How big of a buffer on a 4K movie does OSMC maintain

Hi guys. I have a Vero 4K. When playing 4k movies in isos I sometimes will get buffering at regular intervals. Its not always consistent. Sometimes the whole movie will play fine, sometimes it will go 20 second, 1 min, etc, and beffer. Changing chapters almost always triggers the problem and sometimes stopping and restarting with “Resume” will fix it. Sometimes not.

My question is, approximately, how much is it pulling on, say, an 4k Iso that is about 50GB encoded with HEVC/24k?

I have a synology nas behind a gigabit switch and 2 ethernet cables (link aggregation). Vero is connected to the same switch. I ran iperf on both as well as other devices. Everything seems be be correct, I get about close to the full 100Mb on the Vero, even when the video is showing the buffering problem.

When it does buffer, it does the 0 to 100% progress bar. This can sometimes be very slow - like 10+ seconds. Seems odd that it would be THAT slow.


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Short answer: it depends on how your shares are mounted

Sorry, meant to metion, it is NFS.

Are they mounted via fstab/autofs or mounted in Kodi?

Kodi. For example, in the sources.xml file I have:

        <path pathversion="1">nfs://</path>

I hadnt realized that would make a significant difference. Should I try fstab?

For NFS it may not, but it can’t hurt to try. I personally use autofs (there is no performance difference between autofs and fstab). WD Mycloud NAS -> 1G -> Router -> 100M -> V4K and have no buffering issues with my setup.

It will still make a difference, even with NFS.

Ok, interesting. I am reading your wiki now. Seems optimal to use NFS and autofs. If that is not the case, let me know.

I will give a shot. Thanks again.


autofs and fstab will have the same performance. The difference is that autofs handles network drops better. fstab can hang if the server reboots whereas autofs will handle that.

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So… “how big of a buffer on a 4K movie does OSMC maintain”?

The same as on any movie. The default setting on the Vero4K/+ is up to half a gig of memory.

Question. It sounds like the answers are towards the NFS cache/file cache on OS level. But if you have a file with a size of 4GB for example on the network, a 4 GB RAM device can’t buffer this file. Shouldn’t we be talking about Kodi’s internal memory cache for the buffering solution?

Kodi’s video cache is the solution. The issue seems to be why is it not getting topped up in a timely manner.

It’s just too much for 100Mbit. If the file is about 50 GB and has a 90 minute runtime that would average about 75Mbit, add a little bit of extra bandwidth for buffering, TCP overhead, stream protocol and some fancy DVD functions and who knows what and it’s ends up being too much.

To much for what? I regularly watch 4K movies with no buffering at all. I have an original Vero 4K with the 100M connection. All of my 4K content was ripped by me (using MakeMKV) with no processing other than removing unwanted audio tracks and subs.

@bmillham Are your rips 50GB or larger?
That’s getting near the theoretical max of the 100Mbit network. In that case your device needs 75Mbit every second to play the video. If Kodi plays the video and buffers the video ahead with a speed of 1x, that’s another 75Mbit. I think Kodi buffers a file with 4x or 5x with default settings, so something already has to give in there.
It explains why changing chapters is choppy (Kodi needs new data from network) and pausing and resuming (all bandwidth available for the buffer during video pause) helps it

The size of the file has nothing to do with it.

For example, if I have a 50G file that is a 30 minute clip, that’s going to use a large amount of bandwidth.
If I have a 50G file that is 3 hours long, it’s not going to use much bandwidth.

The video cache will not help much (if at all) for skipping chapters. Most likely when you skip to the next chapter it’s not in the cache so you will get a pause as it fills the cache again.

I personally don’t rate the kodi buffering.
On a 70Mbps etherline I can play 50Gbps files fine. I do sometimes notice less free ram % and I get buffering. Reload fixes it. I have Vero 4k+

Gentlemen, the topic starter used in his example 50Gb. I’m just pointing out that the bitRATE could be too high for a 100MBit device. (ps. the example of 50GB and 30 minutes can’t work on a 100Mbit in realtime playback)

@points The Vero 4k+ is a 1000MBit device so that limit is much higher.

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Hi all. This has been an very informative exchange, I appreciate the info.

An update from my end. I changed over to using autofs with a single mount to the root folder of the media files via nfs. MUCH better! I do see an occasional buffer after a chapter change but that is it. Nothing like the constant cycle I was seeing before. I will test some more but hopefully i am good from this point. Thanks @bmillham and @sam_nazarko.

The discussion about the megabit/gigabit is something I have wondered about. I have thought about upgrading to a 4k+ for the extra bandwidth, JIC. Is it really 75 mbps for a 4k movie? If so, does it actually pull across the network at that rate or is there some compression/decompression involved in the transfer?

Thanks again for all the help.