Noise / artefacts when playing back 4K HEVC video on RPi4 + LE 9.2.1 (no problems on LE 9.2.0)

rpistutters · May 14, 2020 at 2:32 PM

Hello,

I am experiencing artefacts and noise when playing back a range of different HEVC 4K videos. I've been unable to identify what makes one video faulty, while another one is fine.

This only occurs on LibreELEC 9.2.1. When running on LibreELEC 9.2.0 it's fine.

I'm using the Plex addon. The client (RPi4 on LE) is configured to 'direct play' and is marked as 'HEVC' and '4K' capable. The Plex server confirms it's direct playing to the client when I playback.

Sample 10sec clip that exhibits the problem (link should remain valid until May 28th): sample

Some pictures of the issue (taken while playing the sample clip from above) can also be seen at: Imgur: The magic of the Internet

Hope this helps to narrow down what's going on, and thanks for all your works.

EDIT: Resolution has been found! Huge thanks to HiassofT and the RPi devs.

Quote from HiassofT
Good news, RPi devs found the issue and fixed it in the latest firmware. I've just confirmed that the sample plays without artefacts with it.

Please switch to LE 9.2.1 again and run these commands to update to the latest firmware:
Code
mount -o remount,rw /flash
wget -O /flash/start.elf https://github.com/raspberrypi/firmware/raw/a6c9b6b/boot/start4x.elf
wget -O /flash/fixup.dat https://github.com/raspberrypi/firmware/raw/a6c9b6b/boot/fixup4x.dat 
After rebooting the firmware version should be May 22 2020:
Code
xbmc:~ # vcgencmd version
May 22 2020 21:12:25 
Copyright (c) 2012 Broadcom
version 4da3e1264076308eda90652cb98b553ae0586390 (clean) (release) (start_x)
Please also check with your other problematic files that showed artefacts if they are fine, too.

so long,

Hias
Display More

makjade · May 15, 2020 at 4:34 AM

Hi, i have exact same problem as above poster on RPI4 LibreELEC 9.2.1.

I get a white line above with white snowy artifacts coming down from the top, same as images from above poster.

Its happens when i use the plex addon or just kodi.

It fixes the issue when i uncheck 4K capable and leave the others checked such as HEVC and direct play etc.

I'm guessing unchecking 4K reduces quality to 1080p though.

Thanks.

danioj · May 15, 2020 at 8:02 AM

I know this will not help debug the issue, however I am having the same issue with version LibreELEC 9.2.1.

I've just purchased a Raspberry Pi 4B with 4GB RAM to replace my Intel Celeron NUC (to save Plex from having to transcode). I utilise Plex Kodi Connect Add-On to access my media library via the Kodi interface. The Add-On is using the default settings (i.e. Direct Play no transcode etc). I have checked on Plex dashboard to confirm that the client is in fact Direct Play'ing the video.

Installed LibreELEC from the Pi imager application and the install tested fine with the following video:

HEVC (3840x2160) (02:41:10) MLP FBA

I then got the upgrade notice and dutifully upgraded to 9.2.1. The same video now tears and or is choppy / pixelated etc (not sure the best way to describe it). I have tried it with two other videos that exhibit the same problem:

HEVC (3840x1604) (02:28:26) E-AC-3

HEVC (3840x2160) (02:42:13) TrueHD

Downgrading back to 9.2.0 sends me back to playback heaven.

aergo · May 15, 2020 at 11:23 AM

I have this same issue playing x265 1080p 8-10bit content.

if I drop the res of my 1080p files by half it disappears.

if I change the codec from x265 to x264 it also fixes the problem.

I have only seen the problem with NTSC. but have 4k NTSC that work fine...

I have a pal 1080p 10bit video with much higher bitrates which does not suffer the same artifacts.

rpistutters · May 15, 2020 at 12:24 PM

this thread looks interesting: LibreELEC Pi4 Refresh-rate problem

will try and test this weekend to see if I can correlate refresh rates to this issue between the two LE versions.

**HiassofT** · May 15, 2020 at 2:12 PM

Thanks for reporting, I could reproduce the artefact issue with the sample file and narrow it down when that started. I've forwarded the info to the RPi devs (it's an RPi firmware issue) who'll look into it.

so long,

Hias

danioj · May 15, 2020 at 10:00 PM

Quote from HiassofT

Thanks for reporting, I could reproduce the artefact issue with the sample file and narrow it down when that started. I've forwarded the info to the RPi devs (it's an RPi firmware issue) who'll look into it.

so long,

Hias

Thanks for posting.

Would you mind elaborating on the problem with the Rpi firmware and why the firmware would cause the behaviour in 9.2.1 of LE and not 9.2.0. What changed between versions?

I assume the Rpi dev will get back to you direct. Would you confirm that when that occurs you will update this post?

Until then, I guess those of us that require playback of such impacted video are stuck on 9.2.0. Surprised this was missed in testing.

