Pixelation troubleshooting?

Reception, channel detection, network issues, CableCARD setup, etc.
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klaberte
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Joined: Sun Apr 27, 2008 11:27 am

Pixelation troubleshooting?

Post by klaberte » Fri Jul 26, 2019 10:12 am

I am seeing quite a bit of pixelation for certain recorded (and live) channels, in this case Xfinity Channel 376. (I note that I do not have that many channels in the 300 range, and this is the only one I record from in the 300's.) Is there a standard troubleshooting guide for this?

I use HDHomeRun Prime (Version 20190621) and a WD MyCloud NAS (20190621).

While watching live channel 376, here is what the tuner status reports:

============
Tuner 0 Status
Virtual Channel 376 MNBCHD
Frequency 79.000 MHz
Program Number 4
Authorization subscribed
CCI Protection unrestricted
Modulation Lock qam256
PCR Lock locked
Signal Strength 85% (-9.1 dBmV)
Signal Quality 91% (33.8 dB)
Symbol Quality 100%
Streaming Rate 3.780 Mbps
=============

Any help is most appreciated.

Mediaman
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Re: Pixelation troubleshooting?

Post by Mediaman » Sat Jul 27, 2019 4:37 pm

klaberte wrote:
Fri Jul 26, 2019 10:12 am
I am seeing quite a bit of pixelation for certain recorded (and live) channels, in this case Xfinity Channel 376. (I note that I do not have that many channels in the 300 range, and this is the only one I record from in the 300's.) Is there a standard troubleshooting guide for this?

I use HDHomeRun Prime (Version 20190621) and a WD MyCloud NAS (20190621).

While watching live channel 376, here is what the tuner status reports:

============
Tuner 0 Status
Virtual Channel 376 MNBCHD
Frequency 79.000 MHz
Program Number 4
Authorization subscribed
CCI Protection unrestricted
Modulation Lock qam256
PCR Lock locked
Signal Strength 85% (-9.1 dBmV)
Signal Quality 91% (33.8 dB)
Symbol Quality 100%
Streaming Rate 3.780 Mbps
=============

Any help is most appreciated.
The area in the forum for this is Hardware Setup, this is a link to the sticky thread in that section on setup and signal issues viewtopic.php?f=113&t=65715

Signal Strength is marginal, see thread for potential issues. Best remedy most likely is to reduce the number of splitters between tuner and the D-marc [where cable box is at on outside]. Tuners are more sensitive than routers/gateways.

jasonl
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Re: Pixelation troubleshooting?

Post by jasonl » Sun Jul 28, 2019 1:12 pm

Low-frequency channels like that are subject to interference from impulse noise, which is generated by things that convert electricity to motion (fans, motors, pumps, compressors, etc.) as well as fluorescent lights (especially cheap CFLs) and dimmer switches. For those who remember the analog TV days, this is the digital version of having the picture on the TV turn to fuzz when someone was using the vacuum cleaner nearby. Try to keep the HDHomeRun and any coax cables, amplifiers, and splitters as far away from such things as possible, and if there are any unused outlets or splitter ports, make sure they are properly terminated. Also make sure you're using good-quality RG6 coax cable to try to block out as much of it as possible. Anything you get from your cable provider should be fine, but if you went and bought cables from Walmart or something then compare them to proper cables from the provider and if they're any thinner or more flexible then they're suspect.

klaberte
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Joined: Sun Apr 27, 2008 11:27 am

Re: Pixelation troubleshooting?

Post by klaberte » Wed Aug 07, 2019 9:22 pm

OK, thanks, I see that my signal strength isn't fantastic. I can go through and check on splitters and un-terminated cables, and replace what seems to be sub-standard.

Are channels in the 200-300 more susceptible to noise than those in the low 1000's?

Is there any way to do diagnostic logging that might determine if my issues are elsewhere, e.g. lots of dropped packets from my NAS to my client?

signcarver
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Re: Pixelation troubleshooting?

Post by signcarver » Wed Aug 07, 2019 11:43 pm

The channel numbers you are mentioning are virtual... they don't tell you where they are and what type of interference the channel would most likely be susceptible to. In your case, 376 is on physical channel 5 (79 Mhz) but channel 375 or 377 may not even be close to that.

klaberte
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Joined: Sun Apr 27, 2008 11:27 am

Re: Pixelation troubleshooting?

Post by klaberte » Thu Aug 08, 2019 6:50 am

Good point. I now see the actual frequency in the tuner status. I note that many (most/all?) channels actual are listed twice in my channel lineup, e.g. Ch 376 and 1113 both map to 79 MHz. Any idea why they do this?

Also, is there any way to use the HDHomeRun status reports to learn more of the details of the video stream, e.g. specific codecs for audio and video, separate bit rate of audio, and the bit rate of the video?

NoReDist
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Re: Pixelation troubleshooting?

Post by NoReDist » Thu Aug 08, 2019 7:53 am

The dupe line-up entries are just a fancy thing Comcast is doing to re-organize the same line-up (and A/V streams) of channels, categorically, in the ch#s above 1000

Go to your line-up page and append: /lineup.json?show=tuning after the ip in the URL in your browser to see the codecs for each channel in your lineup. If you pull up the the HDHR_config_gui or view the webpage while streaming you can find a menu option that shows current bitrate - on your network -
If you want a real average bitrate over time or logged in some fashion, many 3rd party tools can expose, but the free version of TSReader is probably your best swiss army knife since you seem curious.

gtb
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Re: Pixelation troubleshooting?

Post by gtb » Thu Aug 08, 2019 9:33 am

NoReDist wrote:
Thu Aug 08, 2019 7:53 am
The dupe line-up entries are just a fancy thing Comcast is doing to re-organize the same line-up (and A/V streams) of channels, categorically, in the ch#s above 1000
It is called the MCLU (Master Channel LineUp), although I don't think that name ever made it to a public announcement when Comcast talked about creating the groupings and how it was going to be a great new thing for many(*). However, there are a few markets that had channel numbers above 1000 before the MLCU national rollout (sometimes because the predecessor company, before Comcast bought it, had them). That has made the migration and merging of the MCLU into the existing channels somewhat of a confusing mess for those markets.

Personally I just make all channels < 1000(**) disabled on my Prime and only have the MCLU numbers visible, but there are some who want to hold on to their old finger channel button muscle memory.


(*) These days in at least some advertisements Comcast is eschewing numbers and just suggesting you speak to your remote and say "Watch Game Of Thrones" and let the system figure out you mean HBO on channel 1802. As more and more people move to various on-demand streaming or previously recorded content there may end up being less and less linear TV to watch so the idea of a channel will be going away. As a person with a DVR (and that likely includes a lot of people on this forum), I don't care about channel nnnn, I only care about watching the show which I recorded at some previous time.

(**) In my market there are the music channels in the high 900's, but since I don't use my TV for music, I include them in the bulk disable.

klaberte
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Joined: Sun Apr 27, 2008 11:27 am

Re: Pixelation troubleshooting?

Post by klaberte » Sun Aug 11, 2019 8:04 pm

Quick follow up: I have found a substandard 4 way splitter in the circuit, when only a 1:2 splitter is necessary. I made that replacement and had a significant improvement in all my signal and symbol numbers. Far less pixelation. I also see a substandard cable in the critical path. Am ordering a solid RG6 cable to swap it. I'll let everyone know once my upgrades are done, but in this case, it seems that inferior cables and splitters are the problem.

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