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

John McEntee john at mcentee87.freeserve.co.uk
Sun Apr 3 18:38:50 UTC 2005

Can I make a little suggestion. Please could you bare in mind that DVB 
cards could use this to record several  channels on the same multiplex 
like this not just the one channel,  I believe it is one the todo list, 
but I don't think it has been started excpet for the database changes.


Glenn Moloney wrote:

>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 :-).
>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,
>>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
>>>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.
>>>mythtv-dev mailing list
>>>mythtv-dev at mythtv.org

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