[FFmpeg-trac] #9787(ffmpeg:new): The movie filter fails to preserve SAR for png resource

[FFmpeg]

#9787: The movie filter fails to preserve SAR for png resource
-------------------------------------+-------------------------------------
             Reporter:  Arnon        |                    Owner:  (none)
                 Type:  defect       |                   Status:  new
             Priority:  minor        |                Component:  ffmpeg
              Version:               |               Resolution:
             Keywords:  movie        |               Blocked By:
  filter png sar                     |
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
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Comment (by Balling):

 Yes, indeed the file has (use exiftool)
 Pixels Per Unit X               : 12
 Pixels Per Unit Y               : 11

 which means that this file has not square pixels.
 http://www.libpng.org/pub/png/book/chapter11.html#png.ch11.div.8

 {{{
 The simplest and least correct approach is to ignore the chunk; most
 current viewers do this.
 The best approach is to resample the image, a procedure that amounts to
 converting the image to a continuous (or analog) representation and then
 overlaying the desired pixel grid on that.

 }}}

 Of course in pratice that is not what should be done when you convert
 between formats that all have this metadata. t.1+000001.png also has the
 same metadata, so all is good. In fact the video itself has


 {{{
 176x144 [SAR 12:11 DAR 4:3]

 }}}

 while your second command has
 {{{
 176x144 [SAR 1:1 DAR 11:9],

 }}}
-- 
Ticket URL: <https://trac.ffmpeg.org/ticket/9787#comment:2>
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