[FFmpeg-trac] #5724(avfilter:new): customizable frame change detection

[FFmpeg]

#5724: customizable frame change detection
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             Reporter:  dha4t     |                     Type:  enhancement
               Status:  new       |                 Priority:  normal
            Component:  avfilter  |                  Version:  unspecified
             Keywords:            |               Blocked By:
             Blocking:            |  Reproduced by developer:  0
Analyzed by developer:  0         |
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 Proposed feature request for a frame change detection algorithm similar to
 "scene" but capable of comparing current frame to previously detected
 changed frame (or specified number of frames previous) rather than of
 consecutive frames in the video.  This feature might also accept a "zoom"
 parameter to analyze the frame more granularly to detect localized changes
 (i.e., lecture capture slide annotations). The zoom parameter would divide
 the frame into a "square" grid and analyze each section of the grid
 individually.  The algorithm could be passed the threshold value and
 return true once the threshold has been reached by any individual section,
 eliminating the need to further analyze the frame.

 Possible command line:

 ffmpeg -i input.mp4 -vf "select='frame_change(threshold, ref_frame,
 zoom)'" -vsync vfr thumbnail%03d.jpg

 Where:
 double threshold [required]
 0 = minimum change detected
 1 = maximum change detected

 int ref_frame [optional, default 0]
 0 = reference frame is previously detected changed frame
 1 = reference frame is 1 frame prior
 ...
 30 = reference frame is 30 frames prior (to detect fades/dissolves)

 int zoom [optional, default 1]
 divides the frame into a grid with x rows and x columns and analyzes
 sections individually

 I had high hopes of being able to do this myself but quickly learned I
 don't have the development skills necessary without really messing things
 up.

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Ticket URL: <https://trac.ffmpeg.org/ticket/5724>
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