[mythtv] HD-PVR and multirec

John P Poet jppoet at gmail.com
Sun Feb 21 16:18:17 UTC 2021

On Sat, Feb 20, 2021 at 10:40 AM David Engel <david at istwok.net> wrote:

> On Sat, Feb 20, 2021 at 05:13:06PM +0100, Klaas de Waal wrote:
> > Hi,
> >
> > The HD-PVR is a card that encodes an incoming video signal.
> > It does not have a tuner, it does not receive a multiplex and hence it
> > cannot support recording different programs
> > from one multiplex. It might in principle support simultaneous recordings
> > of the same channel; this can happen
> > when recordings of different programs are scheduled to overlap.
> >
> > MythTV behavior for multirec is controlled by two fields in table
> > capturecard:
> > reclimit         This is the "Max Recordings" option in mythtv-setup
> > schedgroup  This is the "Schedule as Group" option in mythtv-setup
> > The default value for reclimit is 2.
> > The default value for schedgroup is 1 (true).
> >
> > For DVB capture cards, with tuners, the reclimit and schedgroup values
> can
> > be edited in mythtv-setup
> > page "Input Connections" / "Interactions Between Inputs".
> >
> > For HD-PVR cards the "Interactions Between Inputs"  page does not show
> the
> > "Max Recordings" and the "Schedule as Group" fields.
> >
> > When "Schedule as Group" is selected then the scheduler will create
> > additional virtual tuners (capturecard entries)
> > when needed for multirec.
> >
> > When a new HD-PVR tuner is created there is only one entry added to
> > database table capturecard.
> > The value of reclimit is 2 which indicates there should also be a second
> > entry. For DVB cards there are two entries after the "Save and Exit".
> > The value of schedgroup is 1 (true) which indicates that additional
> virtual
> > tuners (entries in capturecard) can be created dynamically.
> > This currently fails on HD-PVR cards.
> >
> > Overlapping recordings on the same channel is supported for DVB cards.
> > I think that this should also be supported for HD-PVR cards.
> >
> > If this is supported for HD-PVR cards, or if it will be supported, then
> the
> > mythtv-setup page needs to be changed so that the
> > "Max Recordings" and "Schedule as Group" fields can be configured.
> > Also the number of entries in capturecard will then be what is configured
> > in "Max Recordings".
> >
> > If overlapping recordings on the same channel is NOT supported for HD-PVR
> > cards and if this will not be added then the
> > mythtv-setup page is correct but the value for "Max Recordings" must then
> > be 1 and the value  for "Schedule as Group" must be false.
> >
> > I would like to ask if my understanding of the HD-PVR and the current
> > behaviour of MythTV with this card is correct,
> > and what the idea is of what the correct behavior should be.
> > The next step is then of course to fix it.
> >
> > N.B. SImilar problems have been reported for "V4L2 Encoder" capture
> cards,
> > This has reportedly been fixed by setting reclimit to 1 and schedgroup
> to 0.
> >  I might take that along as well.
> I thought multirec is supposed to work for HD-PVRs.  I'm not sure
> about other V4L tuners.  John Poet should be able to definitively
> answer this.  My understanding is this should all be controlled by
> CardUtil::IsTunerSharingCapable().  It doesn't currently include HDPVR
> so I could be mistaken about it's capabilities.
> David

For capturing from a HD-PVR(v1) MythTV uses the mpegrecorder which does not
support multirec. If we are talking about the newer HD-PVR2 then it works
via an ExternalRecorder which does support multirec.

At one point I worked on creating a multi-rec capable V4L2 recorder and the
code is there, However, for various reasons I ended up removing all such
devices from my system and cannot guarantee that code works or is complete.
It has been on my TODO list to re-visit it, but I have never gotten around
to it.

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