[mythtv-users] HDHomeRun tuners and network switches

[Dave Ulrick]

On 1/20/22 7:51 AM, James Abernathy wrote:
> I'm trying to fix some issues with mythtv having breakups in the 
> signal that could be a number of things like antenna placement, 
> original signal quality, or networking issues.
>
> My production mythtv backend is using a WinTV quadHD PCI3 tuner card 
> and I generally don't have issues with those recordings.  It's always 
> the HDHomerun tuners that are connected to a test backend.
>
> I watch either backend using FireTV 4K sticks or Nvidia Shield TV with 
> the mythfrontend and Leanfront apps. So lots of networking potential 
> problem areas.  All of the streaming devices and backends are wired 
> with either CAT5e or CAT 6 cables.
>
> I have at the top of the tree a TP Link AX50 WiFi 6 AP/router.  Each 
> of the ports are connected to 8-port GbE switches in other cabinets or 
> rooms.
>
> The problem got bad enough this morning that I decided to dig deeper 
> into the situation.  While watching the recorded morning news, the 
> picture kept pixelating with lost sound a lot more than is tolerable.  
> I checked the HDHR tuner with their signal app and the quality and 
> stability of the signal looked great.
>
> The Shield TV and mythtv test backend that was recording the program 
> are on the same switch 1 in a cabinet and the HDHR tuner was connected 
> to another switch in another cabinet.  So I moved the cables around so 
> that one of the GbE switches had the HDHR, mythtv backend, and the 
> cable running to the cabinet with a switch for the streaming devices. 
> This seems to fix the issue.  However if the cable going to the 
> streaming devices is plugged into the switch above then I have issues. 
> An attempt at a schematic below to make it clearer.
>
> AP-router-----> switch 1 in closet (test mythtv-backend, HDHR tuner)
>                |-----> switch 2 in closet
>                |-----> switch 3 in cabinet with streaming devices 
> (FireTV, Shield)
>
> The above has the most break ups when watching
>
> However, moving the cable leading to switch 3 from the AP/router to 
> switch 1 seems to work best.
>
> Does this make sense or point to a problem?
>

Maybe the pixelization is caused by a network issue.

A problem that moves around when network cables are rearranged might be 
caused by a marginal CatX cable or a bad switch port.

I've experienced two scenarios with CatX cables: (1) the switch ports 
connected to the cable negotiated to 100 Mbps or 10 Mbps instead of the 
expected 1 Gbps or (2) the switch ports negotiated to 1 Gbps but a high 
error rate was caused by an inadequate cable (e.g., a long Cat5 cable), 
an incorrectly terminated cable, or interference. If the cable is a path 
to/from another switch, either scenario can have the effect of limiting 
the network bandwidth that's handled by one of the switches. If you have 
spare Cat5e or Cat6 cables on hand, see if the issue goes away when you 
replace a cable.

Regarding interference, make sure that your CatX cables aren't too close 
to AC in-wall wiring, AC power cables, or interference-generating 
appliances such as fluorescent lights. Lengthy CatX cable runs that are 
parallel to nearby AC wiring can be a particular problem. If you have a 
very long Cat5x cable, consider replacing it with Cat6 which is designed 
to be less sensitive to interference compared with Cat5x. If you 
discover an interference issue that won't go away, consider shielded 
Cat6 cables but they will be effective only if all Ethernet jacks on the 
path are grounded (i.e., a metallic tab is present on the two sides of 
the switch port).

To check out a possible switch port issue, try moving each end of the 
cable to another port on the same switch. Do this one end at a time. 
Note that it's not super-difficult for an incorrectly inserted cable 
terminator (plug) to damage the tiny little wires at the bottom of the 
switch port.

Dave