[mythtv] Extending commflag to detect borked recordings

Tony Lill ajlill at ajlc.waterloo.on.ca
Tue Jun 19 17:37:21 UTC 2007

Last night I was watching a movie, and about an hour in, just when it
was getting interesting, I got to watch my cable box reset
itself. Verry annoying.

I got to thinking, how hard would it be for myth to detect that sort
of thing and do something intelligent. If you are recording off a
digital source, the most common errors are frozen frames or long blank

Now, commflag already does blank frame detection. In fact, it seems to
do it twice. In BlankFrameDetector, when contructing the break map, it
can check if the blank interval length is above some value, say 10
minutes, and return an error value indicateing the recording is
probably broken.

It looks like in the ClassicComDetector, It keeps a total blank frame
count. In fact, in ClassicCommDetector::CleanupFrameInfo, it uses it
to see if there are too few blank frames (to check for noisy signal.
It should be easy t add a check so that if that is above some
threshold, say 1/6 (10 min blank in a 60 minute show), we can declare
the recording broken.

Now, either mythcomflag can return a value that the jobqueue code
could interpret and do a delete with re-record, or the commflag
program could send a delete message to the backend.

What do y'all think of this?

Next question is, is there any code in the commflagger that does, or
can be used to detect long static stretches. Maybe the scene change
code could also detect when it doesn't change.

Finally, any ideas on how to detect static, say, when analog cable is
soooo bad it's unwatchable?
Tony Lill,                         Tony.Lill at AJLC.Waterloo.ON.CA
President, A. J. Lill Consultants        fax/data (519) 650 3571
539 Grand Valley Dr., Cambridge, Ont. N3H 2S2     (519) 241 2461
--------------- http://www.ajlc.waterloo.on.ca/ ----------------

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 system (just a hobby, won't be big and professional like gnu) for
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	- Linus Torvalds, August 1991

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