[solved]Live TV with permanent TXTTV

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jensk
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[solved]Live TV with permanent TXTTV

Post by jensk » Fri Jun 05, 2020 1:51 pm

I have been running mythtv on Danish freeview on DVB-T for many years without problems My tuners have been HDHR-3 and HDHR-4.
After the transmitter shiftet to DVB-T2 i have retuned my setup to the new frequencies and everything i working - except the on the to national channels Myth tries to show a TXT-TV page that is not there - page 799 - an it does so permanently - i can't turn it off so my live tv and recordings from these to major channels looks like
Skærmbillede fra 2020-06-05 15-21-39-small.png
Skærmbillede fra 2020-06-05 15-21-39-small.png (168.49 KiB) Viewed 386 times
The black line in the top says "P799 Page does not exist"

If i use HdHomerun app on my linux pc and tune to the same channel and stream through VLC and i get a clean picture like:
Skærmbillede fra 2020-06-05 15-23-56-small.png
Skærmbillede fra 2020-06-05 15-23-56-small.png (153.18 KiB) Viewed 386 times
The problem is the same for recordings. All my recordings gets the black line with the P799 Page does not exist.

I have tried to delete all cards and make new, alle inputs and all connections have been deleted. When scanning for new frquencies i notices that i had to scan to a specific frequency 626000000 to get the channels. If i scanned all with settings to "danish" Myth did not find the cahnnels.
Then when i try to tune via HDHomerun appication on my desktop i have to stop tuning on the specific channel nr. to make the tuner detetc the
channels on the spcific channel no. Can this slowly detection have a influence on Mythtv's trying to open a TXT-TV page permanently?

I am running mythtv 31+fixes on ubuntu 18.04 on the backend and Lubuntu 20.04 with myth 31+fixes on all my frontends.
My tuner is now the sole HDHR-4
Last edited by jensk on Fri Jun 19, 2020 3:50 pm, edited 2 times in total.

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kmdewaal
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Re: Live TV with perḿanent TXTTV

Post by kmdewaal » Fri Jun 05, 2020 5:45 pm

A "Full Scan" with country selection "Denmark" should find all your channels. Other locale selections should not make a difference for channel scanning. However, it might be necessary to adjust the frequency list for Denmark if there is something changed. Which country setting have you used to do the scan? Maybe there is a website with all the frequencies and modulation schemes that are used in Denmark?
It is also a good idea to have the latest firmware on the HDHomeRuns.

I do not have clue why it should try to open a TXT page all by itself. I think that is a separate problem but I cannot rule out there is something in the stream that triggers this. To investigate this I need a full transport stream capture of at least 1GB (5 minutes) but maybe it is better to fix your channel scanning first.

jensk
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Re: Live TV with perḿanent TXTTV

Post by jensk » Sat Jun 06, 2020 2:53 pm

I have tried to scan both a specific transport 626000000 Hz and scan with the setting set to "Denmark".
When the setting is set to full scan selection "Denmark" it does not find any channels initially.
If i scan the specific frequency 626000000 Hz i can get the channels if I at the same runs HDhomerun and stop it's scanning at channel 40 (the same as 626000000Hz. Then Mythtv finds the channels.
To me it seems like the HDhomerun HDHR4 is a bit slow in detecting what channels there are at a specific frequency and mythtv scan just register that there are no channels - except when they are detected by HDhomerun in advance.

My HDHR-4DT has the newest firmware 20200521

The setup of the Danish DVT-T2 is
DVB-T2 (pr. 1.4.2020)
FFT-size: 32 Ke
Modulation: 256-QAM
Båndbredde 8 MHz
FEC code rate 2/3
Guard interval ¼
Pilot pattern: PP2

How do i make a full transport capture?

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kmdewaal
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Re: Live TV with perḿanent TXTTV

Post by kmdewaal » Sat Jun 06, 2020 4:59 pm

If it is just the HDHomeRun being a bit slow you can try extending the timeout values. Change the signal timeout to 10000 (10 seconds) and the Tuning Timeout to 20000 (20 seconds). Which should be more than enough time. The HDHomeRun devices do figure out the modulation scheme all by themselves, as I understand it by trying all possible combinations of tuning parameters. If your tuning scheme is the last one tried it may take a while. It is also possible to give more explicit tuning commands to HDHomeRun but that is now only done for DVB-C and not for DVB-T/T2.

