Tvheadend

Use IPTRAF to see network traffic statistics.

 IPTraf
l Statistics for eth0 qqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqq
x
x               Total      Total    Incoming   Incoming    Outgoing   Outgoing
x             Packets      Bytes     Packets      Bytes     Packets      Bytes
x Total:        96810    258766K       18381    1314690       78429    257451K
x IP:           96810    257398K       18381    1045446       78429    256353K
x TCP:          96539    257357K       18139    1005773       78400    256351K
x UDP:            257      41254         232      39369          25       1885
x ICMP:             6        168           2         56           4        112
x Other IP:         8        248           8        248           0          0
x Non-IP:           0          0           0          0           0          0
x
x
x Total rates:       1563,6 kbytes/sec       Broadcast packets:          107
x                     514,4 packets/sec      Broadcast bytes:          12492
x
x Incoming rates:       8,4 kbytes/sec
x                     128,0 packets/sec
x                                            IP checksum errors:           0
x Outgoing rates:    1555,3 kbytes/sec
x                     386,4 packets/sec
x
x
x
x Elapsed time:   0:02
x

definitely on this developer boards pps kill CPU

I attached IPTraf statistics for one SD (not HD) transmission to Kodi. I was connected to Raspberry Pi by Remote Desktop so it is also included in statistics. Why did you write that "packets per seconds" kills CPU? What is wrong?

Update:
I noticed that you had statistics in kbytes/sec not in kbits/sec, so I changed mine to kbytes/sec in iptraf configuration. I made the same test for two HD transmissions to Kodi.

PPS * users = slow CPU response = high IRQ = high temp = low voltage
something with is painful for performance.

If MTU is so important, then maybe Odroid XU4Q ?

On Odroid XU4Q the MTU can be increased to 6975 [1] and it costs only $46. I can connect 4 DVB-T tuners to one USB 3.0 port via a USB hub like this: http://www.vakomtek.com/EN-H213/products/59/tc-242uk.html and then I can insert the whole into the enclosure as shown in the picture in the first post.

Odroid XU4Q has Ethernet and power ports on the opposite side than USB 3.0 ports. So, I will not need to use cables to connect Ethernet and power ports to the enclosure. In addition, there will be access to the micro SD and HDMI port from the outside of the enclosure in case of any problems.

Does anyone have a better idea for a low powered, small, quiet and cheap computer with several DVB-T tuners enclosed in one casing and able to serve about 10-20 clients?

PS. On Odroid C2 the MTU can not be changed: "The MTU size was limited by the S905 SoC hardware design." https://forum.odroid.com/viewtopic.php?t=28947

[1] https://books.google.pl/books?id=JbEXDgAAQBAJ&pg=PA14&lpg=PA14&dq=%22odroid+xu4%22+MTU&source=bl&ots=uJa1j5IZy9&sig=ACfU3U0CPiCZxcAV283apToBjI5ju77BOw&hl=pl&sa=X&ved=2ahUKEwipltW81ZPhAhVuk4sKHUKKD7AQ6AEwAnoECAgQAQ#v=onepage&q=%22odroid%20xu4%22%20MTU&f=false

MTU is totally different thing it is for packages over 1480 bites and fragmentation.
Your problem is packets per second "pps"

https://ownyourbits.com/2019/02/02/whats-wrong-with-the-raspberry-pi/

Very interesting, I've just spent a couple of days trying to get a August USB DVB-T210v2 device working with my Pi 3 and it was a complete disaster. What USB devices are you using out of interest. Are you using Raspian, which version of the kernel are you using. Also whats device are you using to split the signal 3 ways. I finally manage to get my Pi working with the Raspberry DVB hat and its working really well. Straight out of the box without having to install any media driver/modules, which saved a lot of time. Looks good, thanks for sharing.

I am using DVB-T tuners not DVB-T2. The hardware and installation is described on https://myserver.opentechnologies.pl/en/technical-documentation/
Additionally I installed Tvheadend 4.2.6 instead of 4.0.8 according to: https://tvheadend.org/projects/tvheadend/wiki/AptRepositories
So I changed:

sudo apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 379CE192D401AB61
echo 'deb http://dl.bintray.com/tvheadend/deb jessie release' | sudo tee -a /etc/apt/sources.list

sudo wget -qO- https://doozer.io/keys/tvheadend/tvheadend/pgp | sudo apt-key add -
echo 'deb https://dl.bintray.com/mpmc/deb raspbianjessie  stable-4.2' | sudo tee -a /etc/apt/sources.list

iw is wrote:

I am using DVB-T tuners not DVB-T2. The hardware and installation is described on https://myserver.opentechnologies.pl/en/technical-documentation/
Additionally I installed Tvheadend 4.2.6 instead of 4.0.8 according to: https://tvheadend.org/projects/tvheadend/wiki/AptRepositories
So I changed:
[...]to:
[...]

Small note, I would switch to the main repo, more info here now.