Video stutters for a few seconds after changing channels

Channels Apple TV
#1

Hi all,

I haven't seen a post describing exactly the same problem I'm having:

Video stutters on most, but seemingly not all, channels about a minute after tuning the channel. The stutter recurs after a few minutes. The visual effect is heavy pixelation of the live video (audio seems unaffected) for a few seconds followed by a "fast forward" effect catching the video up, followed by normal video operation. This happens on live tv, and is baked into recordings on the DVR. I've watched the HD HomeRun's bitrate while this is happening and it drops to <1.0 mbps while stuttering, then shoots up to >20 mbps during the fast forward, ultimately normalizing to around 9 mbps. On some channels this behavior recurs every few minutes, on some it’s a one time thing. This behavior occurs regardless of whether the computer that serves as a DVR is on or not.

I’m running Channels on two different 4K Apple TVs, one is wired directly to a switch, and the other is wireless. The issue happens on both. The switch is a unifi US-16-150W which is connected to an overpowered pfsense box dedicated to routing.

I’m wondering if there’s a cablecard issue or a problem with the HD HomeRun itself. Any thoughts on how to resolve this problem would be hugely appreciated.

Thank you in advance for any suggestions.

#2

Are the HDHR and DVR both hardwired into the same switch? Do you have tuner sharing enabled on the Apple TV app?

#3

This indicates packet drops over the network, and explains why the recordings have glitches as well. I would double check the network path between the HDHR and DVR, and try to minimize hops as much as possible

#4

Yes and yes. The issue predates the switch though. I changed it out recently in the hopes that a higher powered piece of kit would resolve the issue. No joy though.

#5

The HDHR and the DVR are plugged into the same switch, all through CAT 6, and physically located close together. Is there a better way to route them? Could there be a hardware issue? I've upgraded my switch with no improvement in performance, but I'm willing to try anything.

#6

I should also mention that it's a comparatively new problem. I've had this same install with no differences for nearly a year and it's only in the last couple of months that the stuttering / fast-forward issue has presented itself. The original hardware (a relatively inexpensive netgear switch) was was working perfectly. The only change I've made to anything (aside from the switch upgrade) was to replace the HDD in my DVR (a ThinkCentre TS140) with a SDD. The DVR drive remained unchanged though.

#7

If true, then the app would be communicating directly to the HDHR.

Does it happen with tuner sharing off (a per client setting)?

Do you see the issue using any other app (HDHR/VLC/ChannelsDVRwebui/etc)?

Have you tried replacing the network cable to the HDHR or the power supply on the HDHR?

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#8

You could also try a network packet loss test on your HDHR following SD's FAQ article.

Low level test for network packet loss - CONNECT/EXTEND/PRIME/EXPAND:
https://forum.silicondust.com/forum/viewtopic.php?f=15&p=62283
From a cmd prompt run:
hdhomerun_config FFFFFFFF set /tuner0/vchannel 706
hdhomerun_config FFFFFFFF save /tuner0 null
..............................................................

CTRL-C to stop

-- Video statistics --
60430 packets received, 0 overflow errors, 0 network errors, 0 transport errors, 0 sequence errors

Release the tuner
hdhomerun_config FFFFFFFF set /tuner0/vchannel none

Replace vchannel 706 with the channel number for an unprotected channel in your area.
If you have more than one HDHomeRun unit then replace "FFFFFFFF" with the device ID of the desired unit.
You should see a series of dots. "n" indicates network packet loss. "t" indicates a reception error. "s" is informational. While saving the stream, a single period . will be displayed every second. Additionally, as of the 20080609 release, the hdhomerun_config will detect reception and network errors, replacing the. with an alternative character to indicate the problem.
Example output:
............n...............................n..........ts..........
-- Video statistics --
46998 packets received, 0 overflow errors, 2 network errors, 1 transport errors, 1 sequence errors

Show ethernet speed and duplex
hdhomerun_config FFFFFFFF get /sys/debug
mem: nbm=611195/13649 npf=81896 dmf=1213167
loop: pkt=0
t0: pt=11 cal=-541
t1: pt=11 cal=-539
t2: pt=11 cal=-543
eth: link=1000f <-- 1 gbps/full-duplex

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