[PATCH] Re: [mythtv-users] How well does commercial detection

Risto Treksler risto at elkhornbanff.ca
Wed Apr 13 07:56:23 UTC 2005

On Tuesday 12 April 2005 10:41 pm, Chris Pinkham wrote:
> > So I am resending
> Got both of these actually.
sorry about the logjam
Thank you for commiting the patch

> >
> > 1) in strict mode - treat frames as blank only if logo is absent
> I get this part of the patch and see why it may reduce false positives
> where we detect show as commercial,
> but also see where it may cause 
> missing of the first and last commercials in a commercial break if the
> network displays their commercial through all blank frames before and
> after the commercial break.  Did you experience any of this after
> applying this change?

at least for me, the positives far outweigh the negatives

happened in two shows out of fifty that i have on the drive right now
but over all, even these shows detect better now than before.

a) far fewer false positives
b) it's consistent, and thus predictable
c) it's a minor problem 
   - it only misses a few seconds at the end of the comm block
     for only a couple of shows

> > 2) more fixes for the "long long" issue
> Thought these were OK since they were in a sprintf not an arg().  Were
> these generating warnings somewhere?

Remember this ?

2005-04-11 14:31:23.171 d : 102549 (00:04:00.56) (58)
2005-04-11 14:31:23.171 d : 107739 (00:05:00.59) (51)
for some reason, if it was "long long" it would display a "d" and insert a "0" 
into the argument list, causing a frame shift - making all debug output 

basically this makes debug output "work" for me

> > 3) fix for "white frames" triggering commercials
> So strict means black, non-strict means blank, correct?

more or less
-strict means "blank that is also reasonably dim"
-non-strict means "any blank"

> > 4) do not detect commercials less than 60 sec long, in the middle of a
> > show
> I had a question about this part, but after looking over the code 4-5
> times, I see what you're doing.  Seems to make sense.

I tested this quite a bit
- b4 this patch i was getting tons of 1 second breaks
- so this fixes this bug (of not honoring the min_comm_break_length)
- but still allows for short commercials in the beginning of the show

> I've seen commercial longer than the 00:05:35, but I think I may have
> calculated wrong when I set the max to 485, that's 00:08:05 which is a bit
> too long. :) Did you try any values in between 335 and 485 or did you pick

I have seen a few that are longer than 00:05:35 as well
heck i saw an 11 minute break the other day

It's just been my experience that
if a block of 6 minutes or longer was marked,
then quite often some of the actual show was being cut off.

> These look OK, I committed the patch to CVS, 

Thanks again

> and changed 
> MAX_COMM_BREAK_LENGTH down to 395 for now.  That's 00:06:35 so we can see
> how that goes.  I don't want to take it much lower before 0.18.

maybe make strict be 335 and non-strict be 395?
I'll try to test with 395 to see if it's better or worse

i was thinking about making this also an undocumented  setting in the 

maxCommBreakLength= gContext->GetNumSetting("MaxCommBreakLength",

Risto Treksler
Elkhorn Lodge
Banff, Alberta, Canada

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