[FFmpeg-trac] #9757(avfilter:new): cropdetect ignores a value of 1 as the round parameter

[FFmpeg]

#9757: cropdetect ignores a value of 1 as the round parameter
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             Reporter:  Llyw         |                    Owner:  (none)
                 Type:  enhancement  |                   Status:  new
             Priority:  normal       |                Component:  avfilter
              Version:  unspecified  |               Resolution:
             Keywords:  cropdetect   |               Blocked By:
  round                              |
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
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Comment (by Llyw):

 I just took a look at the source code and realized that there are even
 more restrictions in place that are not documented: In addition to the
 `round` parameter needing to be greater than 1, it will also automatically
 get multiplied by 2 if the input value is odd and the offsets for the crop
 rectangle are also modified such that they are divisible by 2.

 While a comment in the code suggests that this has something to do with
 the YUV color model, the code more likely was added to ensure that one
 will obtain an output that works with chroma subsampled video.

 However, again, such requirements would not have to be met in my use case
 (or when you are working with non-subsampled formats) and you can already
 tell the `crop` filter that you want it to be exact. But instead of a
 simple relaxation of the minimum value for `round`, it seems that I would
 need you to introduce a setting that would drop the aforementioned
 restrictions of the `round` parameter and modification of `cropdetect`'s
 output altogether, just like `exact=1` does for `crop`. Such a setting
 could be off by default to keep things backwards portable.
-- 
Ticket URL: <https://trac.ffmpeg.org/ticket/9757#comment:6>
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