What time is it? Or, starting recording on time with MythTV

In the past couple of weeks, I’ve noticed that the programs that I’m recording on MythTV are missing the first few seconds to a minute of programs on the major networks. At first, I thought that maybe this was due to a clock problem on the MythTV system, so I checked the NTP synchronization. Everything looked good there. ntpd had switched away from my ISP’s server, probably because it is only stratum 3, and the public servers in the NTP pool are stratum 2. However, the time received from all four NTP servers was within a 45 millisecond gap, so apparently, my time was good. (For extra assurance, I used ntpdate against one of the NIST servers, and it came back with an adjustment of less than two milliseconds.)

Next, I checked the MythTV system against my TiVo. They appeared to have nearly identical time. That’s not particularly surprising. Years ago when I was troubleshooting a problem, I noticed on a network trace that the first task a TiVo performs when connecting to the service is to do a time update with NTP.

However, I noticed that my VCR, which receives a time signal from PBS, was three minutes faster than MythTV and TiVo. I’m not sure how PBS sets its time signal, but it seems weird that it’s three minutes off of the official time.

I’m not sure what I’ll do now. The active approach is to set Myth to start recording every program a minute early, but I’d have to go and change the configuration of every recording manually (or figure out how they are stored in the database). The passive approach is to hope that this is a transient problem that will correct itself if I leave it alone.

Anybody else experiencing this problem? If so, what did you do about it?

One Response to “What time is it? Or, starting recording on time with MythTV”

  1. Russ says:

    Many of the broadcasters are now mucking with the start times of programs, apparently in an effort to disrupt DVR users. It is frustrating, but adding tuners seems to be the only work-around…

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