Guarding against a service which moves from one transponder/multiplex to another: new service is not attached to channel

Added by Martin Underwood over 3 years ago

I have a TVHeadend setup with one DVB-S (satellite) and two DVB-T (terrestrial) tuners. I've given satellite a higher priority than terrestrial because terrestrial reception can sometimes be subject to continuity errors.

I have channels configured that use all three tuners: satellite as first priority and then terrestrial as second choice if satellite is already in use.

I had a recording fail this morning - no error messages in failed or removed recordings, and a red "recording" dot when I looked during the period of the recording. But the .ts file was only a few MB in size.

It turned out that the channel I wanted had just moved from one transponder/multiplex to another existing one, a day or so earlier. In the list of services, there were four entries:

- Satellite (old frequency, attached to the channel)
- Satellite (new frequency, not attached to the channel)
- Terrestrial (first tuner, attached to the channel)
- Terrestrial (second tuner, attached to the channel)

I've rectified this now, by attaching the new-frequency service to the channel, and deleting the old service.

Does TVHeadend have a mechanism for preventing this situation from occurring when an older service ceases (and is last detected some time before the start of the recording) and a new service with the same service name is created on a new mux? I'm surprised my recording didn't even get listed after the event as a failed recording. I created the recording schedule about a week before the change of mux occurred.

As an enhancement, it would be useful if TVH would automatically try another service if the highest-priority one returned no video/audio stream data - if treat "no data" as if it were "tuner is already allocated to another recording".

Replies (3)

RE: Guarding against a service which moves from one transponder/multiplex to another: new service is not attached to channel - Added by Dave Pickles over 3 years ago

I believe that service changes from one multiplex to another are automatically handled if the DVB-S network is set up to use a bouquet. However you're then stuck with the broadcaster's choice of LCNs and his way of handling regional variants and HD / SD preference.

The decision of which service and tuner to use to handle a recording is made at the time the recording starts. There is already an option to reschedule a recording if the number of errors exceeds a preset figure, though I'm not sure that a missing service would actually generate any errors. Ideally the recording should terminate if no data was received, then immediately reschedule but with the failing service/tuner combination vetoed, so that the planned recording could continue with just the first few seconds missing.

RE: Guarding against a service which moves from one transponder/multiplex to another: new service is not attached to channel - Added by Martin Underwood over 3 years ago

Yes I've not investigated bouquets. From what I read when I first started using TVH, it sounds as if it would take a lot of the fine control of channel choices out of my hands. For instgance, I have laboriously set up all the ITV regions as separate services and channels, with a generic "003 ITV" channel (names preceded by LCN so they sort at the beginning of the list) for my local region.

You say "There is already an option to reschedule a recording if the number of errors exceeds a preset figure, though I'm not sure that a missing service would actually generate any errors". I think you've hiot the nail on the head: "no service present" (ie no streams received) does not seem to be regarded as an error condition - bizarrely - so it wouldn't trigger the rescheduling on a different tuner.

I had the same problem of recordings which appeared to be proceeding correctly (red-spot icon during the recording, no "failed recording" entry afterwards) on another occasion, when ITV suddenly withdrew most of their SD versions of ITV1 and left only the HD versions. So when I saw a very samll TS file this time, I guessed what had caused it, and Lyngsat confirmed it: Talking Pictures TV had moved from one mux to another a day or so earlier. TVH had picked up the new sevice perfectly - but it hadn't added it to the channel.

Does anyone know a site which lists satellite (and terrestrial) changes which are due to happen, describing the forthcoming changes and the date that they will take effect in advance?

RE: Guarding against a service which moves from one transponder/multiplex to another: new service is not attached to channel - Added by Dave Pickles over 3 years ago

Looking at the code I doubt it would be (easily) possible to detect an input source providing no data. When a recording is scheduled to start, TVH subscribes to the channel (which involves choosing a service and tuner) then spawns a new thread to do the recording. There is no way for the recording thread to abort in a way which could be used to trigger a subscription to another source.

An alternative is to purge the services list of entries which are no longer broadcasting. The GUI has that function under Configuration -> DVB Inputs -> Services -> Maintenance but it would be more convenient to do it automatically. It is possible to use the API; run this command using cron from a machine on your local network:

curl 'http://user:[email protected]:9981/api/service/removeunseen?days=5'

Unfortunately the minimum 'unseen' interval is 5 days, and of course if the defunct service was the only source for that channel then the recording will be missed.

Does anyone know a site which lists satellite (and terrestrial) changes which are due to happen, describing the forthcoming changes and the date that they will take effect in advance?

https://www.tvchannellists.com/Forthcoming_changes_to_digital_platforms_(UK_%26_Ireland)

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