How to find DVB time or update system date programmatically

tilgrieog

Okay, I've now lost enough hours of my life on this problem it's finally time to ask for help.
This qn has come up on various forums but either no soln given or the old one now doesn't work.

I'm using TVH on a dedicated Pi running Libreelec as a TV server (version 4.3-2180 ~ LibreELEC Tvh-addon v12.0.0.0), and both server/clients have no permanent internet access. I wish for date to be updated from DVB source.
(Yes I know DVB is unreliable but better than no source.)

There are references to "dvbupdate" function in both UI screens and via CLI but in my addon no such option exists in Kodi or in TVH UI. This thread mentions it but may be out of date:
https://tvheadend.org/d/2727-time-update-function.

So, I set about finding the DVB date elsewhere in TVH and thought to write a script to update system time. I started playing with JSON API and found time in <host>/comet/poll. Taught myself to get and parse JSON data and updated time, and then started crying to discover this value is in fact the system time, not from DVB.

The web UI has the option to display time in the header, and this is indeed the DVB time. But I feel like scraping that value is clunky/beyond my skills/prone to failure.
If I had to botch something up I could schedule TVH to do something according to DVB time and compare the system time offset and go from there. N.B. I'm clearly not a programmer but when desperate enough will get dangerously creative or worst case teach myself to code. But a RTC for the Pi is ~$6 so I'd really love to just do this elegantly to prove it can be done...

Is there ANYWHERE within TVH CLI, API, file system etc etc which I can access from the shell that shows me what time it thinks it is according to DVB network (or have it update system for me), without getting my hands dirty in code or UI scraping?
Appreciate any help.
And P.S> My warmest thanks for donating your time for a great product.

DeltaMikeCharlie

tilgrieog - Provided that you can get a copy of dvb-apps for your Raspberry Pi, here is a script that I came up with today. It needs to be run before TVH starts, or, you will need so add a command to disable your first adapter at the beginning and enable it again at the end.

#!/bin/bash
#Sample script for getting DVB time and setting the
#Linux time accordingly.
#Most of the 'echo' statements are for debugging
#and can be commented or removed.
echo "Starting zap"
#'tzap' is for terrestrial tuners.  Edit this to use the
#appropriate 'zap' for your system.
#The channels.conf file comes from w_scan with the '-X' parameter.
#The name of the channel can to be hard-coded to 
#be a reliable channel in the user's channels.conf.
( tzap -r -c channels.conf 'ABC TV(ABC)' > /dev/null 2> /dev/null )&
#Or you could just take the first channel and hope for the best.
#first_channel="$(head -1 channels.conf|awk -F ':' '{print $1}')"
#echo "First channel = $first_channel"
#( tzap -r -c channels.conf '$first_channel' > /dev/null 2> /dev/null )&
zapid=$!
echo "Zap process number $zapid"
echo "Getting date/time"
#dvbdate can set the time, but it seems to assume that local is UTC
#which is not what I want.
#Note: Allow enough timeout for time source as
#not all broadcasters broadcast the time
#at the same interval.
dvbtime="$(dvbdate --timeout 61)" # --set --force
echo "DVB Date = $dvbtime"
dvb_year="$(echo $dvbtime|awk '{print $5}')"
dvb_time="$(echo $dvbtime|awk '{print $4}')"
dvb_day="$(echo $dvbtime|awk '{print $3}')"
#Note: This zero-pads the day number.
dvb_day="$(printf '%02d' $dvb_day)"
dvb_month_name="$(echo $dvbtime|awk '{print $2}')"
#This 'case' statement may need to be translated.
#This was needed because on my busybox-based
#system I could not find the right tool
#to convert the month name to a number.
case $dvb_month_name in
  Jan|January)
    dvb_month="01";;
  Feb|February)
    dvb_month="02";;
  Mar|March)
    dvb_month="03";;
  Apr|April)
    dvb_month="04";;
  May)
    dvb_month="05";;
  Jun|June)
    dvb_month="06";;
  Jul|July)
    dvb_month="07";;
  Aug|August)
    dvb_month="08";;
  Sep|September)
    dvb_month="09";;
  Oct|October)
    dvb_month="10";;
  Nov|November)
    dvb_month="11";;
  Dec|december)
    dvb_month="12";;
  *)
    dvb_month="00"
esac

echo "DVB year = $dvb_year"
echo "DVB time = $dvb_time"
echo "DVB day = $dvb_day"
echo "DVB month name = $dvb_month_name"
echo "DVB month number = $dvb_month"

set_string="$(echo $dvb_year.$dvb_month.$dvb_day-$dvb_time)"
echo "---- OS Date Before ----"
date -u
date
echo "Set string = $set_string"
#Set the Linux clock, but using UTC as the value,
#not local time.
date -u $set_string
echo "---- OS Date After ----"
date -u
date
kill -9 $zapid

DaveH

The OP said:

tilgrieog both server/clients have no permanent internet access

So I think that's why NTP isn't being considered and why DMC suggested getting an RTC. That could serve the whole network of course.

