[mythtv-users] Detecting all-black videos

[Richard Freeman]

As has been discussed a few times on this list, I have a DirecTV 
receiver that occasionally outputs only black screen with no 
video/sound.  When this happens the tuner appears to work normally from 
the serial interface as far as I can tell, but it outputs only black.

My question is whether it is possible to detect these all-black no-sound 
videos from a script of some sort.  I'd like to set up some kind of cron 
job or maybe a user job that detects these videos and sends out some 
kind of alert when the receiver is in this state so that the damage is 
minimized (I've sometimes discovered the problem after several days of 
recordings are all blank).

Can anybody think of suitable tools.  A command-line tool that could 
measure the average brightness of a range of frames or the average 
volume of a given time range would be perfect.  I'm sure I could figure 
out the rest...

Alternatively - if anybody has figured out a way to detect this problem 
via the serial interface I'll just add the check to a cron job or my 
channel changing script and catch it there.  That would probably be a 
much cleaner solution.  And if anybody has a way to reset a DirecTV 
receiver short of having a controllable power switch on it let me know!