Periodic pixellation happens during playback (Windows DVR + Flow Control)

Channels Apple TV
#1

Hi there - I’m using DVR 2017.10.24.2330 and Apple TV’s DVR app version 3.1 (on tvOS 11) w/ HDHR prime and things are generally great. Both are connected over gigabit ethernet, and my HDHR prime’s signal strength is usually in the 95%+ range.

On a variety of occasions though (over the past month or so across various DVR/Apple TV versions), playback will play and then periodically gets pixellated/garbled for a few seconds every 5-15 minutes. It’s incredibly annoying and frustrating, and it happens at least once a day while watching live or recorded shows. And when I watch the original source video file on my Windows PC (where the DVR server runs), they play back just fine.

Can someone help look into this? I can share files on google drive, etc to help troubleshoot.

#2

Just saw this thread/post below… I haven’t tried tvOS 11.1, but are folks convinced that that’s the resolution for this? I’d prefer not to install the 11.1 beta, but then again this pixellation is getting pretty bad…

#3

When it happens on a recording, does rewinding and replaying make it happen again at the same spot?

#4

I tried to reproduce it this morning and after watching 15 minutes of the same video that had issues last night, there was no pixellation. I’ll try watching other recordings later to see if there’s an issue, but this seems to support the CPU performance concern which hopefully is fixed in iOS 11.1 (vs. a concern with the video file itself)

#5

The tvOS 11.0 bug causes very slight hiccups lasting less than a second.

The pixelation you’re describing sounds like a different issue, one that’s usually related to the network connection.

The Apple TV 4 only has a 100mbps Ethernet port, so maybe you can try Wi-Fi instead to see if it’s any better.

Do you have the tuner sharing option enabled in the app?

#6

I just checked and the tuner sharing option in the app is off (I have never touched that setting). Also, my network is typically rock solid, so I don’t think that would be an issue. I’ll circle back if this is still an issue after 11.1.

#7

If the recordings are fine on disk, yet pixelated by the time they reach your ATV, then something must be happening to them while they go over the network.

The known issue on tvOS 11.0 causes frame-dropping, where 1-2 frames are missed every so often causing the picture to “jump ahead” or “hiccup”. It is barely noticeable and lasts a fraction of a second. What you’re seeing does not sound like the same problem.

#8

I stand corrected. It turns out the original video files do indeed have pixellation on my windows dvr server (I must have viewed a wrong episode initially). So it looks like it’s not an Apple TV issue at all. I guess I’ll bring this up with silicon dust to see if they have any suggestions.

#9

Please check your windows machine to make sure Flow Control is off on the Ethernet driver

#10

I just checked and flow control was enabled, so I just disabled it. Will keep our eye out to see if that fixes it going forward. Thanks! (And if so, could be a good tip to add to an faq/etc ifnone exists for future users)

#11

Thanks, let me know.

I’m hoping to make some improvements to the windows installer soon to make this part of it. It’s only required if you use an ATV4 over Ethernet (since that model only has a 100mbps port)

#12

Can you please explain how flow control might allow for occasional pixelation, and for that matter what flow control is?

#13

Here’s some more details on Flow Control and why it’s bad: https://www.smallnetbuilder.com/lanwan/lanwan-features/30212-when-flow-control-is-not-a-good-thing

TCP is an advanced protocol with its own flow control mechanisms. Ethernet Flow Control is much older, and very crude. It broadcasts a PAUSE command which tells everything on your network to stop sending data.

#14

Thank you.

#15

Would disabling flow control be only recommended on a server PC or would it be beneficial for all client PCs in a personal network as well?

#16

The server should be enough. The issue only affects the ATV4 since it has a 100mbps port. Here are the exact steps that cause recording corruption:

  1. DVR is running on Windows with Ethernet Flow Control = On
  • DVR is recording something
  • ATV4 is connected to network via 100mbps Ethernet
  • ATV4 stats watching any recording from the DVR
  • ATV4 uses skip or scrub features to switch to a different part of the file

Seeking around a large mpeg2 file maxes out the network connection between the ATV4 and the DVR (since its only 100mbps, i.e. 12MB/s). Once the connection is maxed out, the Windows machine will send out a PAUSE frame to the entire network. The HDHR receives this PAUSE frame and stops sending video data. Thus the recording in progress is now pixelated and missing audio/video.

FYI, with the latest version of the DVR you can now right click on the system tray icon and click "Fix Ethernet Settings" to disable Flow Control. The option only appears if Flow Control is enabled.

#17

Much Thanks.

#18

Quick update that I’ve had flow control disabled for about a week now and it’s been rock solid, no pixelation whatsoever. Thanks again for the help with this!

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