[mythtv] dvb scanning

Daniel Kristjansson danielk at cuymedia.net
Thu Jun 8 20:52:59 UTC 2006

On Thu, 2006-06-08 at 22:27 +0200, Janne Grunau wrote:
> On Thursday 08 June 2006 22:01, Yeasah Pell wrote:
> > I have a few things that I'd love to get in there at some point:
> >
> > 1) PAT/PMT-only scanning.
> This was at least in parts working in somewhere after 0.19. We had 
> problems with inserting channels without names since no SDT was seen.
Actually PAT/PMT are still picked up, and only used if no SDT or NIT
is seen. Yeasah wants to ignore SDTs and NITs altogether to speed up
the scan when you know the source is not a DVB source. This should be
fairly easy to implement. You just need to add a boolean scanPMTOnly
to siscan and when it is set have HandlePAT and HandlePMT check if
the PAT has been seen and all the PMT's in the PAT have been seen.
If all have been seen call HandleMPEGDBInsertion(). Also, you need to
add something to the UI to let the user set the scanPMTOnly boolean.

> > 2) Per source channel number offset. This would allow the user to set
> > up a per-videosource offset for channel numbers that are inserted
> > into the DB (i.e. channel numbers are set to the acquired serviceid
> > plus the offset, whether those serviceids came from importing, or
> > various channel scans)
> This wouldn't be of any use by me since my service ids are distributed 
> over the whole 2^16 space.
Again this should be fairly easy to add, just look at the HandleXXXDBInsertion methods.

> > 3) This one's kind of out there, but ... optional background
> > scanning. You could set it up so that it would go and do transport
> > scans during idle time, similar to the active EIT scanner (more
> > infrequently of course, once a day or less),
> This could be integrated into the EIT scan.  
I think it should be separate from the EIT scan. To do this properly
you really need to create a list of channels to Add/Delete and let
the user choose to reject or accept each change and tell the scanner
to ignore updates on some channel which it habitually wants to delete
or add. We used to do this automatically and it caused channels to be
deleted which were just off-air because they didn't run 24x7. There are
various reasons why it should be separate from EIT scan, but two simple
reasons are not all channels get scanned in an EIT scan, and also other
transports are not scanned in an EIT scan, but an auto channel scanner
should check them out once in a while.

I can think of another thing you would want before enabling auto-scan,
filtering of channels you can't get because they use a CAM method/key
you don't have (i.e. I wouldn't want to know what channels have been
added to some network to which I am not subscribed). This means adding
CAM system checks to DVBSignalMonitor which shouldn't be too difficult,
but should be done by someone using CAM..

-- Daniel

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