Can't get rid of pixelation that suddenly appeared on multiple tuners

Reception, channel detection, network issues, CableCARD setup, etc.
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googalus.maximus
Posts: 6
Joined: Mon Jan 09, 2017 5:19 pm

Can't get rid of pixelation that suddenly appeared on multiple tuners

Post by googalus.maximus »

I have a pixelation issue on several stations and I can't figure out how to get rid of it.

I have a MythTv system set up with two HDHR4-US tuners and I have an attic-mounted directional antenna with an inline amplifier. There are a half-dozen broadcast antennas located about 15 miles away (LOS) in, roughly, a cluster. I have many tall trees around my house.

I had been running an HDHR3 and an HDHR4 with very high quality, crystal clear reception on about 40 channels. I noticed that the HDHR4 could get additional channels from the "next over" metropolitan areas (Detroit, MI and Windsor, OT.) but I couldn't pull those channels in with the HDHR3 so I decided to replace the HDHR3 with an HDHR4 so I'd have a matched set.

Once I replaced the tuner, both tuners were still showing very high quality reception, but now about half of the channels seem to be experiencing random pixelation. All the bars in the SiliconDust config. utility app. show Signal Strength, Signal Quality, and Symbol Quality are all around 100% Some channels are like 98%, 95%, etc. but still really strong. I have one group of channels that show 80% Signal Quality, but it seems real strong still.

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I've re-tightend all the coax connections, re-pointed the antenna precisely, and tried taking the amplifier out of service. No improvement at all. I might watch TV for three hours without any problem, then suddenly can't even make out the picture due to pixelation problems, then it will clear up after a few minutes and be good again for hours...maybe. Maybe not.

I can't figure out what's causing this pixelation problem on some of my strongest channels and why it came on so suddenly when I changed out one of my HDHR tuners. There was no real problem before that and I can't see anything amiss that would be causing it now.

Any ideas?

googalus.maximus
Posts: 6
Joined: Mon Jan 09, 2017 5:19 pm

Re: Can't get rid of pixelation that suddenly appeared on multiple tuners

Post by googalus.maximus »

I tried an expiriment....

Clicking on the "View" button of the HDHR config utility and viewing the live stream thru VLC showed considerable pixelation.

While that was going on I also downloaded the same content stream concurently from the tuner and wrote the file to disk using wget. That version of the same content did not have pixelation problems.

Both were using the same tuner instance, both were using the same network connections, one was pixelated the other was not.

googalus.maximus
Posts: 6
Joined: Mon Jan 09, 2017 5:19 pm

Re: Can't get rid of pixelation that suddenly appeared on multiple tuners

Post by googalus.maximus »

I also generated log files: 104E971C and 10432894

If anyone there could take a look at them and tell me what they see...or forward them back to me so I can see them...I'd appreciate it.

markfromBrooklyn
Posts: 36
Joined: Tue Jul 14, 2015 2:36 am

Re: Can't get rid of pixelation that suddenly appeared on multiple tuners

Post by markfromBrooklyn »

You may want to turn on “send diagnostic information” if you have not already done so in the set up.

googalus.maximus
Posts: 6
Joined: Mon Jan 09, 2017 5:19 pm

Re: Can't get rid of pixelation that suddenly appeared on multiple tuners

Post by googalus.maximus »

markfromBrooklyn wrote:
Tue Sep 01, 2020 8:01 am
You may want to turn on “send diagnostic information” if you have not already done so in the set up.
I did. These are the unit serial numbers: 104E971C and 10432894.
Would be nice to have these logs to see for myself.

jasonl
Expert
Posts: 15303
Joined: Sun Oct 28, 2007 9:23 pm

Re: Can't get rid of pixelation that suddenly appeared on multiple tuners

Post by jasonl »


googalus.maximus
Posts: 6
Joined: Mon Jan 09, 2017 5:19 pm

Re: Can't get rid of pixelation that suddenly appeared on multiple tuners

Post by googalus.maximus »

jasonl wrote:
Wed Sep 02, 2020 7:04 pm
Run a network packet loss test, https://info.hdhomerun.com/info/trouble ... acket_loss.
Thanks. Didn't occur to me that it might not be the antenna/reception since it was affecting both tuners and only some stations.


Tried it a few times...

First try:

Code: Select all

nnn..tn..............................nt.........................n...........nnnnnnnnnnnnnnn...nnnnnnnnnnnnnnnnnnnn.......n.nn.n..nnnn......nnnnnnnnnnn.nn.nnnnnnnnnnnnnnnnn......n.n.......n............n..nnnnnnn.n....
-- Video statistics --
244956 packets received, 0 overflow errors, 1304 network errors, 117 transport errors, 1 sequence errors
Second:

Code: Select all

................................................................................................................................................................................................................n.........
-- Video statistics --
246050 packets received, 0 overflow errors, 1 network errors, 0 transport errors, 0 sequence errors
Third:

Code: Select all

nnnn........nnnnnnnnnn.................nn.nnnnnnnnnnnnnnnnnnnn.nnnnnnnnnnnnnn...........n.........n................................n.....n.....nn.nnnnnnnnnnnn..nn.................n..........n......nnn......nnnnnn..nnnnnn..........nnnnnnnnnnnnnnn.nnnn.n.nnnnnn..^C
-- Video statistics --
279715 packets received, 0 overflow errors, 1018 network errors, 0 transport errors, 0 sequence errors

googalus.maximus
Posts: 6
Joined: Mon Jan 09, 2017 5:19 pm

Re: Can't get rid of pixelation that suddenly appeared on multiple tuners

Post by googalus.maximus »

Quick follow up:
I "rebooted" my network. It seemed to help the packet loss issue considerably. The TV picture is not, as far as I can tell, improved.

The coax lead from my antenna to the dist. amp is a flimsy, thin, frail-looking kind of thing that came with the antenna... I've purchased a quad-shielded cable for that run and also a 4G filter (can't hurt for $16, right?) I'll try both of those and see what, if anything, that does toward the solution.

jasonl
Expert
Posts: 15303
Joined: Sun Oct 28, 2007 9:23 pm

Re: Can't get rid of pixelation that suddenly appeared on multiple tuners

Post by jasonl »

All those n's are network packet loss, so replacing the coax cable won't help there. You can either try to fix the packet loss by tweaking your sysctl settings (most likely net.core.rmem_max and net.ipv4.udp_rmem_min) or, better yet, switch to mythhdhrrecorder, which uses HTTP to stream from the HDHomeRun instead of UDP, and that works around minor packet loss issues by allowing the device to retransmit small amounts of lost data, which looks like what you're seeing (~0.5% loss).

https://github.com/garybuhrmaster/mythhdhrrecorder
https://www.mythtv.org/wiki/Mythhdhrrecorder

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