[mythtv] rolling up my sleeves: a few questions about commflagging

Brian J. Murrell brian at interlinx.bc.ca
Sun Jan 26 13:41:38 UTC 2014

Ah ha!

So, I found the place where commercials breaks are calculated from the
blank frame map and using some badly flagged material found something
very interesting.  But maybe somebody here has already realized this.

The problem is with streams that switch the FPS during some commercials
in the stream.  Since I am in NTSC-land, this could mean a switch from
the initial FPS of the stream of 29.97 to 24 fps for _some_ commercials.

Since the code in ClassicCommDetector::BuildBlankFrameCommList() assumes
that the fps is constant for the whole stream, it gets confused when a
30 second (at 24fps) commercial break is calculated at 24 seconds.

So really, ClassicCommDetector::BuildBlankFrameCommList() needs to stop
assuming a constant fps and roll with the change as it happens in the

And in fact, this change in fps can actually be used to help indicate

I will see if I can figure out a way to implement that.

As I do, I am open to ideas on the correct approach if anyone cares to
provide some guidance.


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