I have a bit of a complicated problem, so I try to explain it as clear as possible.
First, these are the hardware I will refer to later:
* Avermedia TD310 (dvb-c)
* Raspberry Pi 4 (this is the "TV", if I have not specified, I'm speaking about this)
Raspberry Pi OS
Tvheadend 4.3-2050~g52c3ed3ef (source built, but same with the Raspberry Pi OS package (4.3-1994~gc7b713edb))
Kodi 19.4 (Raspberry Pi OS package, popcornmix's gbm_matrix)
* Lenovo G550
Tvheadend 4.3-2050~g52c3ed3ef (AUR)
Kodi 19.4 (Arch package)
Nextpvr from docker image
* Desktop (i7 8700K, RTX2080)
Kodi 19.4 (Arch package)
* Win10 vm
AverTV (Official client software)
The whole hunting started about a week now, there was no problem before (or not that noticeable). The situation is that we have HD (1080i) channels that have around 10000-13000kbps bandwidth. There are no problems with them. But there are some HD channels that have only 6000-7000kpbs bandwidth, they are the problematic ones.
These channels are sometimes having artifacts when I'm watching them, like squares on the whole screen or part of it. Sometimes more, sometimes less frequent (between 3sec and 5min). But it does not happen every time. I have tested with a sports channel and the rule for it is it happens every time if it is a live broadcast, it sometimes happens if it is not a live broadcast, and there are times when no error happens.
When an error happens, the webui displays continuity errors and subscription errors. If I connect with multiple devices (Android, Linux) running Kodi every error looks exactly the same on every device and the error counters are incremented equally on the "Subscriptions" page.
Maybe related that I found an SD channel that throws 5 continuity errors/second every time, but no errors on the subscription or the screen.
What have I tried
* Running Tvheadend and Kodi on the Raspberry PI (this is what I described above). Errors are happened.
* Running Tvheadend on the G550 and watching from the Desktop. Errors are happened.
* Running Nextpvr on the G550 and watching from the Desktop. There is no error happened (at least not visible)
* Running AverTV on the Win10 vm and watching on it (AverTV says 97%-100% signal quality). There is no error happened (at least not visible)
Here is a video recorded by Tvheadend itself on the Raspberry Pi, but not all the artifacts are visible on it when I play it in VLC (Tvheadend says 9 Data Errors which is about right): https://drive.google.com/drive/folders/1QRuFCC-lYbch-JYs5dlHvsi4-nIpL4hU?usp=share_link
And here are some screen recordings which shows better the visuals of the issue: https://drive.google.com/drive/folders/17arPoE3G73Pg-14E9fb1ZR1BUS-Yty8r?usp=share_link
The attached log contains everything I can tick on the webui. It shows a local kodi subscripting to a channel, watching for a minute, and disconnecting. During the watching, about 10 errors happened.