**HiassofT** · May 16, 2020 at 9:46 AM

Current theory is that the vc_image change to add 16 lines in the Jan 30 firmware is causing the issue. With the firmware before that (Jan 22) the video is rendered without artefacts.

I regularly test with a couple of HEVC videos and all these played fine on 9.2.1 and also current 9.2 development versions with latest firmware/kernel. Could be that the issue is triggered by some video properties (10bit vs 8bit / height etc) so these things can easily be missed.

One problem with the RPi video dirvers used in LE9.2 is that too many things are handled in the closed-source RPi firmware so only the RPi devs can really debug these things. As that's not ideal the current development effort is to move away from that to a fully open source video driver where everything is handled in the linux kernel. It's not finished yet but already working quite good and current LE10 test builds with it also don't have the artefact issue.

I'll report back when we get something to test from the RPi devs, until then just keep using LE 9.2.0.

so long,

Hias

rpistutters · May 16, 2020 at 11:37 AM

fantastic thank you for your time, effort and the feedback provided.

really appreciate it!

danioj · May 20, 2020 at 11:12 AM

Hias, thank you for the thoughtful and detailed reply and for your commitment to report back when the time is right. I appreciate it.

**HiassofT** · May 22, 2020 at 10:54 PM

Good news, RPi devs found the issue and fixed it in the latest firmware. I've just confirmed that the sample plays without artefacts with it.

Please switch to LE 9.2.1 again and run these commands to update to the latest firmware:

Code

mount -o remount,rw /flash
wget -O /flash/start.elf https://github.com/raspberrypi/firmware/raw/a6c9b6b/boot/start4x.elf
wget -O /flash/fixup.dat https://github.com/raspberrypi/firmware/raw/a6c9b6b/boot/fixup4x.dat

After rebooting the firmware version should be May 22 2020:

Code

xbmc:~ # vcgencmd version
May 22 2020 21:12:25 
Copyright (c) 2012 Broadcom
version 4da3e1264076308eda90652cb98b553ae0586390 (clean) (release) (start_x)

Please also check with your other problematic files that showed artefacts if they are fine, too.

so long,

Hias

harun-cuk17 · May 22, 2020 at 11:03 PM

I updated today the firmware but I have 20 april 2020 or 24 april.

I did do this with raspbian

myrpi · May 23, 2020 at 7:56 AM

You have to do that on the system booting and running LE not on separate install because old boot: files fixup.dat and start.elf have that bug and will be replaced with good new one.

Tested and working 110%

Shazb0t · May 24, 2020 at 2:33 AM

Quote from HiassofT
Good news, RPi devs found the issue and fixed it in the latest firmware. I've just confirmed that the sample plays without artefacts with it.

Please switch to LE 9.2.1 again and run these commands to update to the latest firmware:
Code
mount -o remount,rw /flash
wget -O /flash/start.elf https://github.com/raspberrypi/firmware/raw/a6c9b6b/boot/start4x.elf
wget -O /flash/fixup.dat https://github.com/raspberrypi/firmware/raw/a6c9b6b/boot/fixup4x.dat 
After rebooting the firmware version should be May 22 2020:
Code
xbmc:~ # vcgencmd version
May 22 2020 21:12:25 
Copyright (c) 2012 Broadcom
version 4da3e1264076308eda90652cb98b553ae0586390 (clean) (release) (start_x)
Please also check with your other problematic files that showed artefacts if they are fine, too.

so long,

Hias
Display More

I had the exact same issue and this resolved it. Thanks for posting!

harun-cuk17 · May 24, 2020 at 5:13 PM

Quote from myrpi

You have to do that on the system booting and running LE not on separate install because old boot: files fixup.dat and start.elf have that bug and will be replaced with good new one.

Tested and working 110%

How did you do it? I could not get it up to date from 16 april tot 22 may

rpistutters · May 25, 2020 at 2:19 PM

Huge thanks HiassofT

That's working brilliantly.

cat2115 · May 25, 2020 at 4:07 PM

HiassofT

1) Just curious, whenever LibreElec dev push new update for Kodi 18.7, the code you mention no longer needed?

~~Now, I'm on 9.2.2 so I don't feel like downgrading. Is 9.2.2 work with the code you mentioned? I have RPi4 4gb~~

Tried on 9.2.2 and it works.

Quote

May 22 2020 21:12:25

Copyright (c) 2012 Broadcom

version 4da3e1264076308eda90652cb98b553ae0586390 (clean) (release) (start_x)

Thanks.

**HiassofT** · May 25, 2020 at 4:35 PM

Yes, 9.2.3 will contain the fixed firmware and the manual steps I posted are no longer needed.

The changes aren't in our repo yet, we are currently working on it.

so long,

Hias

Noise / artefacts when playing back 4K HEVC video on RPi4 + LE 9.2.1 (no problems on LE 9.2.0)

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