Bad video performance on Pi 3

Help and Support Raspberry Pi
21

You can and this is commonly done. Be aware it bypasses the polyfuse so if you accidentally short 5V/GND and your power supply doesn’t have a current limit you may cause some damage. Any decent power supply should have protection though.

22

Tried it with the original power supply (2.5A), still the same problem.

23

Did you try taking the switch out of the network link?

24

When i plug both directly into my router it works fine.

So the switch is the problem. But why? It seems to work fone, brings ~60-80 mB/s transfer rate to my laptop. Its a Cisco Linksys SE2800.

Any ideas?

25

Is your Cisco switch a managed switch ? (EG has a web interface or configuration utility) If so check to see if flow control is enabled on the ports. If not try enabling it.

Alternatively try adding smsc95xx.turbo_mode=Y to the end of the line in /boot/cmdline.txt then rebooting.

26

Switch is unmanaged. Will try changing the cmdline.txt tomorrow

27

Added the line, now everything seems works fine, even when Pi an server are plugged into the switch.

Can you help me to understand, what the line does and why it’s necessary? Why does it work on the router but not on the switch? Is smsc95xx the ethernet controller? Does the line force some kind of turbo mode? And if so, why isn’t the turbo mode always on? Do I have to edit the file again after updates? Should I try to delete the line again after an update, so that (if it works without the line) the system is more close to “out of the box” and (possibliy?) runs more stable?

Lots of questions…

Thanks at everyone so far for the help.

28

smsc95xx is the Ethernet controller yes. That option makes a couple of different changes - one is it increases the receive buffer size in the Ethernet driver, (by a lot) and another change I can’t recall off hand.

I had noticed that my Pi 2 had poor network performance on a switch with flow control disabled, but worked fine with flow control enabled.

@popcornmix suggested that option as a possible workaround and it did indeed seem to work for me - with it enabled I see no performance loss with flow control disabled. The interesting thing is that your unmanaged switch almost certainly has flow control enabled, and yet is still affected by this issue. (Maybe flow control does not work properly on that switch)

The “turbo” option is not enabled by default as it apparently can have detrimental effects under certain circumstances due to the large buffer allocations in the kernel.

There was some discussion about whether the buffer could be increased by a smaller amount and made the default, but that will require testing with some custom kernels with different buffer sizes to evaluate how safe it is and how big the buffer needs to be.

cc @popcornmix @sam_nazarko

We don’t touch cmdline.txt on upgrades so any customisations you make there will remain unless you did a complete fresh install.

29

If smsc95xx.turbo_mode=Y improves network playback, can you test with that option removed and smsc95xx.packetsize=4096 added instead?

We know turbo_mode causes issues in some heavy use cases (e.g. torrent downloading), so we’d like to find a safer alternative that still provides the network performance improvement.

You need to be on the April update for this option to be supported.

30

Unfortunately that doesn’t work. All Updates installed, but the old problem comes back. With turbo mode it is still working.

Edit: But it works slightly better than without any editing. The lags are approximately half as often as without the option.

I will stick with the turbo mode for now.

31

Could you try it with packetsize set to 8192 ?

32

Are these parameters available on Vero2 as well ? If so, where to put them ? I don’t see /boot/cmdline there.

33

This problem and therefore the solution is related to the Raspberry Pi.
If you have a problem with the Vero2 it must have a different reason. Suggest you open a new thread with respective logs attached.

34

Hi there!

  • I have the same issue: (running osmc on RPi 3 is faster than RPi-1, but when streaming the video often freezes)
  • I tried the solution: smsc95xx.turbo_mode=Y inside /boot/cmdline.txt

but the problem remains…

The fact is that my RPi-3 connects to my home’s router via the embedded wifi controller (but RPi-1 did the same with no problems), so…

is there any other settings that I should add inside /boot/cmdline.txt (or any other file) to solve this?

regards

35

You seem to be a little confused.

The turbo option is for the built in ethernet on a Pi - if you are using wifi it will not help you.

Secondly the Pi 1 does not have built in wifi, so your Pi 1’s wifi adaptor is obviously going to be different to the built in wifi of a Pi 3.

The first thing you need to do is to test your wifi speed, you should be able to find many threads that discuss how to do that.

36

You are right, I wrote this a bit fast… in the RPi-1 case a used a wifi adaptor with no problems…
So you suggest that the built-in wifi is the problem ?

I will search for issues on RPi-3 wifi speed, thanks anyway

37

Testing with an ethernet cable (even if you have to move the Pi closer to router to test) would be a useful test.
It that works fine you know it’s a wifi issue. If that fails then we can discount wifi and look elsewhere.

38

I will test it and report here …
thanks

39

I may be having the same problem - on ethernet, rpi3. Its on live TV only though - not sure whether that counts as the same, so I’ve started a new thread → Buffering issues on Pi3 ethernet tvheadend

My issue is also present on the device itself (i.e. from tvheadend to Kodi event without any network cable).

40

Hi again

  • ethernet
    I did some test connecting the ethernet cable into the RPi-3 and everything seemed to be ok. The use of the smsc95xx.turbo_mode=Y inside /boot/cmdline.txt file didn’t do much cause even without this, the stream was fine (actually I started testing with this setting and then without it. Now the RPi is ethernet streaming flawlessly even without this line).

  • wifi
    disconnecting the ethernet cable and enabling wifi, I found that the stream was flawless. Nothing compared with the first test. I cannot explain that!!
    I did nothing else (no change in any setting) but just test streaming via the ethernet first !!
    Now it’s being streaming video flawlessly via the wifi connection for the last three days.

I will post here if there will be any changes…
regards