About making a full transport stream capture. When your scanning works, do a new scan and select the "Add Full Transport Stream Channels" option. This will create an additional MPTS_xxx channel for each transport. This should also work if you do a rescan of a single transport. Then create a recording of the MPTS channel with the "Manual Schedule" option of 5 minutes. If you have gmail you can just mail that to me.

jensk
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Re: Live TV with perḿanent TXTTV

Post by jensk » Sun Jun 07, 2020 4:39 pm

If i set the timeout parameters as you note - and the channels are found when doing a full scan - Denmark.
Before scanning i deleted all channels and restartet the backend
Unfortunately the TXT-TV P799 error is still there after the scan.

I have done the full transport capture. You can download the file here:
https://www.kjellerup-hansen.dk/nextclo ... eSEtGxnfFD
Last edited by jensk on Wed Jun 10, 2020 5:57 am, edited 1 time in total.

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kmdewaal
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Re: Live TV with perḿanent TXTTV

Post by kmdewaal » Mon Jun 08, 2020 5:42 pm

OK so the channel scanning problem is solved with 10s/20s timeout values.

Downloading the transport stream was easy, I did look at it with my analyzer and it does look good, there are also teletext pages but not page 799. I do not see anything strange there. As a next step, can you please post a recording of one your problematic channels?

jensk
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Re: Live TV with perḿanent TXTTV

Post by jensk » Wed Jun 10, 2020 5:40 am

Yes - channel scanning is solved - thank you.
I have made an recording but while doing it i noticed that the preview i the frontend did not show the P799xxxxxx TXT tv message. I tried the recording .ts file in VLC and it also does not show the missing TXT tv page missing message.
This is the screendump of the frontend preview screen of the same recording:
Skærmbillede fra 2020-06-10 07-29-27.png
Skærmbillede fra 2020-06-10 07-29-27.png (214.93 KiB) Viewed 309 times
The recording of the show can be downloaded here:
https://www.kjellerup-hansen.dk/nextclo ... eR95C8sHZA

So i gues this nails down to the two questions
Why does the frontend show this error message P799 xxx when other players does not?
and
Why does this error appear on all recording made after I changes to the new DVB-T2 coding on the 2. june 2020?

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kmdewaal
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Re: Live TV with permanent TXTTV

Post by kmdewaal » Wed Jun 10, 2020 9:33 am

I can reproduce the problem. On my system the recording plays OK without the P799 error message but when I select subtitling then I get the P799 error message.

There is an option to show subtitles by default and most likely this option is enabled on your system.
This setting is in: Mythfrontend Main menu / Setup / Video / Playback OSD / Always Display Closed Captioning or Subtitles.
If you disable this option then I expect that playback will be correct without the "page 799".

In the playback menu (press M while playing) select Subtitle and then you can Disable Subtitles (when they are enabled) or Enable Subitles (when they are disabled). You can also press the T to toggle between showing subtitles or not.
When the subtitles are enabled then it tries to show subtitles from the teletext page 799. Which is not present and then you get the error message.

As I understand it, you get the error message on this recording because A. subtitle is selected, B. there is no DVB subtitling present, C. there is Teletext in the stream and D. there is no page 799 in the Teletext.
I do not know why it wants to show page 799 when you select subtitling, have never looked into this. Could be a bug or a missing feature.

jensk
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Re: Live TV with permanent TXTTV

Post by jensk » Wed Jun 10, 2020 3:54 pm

HI kmdewaal..
Thank you so much - this solved the isues. Everything looks normal now.
I noticed that mythtv now has two ways to show subtitles now. The one method is the usual where subtitles are specific subtitles after the DVB standard. and the other is through TXT TV.
The TXT Tv method is the one that is turned on in the default installation of the Frontend.

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Steve Goodey
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Re: Live TV with permanent TXTTV

Post by Steve Goodey » Wed Jun 10, 2020 4:54 pm

Hello,

If you're happy with the fix could you possibly added [Solved] to the subject line in the first post?

Ta.

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mark_k
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Re: Live TV with permanent TXTTV

Post by mark_k » Thu Jun 11, 2020 7:49 am

Not that it is in anyway helpful - but mediainfo reports teletext subtitles on page 799 - as well as something on page 398 (subtitles for hearing impaired)

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kmdewaal
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Re: Live TV with permanent TXTTV

Post by kmdewaal » Thu Jun 11, 2020 8:21 am

Which suggests that it can indeed be a bug or a missing feature.

jensk
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Re: [solved] Live TV with permanent TXTTV

Post by jensk » Fri Jun 19, 2020 3:52 pm

First - thank you for your help. It is great to have mythtv back in good order.

May I suggest that this feature OSD TXT tv default setting is "off/unchecked"

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