaps with a confirmation step in there.

> The cable providers are perfectly capable of labeling their channels
> in a way that a clear qam tuner can read,but if users could just plug
> in any old TV and find the channels they want to watch, people might
> not rent as many STBs, so they're disincentivized to do so.

Yes, very much agree.  I guess I just think/hope that Myth could be more
friendly than it is currently with scanning and associating channel
names/xmltvids.

So, if I wanted to re-scan but wanted to ensure I had all of the
information I needed to restore things to the pre-scan state, is the
channel table the only table I need to take a dump of?  Even without any
mistakes, given that I can use the progid of the digital channel to
identify moves having that information after the re-scan would probably
make my life easier anyway.

Cheers,
b.

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