[WORKAROUND] DVB-T2: Increase in data errors after platform switch

Hauke · February 27, 2021 at 8:59 PM

Hi folks,

I'm a bit at a loss how to tackle the following problem: I use WinTV dualHD DVB-T2 receiver now since quite a while. In the past I used LePotato Amlogic device, but since the kernel did not properly support the DVB-T2 stick, I had a Raspberry Pi 3 running with a then up-to-date 4.19 kernel/Raspbian Buster and tvheadend on it, and subscribed to that from LePotato. That worked stable and very well. Only thing that annoyed me was that I needed to waste power on two devices, and when Raspberry Pi 4 came out, I switched to it and attached the DVB-T2 stick to it, with immediate success.

But ever since I have the problem that I have a lot more data errors, which result in image and/or audio glitches. I suspected power issues and now put a powered USB hub inbetween, and it currently seems as if it is better, but I still have not nearly the same stability as I had with the Raspberry Pi 3.

I've also tried all three DVB driver packeges, there's basically no difference.

I've exchanged cables, no difference.

I even have two of the receivers and changed them, no difference.

In dmsg I find repeated entries like this:

Code

[   30.296916] em28xx 1-1.4:1.0: write to i2c device at 0xc8 failed with unknown error (status=128)

I'm atually considering putting the Raspberry Pi 3 back into my network... For testing I just did, and the ic2-errors do not show up the the Pi 3's dmesg...

Any help appreciated!

ghtester · February 28, 2021 at 10:22 AM

Try latest LE 9.80 Nightly build (Index of /).

In past, I have also encountered occasional i2c errors related to DVB-T2 tuner (which stopped working then), usually after switching channel, but now it's OK.

Hauke · February 28, 2021 at 10:56 AM

Thanks, will give it a try! And will give feedback

elliottmc · February 28, 2021 at 11:29 AM

The RPi3 has has USB2, and I think it shares the USB with the ethernet. Someone will hopefully correct me if I'm wrong.

So, that could be the problem - USB bandwidth.

RPi4 has USB3, and works really well for me.

Hauke · February 28, 2021 at 1:37 PM

Hi elliottmc, you're right, and thus I'd have understood if RPi 3 would be working more unstable than RPi 4, but it's exactly other way round...

Hauke · February 28, 2021 at 8:05 PM

I just tried the nightly build, but TVheadend is unwilling to start. After installing the Addon, I cannot navigate to the tvheadend standard webpage. Also, using ps, I cant find a process for tvheadend. And, switching on debug/trace logging, there's no log created for tvheadend, which I suppose means that it never starts.

So, unfortunately I cannot check if the receiver works OK. I see no i²C errors, but I suppose they'll onyl show up when the receiver is used in earnest...

What am I missing? Anyone was able to start tvheadend with the nightly build?

Tried the oldest and newest nightly I could find for RPi4.

ghtester · March 1, 2021 at 9:26 AM

Quote from Hauke

Anyone was able to start tvheadend with the nightly build?

Of course, it works fine. Try a fresh install from scratch then.

Hauke · March 1, 2021 at 10:54 AM

Quote from ghtester

Of course, it works fine. Try a fresh install from scratch then.

Strange - I did a fresh install... Which version are you using specifically?

ghtester · March 1, 2021 at 12:16 PM

Currently LibreELEC-RPi4.arm-9.80-nightly-20210226-e12ff43.tar 2021-02-26

A couple months I am upgrading almost daily, the first upgrade was over LE 9.2.6.

There are still some issues, like with timeshift, but I never had an issue which should prevent TVheadend backend from starting.

You can perhaps also try to install Tvheadend 4.3 from ,zip ( Tvheadend nightly builds for LibreELEC ), I did not try yet and I am still running 4.2 which is part of LE 9.80 Nightly.

Hauke · March 1, 2021 at 1:03 PM

OK, thanks. I used exactly that one... Will try again. And as you reccomended try another addon version if I still do not succeed.

Hauke · March 2, 2021 at 7:37 PM

With the addon from the nightly I get tvheadend up'n'running. Unfortunately the I²C errors persist, and also the glitches Any other ideas?

Update: Just tried the 10.0 nightly, still same errors.

Hauke · March 7, 2021 at 1:05 PM

Just installed the most recent Raspberry Pi OS on my RaspPi 4 and put tvheadend on it. Interesting: The same I²C errors are there, and I've glitches...

So, I have a RPi 3 with buster, but still on kernel 4.19, and a RPi 4 with buster, but kernel 5.10. Pi 3: Works nice and stable. Pi 4: I²C errors, glitches.

Anyone has an idea what might be the change that happened that may cause the problem?

EDIT: Just put the SD card from the RPi4 into my RPI 3, so exact same OS/software/everything --> No I²C errors/Glitches. It obviously has something to do with the RPi 4 hardware/drivers...

EDITEDIT: seems to be kind of a known problem: Haupauge DualHD (em28xx) driver broken. Kernel spam "write to i2c device at 0xcX failed with unknown error" on RPi4 - Raspberry Pi Forums and there seems to be a workaround. Will try this soon and report

EDITEDITEDIT: The workaround indeed works. I²C errors remain, but TV reception is stable and I have nearly no errors in picture or audio. It's still a bit below par with RPi 3, but fully acceptable.

Hauke · March 22, 2021 at 6:10 PM

An update after a few weeks of using the setup: It is better, but still not good. The number of data errors is down quite a bit, but still once in a while they come at the worst imaginable moment. So I'll fire up the Pi 3 again and wait for further Pi 4 firmware improvements... *Sigh*