[mythtv-users] Commercial detection and PVR-250?

[Jarrod K Gray]

Would it be worth pulling this information together to form a
Documentation section for the features of Myth? If someone were to come
along later and want to develop the commercial detection further, it might
be useful to have some reference material for that person to go by.

Jarrod

On Thu, 19 Jun 2003, Chris Pinkham wrote:

> More detailed descriptions can be found on the mailing list archives,
> but here's a quick description if you have blank frame with scene
> change detection turned on.
>
> Blank frame detection checks as many pixels as necessary to determine
> if a frame is blank.  It performs a grid search and stops looking if it
> encounters a bright pixel.
>
> Some calculations are then done on the blank frames to see which occur
> certain time distances apart (ie, 30, 45, 60, etc. seconds) to determine
> which look like commercials.  The "commercials" are then merged together
> into a commercial break list.
>
> The scene change detection looks at the Luminance histogram for each
> frame and determines if enough 'buckets' in the histogram differ by a
> certain percentage between the current frame and the previous.  If the
> difference is over a certain threshold, the code assumes the scene has
> changed.  This isn't a "scene" as in a play/movie, but things like the
> shot changing from one camera angle to another.
>
> The scene change marks are then looked at to see where high rates of
> scene change occur in the video since commercials have high rates of change.
>
> The code then checks over the commercial break list to see if any small
> holes (such as a 10-second spot at the beginning of a video and followed by
> a commercial) look like commercials.  If the hole has is flagged in the
> scene change table as having a high rate of scene changes then it's flagged as
> a commercial also.
>
> This is how the code works currently although it will probably be enhanced to
> do even better detection in the future (although it is very good for most
> things I watch even now).
>
> Chris
>
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