Green Artifacts on HD Channels Tvheadend

Help and Support Raspberry Pi
41

Seems that there are other people having similar problems. I especially have problems with channels above 450mHz.
Some solved it by compilating patches to tvheadend:

On the other hand there are others confirming that it works again with some versions of Libreelec:

https://libreelec.tv/2017/02/libreelec-krypton-v7-95-2-beta/#comment-1312

42

We will move to TVH 4.2 soon.
Do I need to apply patches to this version? If so, can you point me to them

43

Here is the patch:

https://tvheadend.org/attachments/download/5142/linux-999_r820t.patch

This is the source: https://tvheadend.org/boards/5/topics/22310?r=25348#message-25348

I’m looking forward to testing the new version. This problem is bothering me for months.
Thanks.

44

That’s a kernel patch, not a TVH patch. It only seems to change behaviour for a specific DVB-C tuner. Are you using this DVB-C tuner?

45

Yes I use the Astrometa dongle. The chipset for DVB-C is the MN88473.
Before being able to use it at all I had to copy the firmware to /lib/firmware/.

46

Will you apply the kernel patch though it’s not related to tvheadend?

47

I compiled the kernel with the mentioned patch (never thought I would be able to).
Tvheadend with the cheap Astrometa dongle works now for higher frequencies without any artifacts. I will test wether this remains.
It would be nice if you could integrate this patch so that it doesn’t disapear with the next update.

48

If you can PR the patch it would be appreciated

Sam

49

Thanks for including the patch in the July update.
There are almost no artifacts at higher frequencies anymore though I’ve noticed that it is not perfect after long time watching. Moreover frequencies below 300 MHz don’t work at all.
Others should be aware of buying an Astrometa stick for DVB-C use. Maybe a Geniatech T230 is the better choice.
Are there any news regarding an officially supported (and sold) DVB stick?

50

The stick is progressing but it’s DVB-T2 not DVB-C

51

Good to know. I was assuming that most of the DVB-T2 chipsets are capable of DVB-C. Unfortunately DVB-T2 on a Raspberry Pi won’t work for German TV because of the HEVC standard.

52

It seems the guys at libreelec have found the commit that caused artifacts with the 4.9 and above kernel.

This is the commit kernel/git/torvalds/linux.git - Linux kernel source tree

Users have reported without this commit the artefacts are gone.

See here DVB issue since LE switched to kernel 4.9.x - Page 13 - Bug Reports - LibreELEC Forum

1 Like
53

Thanks for the report.

We can get this included for the next OSMC update, which is tentatively scheduled for Sunday, 7th January.

Sam

2 Likes
54

Happy to report the green artifacts gone with latest update.

Thanks to the user on the libreelec forum for hunting down the commit.

:slight_smile:

1 Like
55

The fix wasn’t added in the December update, so I’m surprised you’ve noticed any changes.

I’ve now reverted the commit that has been known to cause problems and would appreciate some testing.

To test this update:

  1. Login via the command line
  2. Edit the file /etc/apt/sources.list
  3. Add the following line: deb http://apt.osmc.tv stretch-devel main
  4. Run the following commands to update: sudo apt-get update && sudo apt-get dist-upgrade && reboot
  5. Your system should have have received the update.

Please see if the issue is resolved.

I also recommend you edit /etc/apt/sources.list again and remove the line that you added after updating. This will return you to the normal update channel.

Sam

56

Hi sam

Well i certainly noticed a difference i see tvheadend version was updated so maybe that helped.

Its still not perfect as i have to stick with the bob (x2) deinterlace as adv (x2) still has an odd glitch.

Good to know that it may improve with the commit removed. Ill give it a test.

Do you recommend me to create an image of my machine before doing the testing or is it safe to do it on my stable system.

Thanks for the update

57

Thanks Sam

Just updated things have improved alot. No issues with bob (x2) deinterlace anymore. Still slight glitches with adv (x2) but not as often as before. I may try increasing the sdram bandwidth that might help.

Although im still get continutity errors in tvheadend but doesnt seem to be causing glitches for the moment. May be my signal not sure.

I’m using omx player as its much smoother using the gui than mmal.

Thanks for update least no more tv issues for the moment :+1:

58

Probably a signal issue at this point.

59

What are the symptoms of ‘continuity errors’ if not a ‘glitch’ please?

60

Sorry yeah turns out the glitches are continuity errors. My signal appears fine. Only odd glitch now so watchable for the moment.