Troubleshooting a transcode issue: understanding output from hdhomerun_config debug

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ZeeJM
Posts: 1
Joined: Wed Nov 29, 2017 3:12 pm

Troubleshooting a transcode issue: understanding output from hdhomerun_config debug

Postby ZeeJM » Thu Jan 11, 2018 10:26 am

I'm using/accessing an Extend (HDTC-2US-M; firmware version 20171208) over gigabit ethernet and 802.11AC WiFi and I'm experiencing jitter and lost frames when using any of the transcode profiles. I should note I do not experience errors when transcoding is turned off.

The poor transcoding performance is not limited to a particular client platform; I've tested using the HDHomerun "Green" app, Kodi (HDhomerun PVR plug-in and NextPVR plug-in), VLC, and Plex on several different platforms/devices (Android phone; Fire TV (stick and box), and Windows 10 PCs).

As part of my troubleshooting process I've performed testing using the hdhomerun_config set/save process with no errors reported. I've also used hdhomerun_config get /tuner0/debug while streaming to a Windows 10 client over ethernet with transcoding both on and off.

Running a 2 hour test with transcoding off yields the following results:

C:\WINDOWS\system32>"C:\Program Files\Silicondust\HDHomeRun\hdhomerun_config" FFFFFFFF get /tuner0/debug
tun: ch=8vsb:599000000 lock=8vsb:599000000 ss=100 snq=81 seq=100 dbg=-2850/-9090
dev: bps=19818208 resync=0 overflow=0
ts: bps=16360512 te=0 crc=0
net: pps=1554 err=0 stop=0

A similar test with transcoding on (Mobile profile) yields the following:

C:\WINDOWS\system32>"C:\Program Files\Silicondust\HDHomeRun\hdhomerun_config" FFFFFFFF get /tuner0/debug
tun: ch=8vsb:599000000 lock=8vsb:599000000 ss=100 snq=81 seq=100 dbg=-2875/-8527
dev: bps=19481312 resync=0 overflow=0
ts: bps=4793248 te=0 crc=0
net: pps=470 err=2717 stop=0

In the first test scenario (no transcoding) the "net: err" counter is 0, while in the second scenario (transcoding on) the "net: err" counter shows 2717.

In reviewing the HDHomerun Development Guide (https://www.silicondust.com/hdhomerun/h ... opment.pdf), the "net: err" counter is described as "packets or TS frames dropped before transmission".

So, my test results have led me to the following questions:

Question #1: Can anybody point me to more detailed information regarding the "net: err" counter and its impact on video quality?
Question #2: Why would packet or frame loss increase when transcoding is on?

Any insight/ideas/feedback/suggestions are welcome.

jasonl
Silicondust
Posts: 11228
Joined: Sun Oct 28, 2007 9:23 pm

Re: Troubleshooting a transcode issue: understanding output from hdhomerun_config debug

Postby jasonl » Thu Jan 11, 2018 12:45 pm

When streaming via HTTP, net err indicates that the receiving end is not acknowledging the received data in a timely fashion, which can be due to network packet loss or delays in processing on the receiving end. When using UDP streaming, including the hdhomerun_config save command, there is no attempt to ensure delivery (no acknowledgements, no attempts to retransmit), so the HDHomeRun just streams and doesn't care what happens on the other side.


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