Flole

Configuration > Base > All the way at the bottom. You can enable an time Server in Tvheadend which provides the time, or you can tell it to directly update the system time. When you have different channels on different transponders that time may have an offset and you'd have the time jumping between channel switches, which might be annoying.

DeltaMikeCharlie

Flole Configuration > Base > All the way at the bottom.

To see that option, your 'Default view level' (at the top of that same page) must be set to 'Advanced'.

Flole When you have different channels on different transponders that time may have an offset and you'd have the time jumping between channel switches,

This exact thing happened when DTV was first introduced in my country. Eventually, the PVR that I was using had to be switched to 'Manual Time' (internal RTC) to stop the system time from jumping every time the channel was changed and messing up times recordings.

I would really consider getting an RTC for your Pi.

tilgrieog

Flole Configuration > Base > All the way at the bottom. You can enable an time Server in Tvheadend which provides the time, or you can tell it to directly update the system time.

Oh my god thank you!! I can't believe I missed this because I swear I looked everywhere and assumed I was seeing all of the options, and just figured either Libreelec addon was different or the option had disappeared, but it was this:

DeltaMikeCharlie To see that option, your 'Default view level' (at the top of that same page) must be set to 'Advanced'.

On my version this shows up on 'Expert', not Advanced.
Thank you for the extra info. For now I'll take a look but at least in Australia I've been pleasantly surprised most channels seem to agree on the time and, even more surprisingly, programs being out-of-schedule seems to be a thing of the past.
I suspect I will just get a RTC, but I'll ramble a bit about my setup (feel free to ignore the rest 🙂)

-I have one Pi running Libreelec with TVH server addon and a Sony Playstation PlayTV. I don't like this setup because support for TVH always seems to suggest things that don't work with Libreelec, like for example I can't install anything from the shell without an addon. I can't remember exactly why but the Pi was sluggish when I installed Raspberry Pi OS, and I'm honestly a total beginner with Linux so I just run LE because I know it best and my instinct tells me LE might be slimmer than a desktop-oriented OS. But I don't need Kodi on the server so if you can suggest the most efficient reliable OS for that server which does TV serving and nothing else, I'd be curious.

-I have more than one Libreelec/Pi TV "client" in the house which watch TV from server over network but at times neither server nor client have internet. So if I'm buying RTCs it would be frugal to have one timekeeper on the network and the others follow that if internet is unavailable.

-The main issues I've encountered are with the "client" Kodi boxes not having the correct date, so thereby the EPG is 5 years in the past and obviously shows nothing. By contrast I am impressed that it seems like TVH does everything by DVB time so even though the server system time is wrong, TVH gets all its recordings correct. On the client box I can certainly play live TV even if the date is wrong, but it cannot record live TV because, by my surmising, I think when I hit "record" the Kodi client addon tells the server a start/stop time according to the client's (wrong) system time. This is curious to me, because I've wondered would it be safer for the client to tell the server, "Hey, whatever you are playing, start recording now and stop when you think this program stops." (In other words, direct the server to record according to its internal DVB time.) This would follow more what happens when I access the TVH web UI because, as mentioned, I can start and stop any recording without issue on TVH web UI and even if the system time is wrong, it presumably gets it all done perfectly with DVB time. By contrast it seems the Kodi client says, "No. You start and stop at the time I tell you", which in this case is the wrong time.

I welcome any more discussion! Thanks again and sorry I only just saw these replies as by default wasn't 'following' the thread.

DeltaMikeCharlie

I have never used these, but there are some 'Linux TV' apps that may be able to help.

https://www.linuxtv.org/wiki/index.php/LinuxTV_dvb-apps

As part of your startup process, before TVH runs, you could run 'dvbdate' to get the current date/time. In order to do that, you will first need to run one of the 'zap' utilities to tune to one trusted mux.

chewitt

LE shouldn't have issues with time unless something is blocking NTP requests to external sources, in which case the solution is either to request time from an internal source (the router, typically). Or you fit a US$5 RTC chip to the RPi board.

https://github.com/LibreELEC/LibreELEC.tv/pull/9987 might be of interest once I finally get around to finishing a couple of items and get it merged; it's basically an alternative LE-based distro that runs Docker instead of Kodi so you have a lightweight and intentionally simple OS environment (and the same lack of package management) but with the latest self-contained Tvheadened Docker container providing everything needed.