[FFmpeg-user] Scene detection

lovelove googol at wolke7.net
Wed Sep 7 10:00:55 CEST 2011

Mark Himsley, Dave Rice, Peter B. and Stefano Sabatini: Thank you all for
your replies and useful suggestions. Sorry for the delay, I got a bit
side-tracked, but here is my follow-up post in the scene change detection

Stefano Sabatini wrote:
> Scene-detection looks like a much requested feature, please file a
> feature request on the issue tracker. 

I have written ticket#442: http://ffmpeg.org/trac/ffmpeg/ticket/442 and also
included your ideas and links. Sorry I can't do more, my coding skills
aren't even enough for "hello world" greetings :-(

Stefano Sabatini wrote:
> On the technical side: this has been already discussed on
> ffmpeg-devel, an underkill solution may be as simple as tweaking the
> select filter and adopt a simple pixel-per-pixel average difference as
> metric.
I think this would work only with motionless scenes, but could fail on e.g.
a continuous shot of a crowded street. Or spinning elements (
http://www.wheeloffortuneinfo.com/WheelAnimated-White.gif ). But I think you
did address this issue later on:

Stefano Sabatini wrote:
> For images with moving objects that's not a proper solution, and you need
> motion estimation code, which is already integrated in libavcodec, so the
> ideal solution would be to refactor the ME code in libavcodec and move it
> to libavutil. By doing this you may also improve the code itself, and thus
> improve the codecs using it at the same time.

What about the -sc_threshold parameter in FFmpeg? Isn't this actually the
implementation of what we are talking here?

Peter B. wrote:
> For ideas/details about how to implement a scene-cut detection, I  
> would suggest looking at the code of shotdetect (Johan Mathe is really  
> nice, and the license is LGPL by the way).
> His approach is actually really simple and straightforward, and we've  
> now been using it in our long-term archive solution for quite a while  
> and could provide information based on hands-on experience about what  
> to expect from that straight-forwards algorithm.

good call! 
In ticket#442 I also listed a couple of other open source examples which can
possibly be re-used.

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