Short and zero length recording

[Nistrod]

I have four tuners. Last night they were all in use.
One of the recordings was zero length, and another very short (15 mins of a 1 hour show).
All shows had 1 min pre-padding and 15 mins post padding.
Times below are based on the file names.

Shows were:
QI 20:00-20:32 (ABC Frequency, tuner 20)
The Bridge 20:30-21:35 (SBS Freq, tuner 22) short
Living with the Amish 20:30-21:30 (SBS freq, tuner 22) zero length
Gruen Planet 20:32-21:08 (ABC Freq, tuner 21)
Good Wife 20:34-21:36 (Ch10 Freq, tuner 23)
Kitchen Cabinet 21:31-22:03 (ABC Freq, tuner 21)

As can be seen only three frequencies are in use, although all four tuners are used.
Both failing shows are on the one tuner, but it works fine with Live TV.
Postprocessing started at the expected time (i.e. 15 mins after show end), except for the zero length file.

Log is attached.
Any idea why things are short/missing?

[Graham]

The log shows only a single minute of events.

A wild guess would be a signal quality problem. The signal quality might drop, the tuner might stop sending data, the file might stop growing. When the signal quality comes back, the record process might not restart writing the file properly.

[Nistrod]

Oops, sorry, wrong log. New one attached.
Funny that it got a good signal for 15 mins on the short show, but nothing on the other one on the same tuner at the same time.

[johnsonx42]

I'd say Graham's guess was correct. It didn't get a signal lock on the SBS frequency using tuner 22:

Code:

2012-10-10 20:29:04.678    [DEBUG][7]    locked=0, present=1, strength=0, quality=10   (took 15ms to check)

every other recording in that log reported a good signal lock, with a better quality score.

[Nistrod]

OK, so locked=0 means no lock, and strength=0 doesn't sound good.
But I got 15 mins of one of the shows, and they both started at the same time. Strange.
It was a windy night, and maybe that tuner needs a stronger signal.
I will drop it to the bottom of the list.

Thanks

[Graham]

Back in the day, I was using a different aerial and the broadcasts were at lower strength. I would sometimes get strange symptoms. I (and the aerial installer guy) thought it was worse on windy days because there are trees close by that would move and interfere. I also got different results from different tuners. A fifteen foot pole helped!