[mythtv-users] HDHomeRun tuners and network switches

[Mike Perkins]

On 20/01/2022 14:24, Peter Bennett wrote:
> 
> On 1/20/22 8:51 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?
>>
>> Jim A
>>
>>
> I had this problem a few years back with the HD Homerun Prime. Pixellation every minute or so. After 
> lots of messing around it turned out that if the signal from the HDHomerun Prime to the backend 
> traveled through the router, sometimes a UDP message was dropped. I forget the router brand. 
> Reconfiguring the network so that the signal only traveled through a switch solved it. It looks like 
> this does not happen in your case, maybe the switch between the hd homerun and the backend is the 
> problem.
> 
> I verified it with this test, from the manual for the hd homerun prime, see below. When the signal 
> passed through the router, occasional errors were reported in the dots. Without the router between 
> there were no errors.
> 
> *Saving a stream:**
> *
> The hdhomerun_config command can be used to automate the process of saving to the local
> filesystem:
> format: hdhomerun_config <id> save /tuner<n> <filename>
> eg:     hdhomerun_config FFFFFFFF save /tuner0 capture.ts
> 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 --
> 23323 packets recieved, 2 network errors, 1 transport errors, 1 sequence errors
> 
> *Advanced:* A filename of “null” indicates no file should be created, allowing the use of the save
> command as a diagnostic tool.
> 
While I do not use a TP-Link switch as my router, I do have a TP-Link dedicated AP on my network and 
all my switches are also TP-Link. They are reliable enough and, more importantly, affordable.

Firstly, all the switches work fine. None are new but all have done service for many years. Two are 
unmanaged and the rest are "easy" managed. No problems (so far) with power supplies.

However, one of them has the AP plugged into it and that does have quirks. Due to the fact it wants 
to talk to others of its kind, and maybe participate in a network such as one might find in an 
office block, hotel or factory, it sends out Level 2 queries all the time and I can find no way to 
stop them.

To stop it from flooding the whole network it has its own dedicated switch port and VLAN and is 
firewalled off except for valid packets.

I do not have experience with your specific switch/router but perhaps it is trying to do something 
similar. Those packets could easily cause the loss of some UDP traffic.

-- 

Mike Perkins