[mythtv] What is the best way to implement overlapping recordings on one channel?

Glenn Moloney glenn062 at optusnet.com.au
Sun Apr 3 12:26:58 UTC 2005


Hi All,

Thanks for comments from everyone. Sorry to be absent for the last few
days - I've been slowed down by a nasty cold.

I will proceed with option 2 (or something like it) - though I didn't
get far over the weekend.

And thanks for the inducement David :-).

cheers,
glenn.

On Thu, 2005-03-31 at 21:49 +1000, David Whyte wrote:
> I really like the idea of one and two.  
> 
> I like the idea of one, just as I hope that soon LiveTV will be
> implemented like this so that it is a little more stable than the
> current ring buffer implementation.  This will also allow you to
> change channels and be able to rewind to where you were watching a
> previous channel.
> 
> I think two is the best way of attacking this little problem though,
> even if feature one did get implemented.  I think this would provide a
> much more stable way of being sure that you only delete the correct
> bits of recording when that time comes.  Also, you are actually
> recording *two* shows so you should get two copies ;)
> 
> I tell you what though, being a fellow Aussie (from BNE), if you get
> this implemented, let me know and I for one will buy you a carton of
> XXXX (as in Castelmeine (sp?) for the non-Aussies) or two or whatever
> your poison may be.  I am tired of only being able to record one
> channel even though I have two tuners.
> 
> Thanks mate,
> Dave
> 
> 
> On Thu, 31 Mar 2005 20:09:05 +1000, Glenn Moloney
> <glenn062 at optusnet.com.au> wrote:
> > Hi All,
> > 
> > I have a "feature" (well - I call it a feature) I want to implement:
> > 
> >       Allow overlapping recordings on one tuner.
> > 
> > I am interested in feedback on how best to implement this feacture - in
> > a manner acceptable to the mythtv powers that be.
> > 
> > I find that I need to allow at least 5 minutes (up to 15 for some
> > networks in Australia) of "overrecording" on each program. If I want to
> > record programs following each other on the same channel - I need to use
> > two tuners. I would rather not use two tuners for this job - at least
> > for the case where the same recording profile is used for both
> > recordings.
> > 
> > As I see it, there are two approaches:
> > 
> > 1: The "high-level" approach: A "recording" may be fragmented across
> > several fragments of files on disk. This means little change to the
> > low-level recording code mythtv. Also permits constructing "virtual"
> > recordings from existing recordings (eg. highlights), etc...
> > 
> > 2: The "low-level" approach: Allow the output from one tuner to be fed
> > into two files during the overlap period. One approach would be to
> > extend the RingBuffer class to allow two (or more) output files to be
> > attached to each ringbuffer. There will also be some fiddling in
> > tv_rec.h to "do the right thing" during the overlapping recordings, and
> > some changes to how we test if a channel is available for recording,
> > transferring ownership of the ringbuffer, etc...
> > 
> > 3: Copy data from the end of the previous recording into the next
> > recording. In this case, we delay the start of the second recording, and
> > copy the data from end of the previous recording file into the new
> > recording file. Needs to happen seamlessly.
> > 
> > I am favouring Option 2 - and have started planning for it.
> > 
> > Obviously there is more to it than I describe here - but you get the
> > idea. The scheduler will need to recognise that these recordings are NOT
> > a conflict (given the first feature is working correctly).
> > 
> > Any suggestions or comments welcome.
> > 


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