[mythtv-users] HDHomeRun tuners and network switches

Stephen Worthington stephen_agent at jsw.gen.nz
Fri Jan 21 10:52:34 UTC 2022


On Fri, 21 Jan 2022 05:23:32 -0500, you wrote:

>I appreciate the detailed explanation.  At present all my ports on my 
>home network are connected via switches and only one port on the router 
>has the top switch in the tree connected to it. So the problem should be 
>solved and certainly seems to.
>
>I am curious about the mention of dropped UDP packets being the 
>problem.  I thought MythTV v30 and beyond used the TCP method of dealing 
>with HDHR tuners so you could get the virtual channels, etc. Maybe I 
>don't understand that part of it.
>
>Jim A

I had not realised that MythTV now used TCP for recording from HDHRs.
Since TCP handles packet loss by retransmission of lost packets, you
would expect that it would not be bothered by an occasional lost
packet.  But even TCP can be overwhelmed by too many packet losses -
it slows down the transmission rate until the packet loss goes away.
So for a TCP connection to have a bad recording, the router throughput
for the bridged packets would need to be so low that the TCP
connection speed became lower than the speed of the channel being
recorded.  Which is entirely possible - routers really are very bad at
doing bridging.  However, if this was happening, you should see
disconnect/reconnect messages about losing the TCP connection and
having to restart it.  I would hope that sort of thing would always be
logged, as it is a fairly drastic problem that would cause loss of
quite a bit of a recording.


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