[mythtv-users] Silicon Dust HDHR5-4K

Gary Buhrmaster gary.buhrmaster at gmail.com
Wed Nov 4 01:54:25 UTC 2020

On Mon, Oct 26, 2020 at 6:17 PM John P Poet <jppoet at gmail.com> wrote:

> Have you looked at Gary's ExternalRecorder for the HDHR?
> https://github.com/garybuhrmaster/mythhdhrrecorder

FD: I do not have, nor do I have any current
plans to purchase, one of the new HDHR5-4K
tuners for testing (and for that matter, my
market does not currently have a transmitter
(except by press release)) so any improvements
will be based on guesses as to how to make
things work better.

While I believe that that recorder should be
able to perform recording (although playback
is still an issue), one will likely need to carefully
configure the recorders and/or videosources
and/or tuner priorities to achieve results you
will find acceptable during testing.

Some complexities (based on my current
understanding, and not personal experience

  - the HDHR5-4K has two ATSC 3.0/1.0
    tuners, and two ATSC 1.0 (only) tuners

  - In many markets the same (virtual)
    channel is used for both 3.0 and 1.0
    broadcasts from the same station.

  - In most markets, not all channels are
    both ATSC 3.0 *and* ATSC 1.0 that a
    particular combo tuner may have
    access to (some stations will be ATSC
    1.0 only on the combo tuner).

  - If a request for the new HTTP streaming
    request is made to the tuner, and if the
    (virtual) channel is available both 3.0
    and 1.0, a 3.0 tuner will be chosen if
    one is available (otherwise it will fall
    back to a 1.0 tuner if a 1.0 tuner can
    tune that (virtual) channel, but if the
    virtual channel is 1.0 only, and no 1.0
    tuners are free the device will use a
    a ATSC 3.0/1.0 tuner).

So, for the HDHR5-4K with mixed capabilities,
and for applications such as MythTV, this
can result in some artifacts that reportedly
even SD is trying to think through (should
there be a way to disable ATSC 3.0 selection
so that the ATSC 1.0 versions show through
(perhaps to allow apps that don't support
AC-4 today to still operate?), should there
be a way to make sure that the ATSC 3.0
capable tuners are *only* used for ATSC 3.0
channels if any exist in the market (so that
they don't get used for an ATSC 1.0 channel
that could be found on another tuner?),
should ATSC 1.0 stations on a mixed
capability tuner (that has any ATSC 3.0
stations broadcasting?) have a priority
lower than "normal" so that that tuner is
selected only as a last resort for legacy
stations, and lots of other possibilities).
Right now there would appear to be no
consensus as to what will work well for
everyone (and having hundreds of knobs
to adjust behavior is likely to just cause
confusion and lots of holes in feet, and is
in opposition to the "KISS" principle that
most apps are targeting).

With the latest external recorder version
(and when I say latest, I mean as of today),
the code has been modified such that
combination tuners that have active ATSC
3.0 reception will be prioritized to be used
first only for ATSC 3.0 channels, and the
remaining ATSC 1.0 channels will be
deprioritized such that the combo units
will mostly be reserved for use by ATSC
3.0 channel requests, but can still
fallback if there are not other tuners
available for ATSC 1.0 channels.  This
will not result in optimal results if one
has multiple mixed-mode tuners (we
need more control there), but it is
probably good enough for initial testing.

So, in some ideal world, converting all
your OTA HDHR tuners to use the
external recorder might mostly *just work*,
but the reality is that we currently can't
playback recordings with AC-4.

So, ignoring that right now you can't
play back any recording, what I would
recommend for record only testing
is to create two external recorders
explicitly defining the combo tuner
(and do not define the combo tuner
to MythTV), and create them with
a higher priority than your existing
tuners, and create them with a videosource
that only has the ATSC 3.0 channels
that exist in your market defined.
That will, essentially, "reserve" the
tuner(s) for an ATSC 3.0 broadcast.

Good luck.

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