[mythtv-users] Ceton vs multirec questions

[f-myth-users at media.mit.edu]

    > Date: Thu, 29 Jul 2021 04:15:16 +1200
    > From: Stephen Worthington <stephen_agent at jsw.gen.nz>

    > My experience with encrypted DVB-S(2) channels is that if you scan the
    > multiplex, you see all the streams for all the channels as the headers
    > for the channels are not encrypted.  But the data in the streams for
    > each channel is encrypted.  So unless there are non-encrypted channels
    > there is no ability to use multirec to record from more than one
    > channel at once as the cablecard will only decrypt one channel at a
    > time.

Now this makes sense.  I hadn't realized I'd be seeing headers for
streams which were themselves encrypted.  It also makes sense why
it appeared that precisely one stream in any TS was playable with
mpv while I was testing---it was the stream corresponding to the
channel which was currently being decrypted.

    > There is one exception to this, which I see with my encrypted IPTV
    > channels.  If you set an IPTV tuner to normal multirec and tell it
    > that it has 2 multirec tuners, and then record programmes back to back
    > with overlapping pre- and post-roll periods, the IPTV tuner will use
    > the two multirec tuners to record the two separate programs from the
    > one IPTV stream, rather than using a second (different) IPTV tuner for
    > the second programme.  I am not sure if this is also possible with
    > ATSC tuners, which are very like my DVB-T tuners.

It appears from Peter's response that they may be doing this.

    >                                                    My DVB-T tuners if
    > set with 2 multirec tuners will do that overlap trick where needed,
    > but they will also record from two different streams on the same
    > multiplex using the 2 multirec tuners.  If your Ceton tuners try that
    > with a cablecard it will not work.

Hopefully myth is smart enough not to try that.  Presumably we'd have
heard the screams if it did. :)

    > What you need for a cablecard is for attached ATSC tuners to be able
    > to be set to only use multirec for overlapping programmes on the same
    > channel, and I do not know of any option that does that.

It may be happening automatically based on what Peter said.

(And now that I know it's possible, I can also arrange a test:  Clear
the card table [hence clearing the virtual tuners as well], redo it with
only a single tuner available, and schedule two manual recordings on the
same channel with overlapping times.  That should tell me what's going
on by whether both output files appear and whether a virtual tuner pops
into existence.  But I may not have to run that test if people are
confident that this should be possible and that myth is doing so.)