[SOLVED]Channel Scan – Timed out, no channels

[kmdewaal]

Hi guys,

Can you please try the attached patch which can be applied on top of the mythtv-master of today like this:

Code: Select all

cd ~/mythtv-master/mythtv/mythtv
git pull
git apply 20201111-wintv-atsc-debug.patch
make
make install

Please again the output of a scan with mythtv-setup with lots of debug on:

Code: Select all

mythtv-setup -v channel,chanscan,record,siparser --loglevel=debug 2>&1| tee my_log_file.log

FYI, what happens is the following. The tuner gets in lock and the signal strength can be obtained but the demodulator is not happy as indicated by signal/noise ratio and bit-error-rate are not available.
The calls themselves work with the DVBv5 method. The DVBv3 method for signal strength fails and that is new, otherwise MythTV v27 would never have worked. My current thinking is that this is likely to be the change why it fails. I also expect that on Ubuntu 18.04 everything works.

In the current master only control of the DVB-S/S2 and DVB-T/T2 cards was done with DVBv5 calls but the DVB-C and ATSC cards are still controlled with DVBv3 calls and that is what I am now looking at. The attached patch is very much a work-in-progress version and should not be viewed as an example on how to write software.... but I would like to have feedback.

Thanks,
Klaas.

[hutsmythtv]

Klaas and Tim,

Thanks much for the continued help! I am getting further. I can now get into mythtv-setup (and I am getting in as user "mike" - supposed to run that as user "mythtv", correct?). But I must have missed another install - mysql appears to not be installed. I try "sudo systemctl status mysql" and it replies back as that service can't be found? Doing some googling last night, I found this post (https://stackoverflow.com/questions/411 ... -in-ubuntu) and this command "sudo apt --reinstall install mysql-server" - but this won't work for build-from-source install, would it?

Mike

[bill6502]

@hutsmythtv, I left one out and all can be checked with one command. Type: systemctl status mysql mysqld mariadb

[hutsmythtv]

@Bill6502 --- Sorry, didn't like that one either.

Code: Select all

$ sudo systemctl status mysql mysqld mariadb
Unit mysql.service could not be found.
Unit mysqld.service could not be found.
Unit mariadb.service could not be found.

Mike

[timmy527]

Hi Klaas:
Patch applied ( I couldn't get the 'git apply' to work so nuked the entire mythtv subdirectories and reran the git pull, configure, make, etc... ) and
mythttv-setup run. Of note, the channel scan quickly went through all the channels and I didn't see any info on signal strength or other data... No channels found..

Please let me know if this was not what you were expecting or if I need to rerun.

Thx
Tim

[kmdewaal]

Hi Tim,

Thanks for testing. New patch attached.
The patch can be applied when the first patch is removed, so for instance like this:

Code: Select all

cd ~/mythtv-master/mythtv/mythtv
git checkout .
git apply 20201112-wintv-atsc-debug.patch
make
make install

Please test this in the same way.

Thanks,
Klaas.

[timmy527]

Thx Klaas:
Reran, guess I need to run the git checkout and apply in verbose mode, both completed with zero output.. should have checked $?...
Reran mythtv-setup, signal strength and signal/noise showed in the scan, no channels found.

Please let me know if this is providing what you need.

Thx
Tim

[kmdewaal]

Hi Tim,

The "git apply" does not give output except if there is something wrong.
The way you do the test is perfect. Next patch is attached. Only a small change which should not make any difference but maybe...
Same procedure to clear the previous patch and to apply this one.
Please try this one also.

Thanks,
Klaas.

[kmdewaal]

Hi Guys,

Can you please do a scan with dvbv5-scan and post the result?
The command for you must be something like this:

Code: Select all

dvbv5-scan -o result dtv-scan-tables/atsc/us-ATSC-center-frequencies-8VSB-062009

N.B. The dtv-scan-tables can be retrieved from linuxtv.org as follows:

Code: Select all

git clone https://linuxtv.org/git/dtv-scan-tables.git

Thanks,
Klaas.

[hutsmythtv]

Kaas,

Please see attached the dvbv5-scan for my area.

Thanks!
Mike

[kmdewaal]

This IS interesting! It looks like dvbv5-scan fails in the same way as MythTV.
Both do acquire a tuner lock and then no data is read. Which can indicate that the demodulator is not setup correctly.

Code: Select all

Scanning frequency #4 79028615
ERROR    command INVERSION (6) not found during store
ERROR    command INVERSION (6) not found during store
Lock   (0x1f) Signal= -76.00dBm C/N= 22.53dB
ERROR    dvb_read_sections: no data read on section filter
ERROR    error while waiting for PAT table

[timmy527]

Hi Folks:
Similar results on the dvbv5-scan run, attached.
Is the demodulator setup error something in our Mythtv-setup config or something in the mythtv code?

Thx
Tim

[kmdewaal]

Hi Guys,

Can you please do the dvbv5-scan again but then with the attached center frequencies file?

Code: Select all

dvbv5-scan -o result us-ATSC-8VSB-hutsmythtv-test

In this file I have removed the INVERSION lines that apparently caused the previous test to fail.
If this succeeds then the next step is to remove the INVERSION setting also from mythtv.

About your question

Is the demodulator setup error something in our Mythtv-setup config or something in the mythtv code?

This is something that the mythtv code does.

FYI, this is how it all works.
A capture card consists of a tuner and a demodulator.
The tuner tunes to a frequency and when it receives something it is in lock.
The output of a tuner is an analog signal. This analog signal then goes into the demodulator.
The demodulator is the part that convert the analog waveform into bits. The bits then go into the mythtv recordings.
The demodulator needs to know how to decode the analog signal and this has to be written into the demodulator by mythtv.
This are things as modulation system (e.g. 8VSB or QAM), symbol rate, inversion, forward error correcting code, guard interval and depending on the modulation system a few more.
If one of these settings is wrong then the demodulator will not produce bits and this is what can be the case with the WinTV card here.

Also interesting to know is that the demodulator is actually a small computer that requires its own software before it does anything. This is the firmware that is found in /lib/firmware and that is loaded into the capture card at boot (see the dmesg output). If loading the firmware fails then there is a message in dmesg.
If the firmware is not present then the demodulator does not work.
There can be also different versions of the firmware and one version might be better than the other.
It just could be that in your Ubuntu 20 the firmware is different from that in Ubuntu 18.

And then mythtv does not talk directly to the capture card; there is a driver in between. In Ubuntu 20 the driver will be newer than the driver in Ubuntu 18 so that difference can also be important.

That Kaffeine does work with your card on Ubuntu 20 means that the driver and the firmware do actually work. However, because MythTV does not work and because dvbv5-scan does not work with the standard ATSC frequency file it is certain that it has to be done differently from the way it used to be done. Figuring that out is what we are doing!

Thanks,
Klaas.

[kmdewaal]

And this is the ATSC frequencies file, with an additional .txt in the filename to allow uploading.

[hutsmythtv]

Klaas,

Here is my latest dvbv5scan using that new file.

Thanks!

Mike