[FFmpeg-trac] #2559(avfilter:new): Bad pixel format negociation with scale and gray

[FFmpeg]

#2559: Bad pixel format negociation with scale and gray
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             Reporter:  ubitux      |                    Owner:
                 Type:  defect      |                   Status:  new
             Priority:  normal      |                Component:  avfilter
              Version:  git-master  |               Resolution:
             Keywords:              |               Blocked By:
             Blocking:              |  Reproduced by developer:  0
Analyzed by developer:  0           |
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Comment (by ubitux):

 Replying to [comment:4 Cigaes]:
 > cehoyos is right, the behaviour is normal.
 >
 > The auto-inserted filters are on the pad-overlay and edgedetect-overlay
 links, they are completely unrelated to the problem at hand, which happens
 on the input side of edgedetect.
 >
 > Note that you can get the same result without inserting the scale
 filter: just move the edgedetect definition before the split filter.
 >
 > I do not think that "solving" this kind of problem is a practical
 solution. At some point, users need to realize that complex filter graph
 sometimes need explicit format specification.

 While this behaviour might be "normal" with the current design, I don't
 understand how that can be the expected one.

 How can a user know if he needs explicit format specification or no
 (except by observing random craziness in some cases)?

 ...and I still believe the "lossless" path should be prefered over the
 "optimized" one. Inserting a gray auto-scaler in this place "sometimes" is
 IMO a non-sense from a user experience PoV.

 So while this might not be considered a bug in itself, it can be stated as
 a design problem or current limitation nevertheless. Feel free to reword
 and re-qualify the ticket.

-- 
Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/2559#comment:5>
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