[mythtv-users] commercial flagging

Chris Pinkham cpinkham at bc2va.org
Tue Dec 5 02:40:53 UTC 2006

* On Mon Dec 04, 2006 at 06:13:00PM -0800, Brad DerManouelian wrote:
> > it.  One thing I thought I'd suggest is that (here in the US, anyways)
> > pretty much every show starts with a "TV-13" or "TV-MA" or similar
> > symbol at the top-left (or maybe top-right) of the screen.  It appears
> > almost always at the beginning of the show, and sometimes after a
> > commercial break.  I suppose it would be possible for the flagger to
> > look for this symbol, since the sequence it appears in is almost
> > definitely *not* a commercial.
> You mean like the "logo detection" method that you can choose?

No, he means the rating symbol, exactly what he's describing.  I started
coding something to detect this one time, but never committed anything
to SVN.  Logo Detection should not pick this up since it only occurs
for a short period after commercial breaks, and not throughout most of
the video like a normal logo does.  In fact, in current SVN, you'll see
a call to CheckRatingSymbol() commented out because I never got it working
well enough to commit.  I haven't looked at that in years though, and
have some different ideas now, so it could be possible, but it's not
high on my priority list right now.  The rating symbols could be detected
using the same edge-detection logic that we use to detect a normal logo,
just that we would only expect the rating symbol to be around for a short
while after each commercial break.

> > Another thing I thought might be interesting to try would be to look
> > at the colors used to try and find commercials.  This would work
> > especially well for cartoons, where similar colors are used
> > throughout, and the commercials will have very different color
> > schemes.
> You mean like scene-change detection like you can choose?

No, doesn't sound like he's describing scene-change detection here.
Sounds like he's saying that since cartoons are in say 16 or 32 colors
and the commercials are in thousands, that that would be a good way to
detect commercials during cartoon shows.  I could see this being
effective for some cartoons and it wouldn't be all that hard to implement
since we already build a histogram for each frame in order to do the
scene-change detection.


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