[FFmpeg-trac] #3631(undetermined:closed): Aspect ratio change in the middle of a video stream

[FFmpeg]

#3631: Aspect ratio change in the middle of a video stream
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             Reporter:  mar          |                    Owner:
                 Type:  defect       |                   Status:  closed
             Priority:  normal       |                Component:
              Version:  git-master   |  undetermined
             Keywords:  aspect       |               Resolution:
             Blocking:               |               Blocked By:
Analyzed by developer:  0            |  Reproduced by developer:  0
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Changes (by cehoyos):

 * status:  new => closed


Comment:

 Replying to [comment:7 mar]:
 > However, if I view the jpeg in another viewer (e.g. Firefox or Photoshop
 or the Windows default image viewer) it does not display correctly. And
 also the pixel size is not correct.

 So maybe you used the wrong bug tracker?

 > It seems that the information of the aspect ratio is preserved in the
 jpeg file and that ffplay "stretches" the image when it is displayed

 Note that this is exactly what is done for your input video.

 > (stretching also causes a bit of quality loss).

 The opposite is true afaict (the scaling filter necessary to produce
 output files with sar==1 is not lossless).

 > But the image is not "stretched" by other viewers. Is this saving of the
 aspect ratio in the jpeg a "proprietary" feature used by ffmpeg or are all
 those other vierwers "buggy"?

 It is definitely not "proprietary" but specified for jpeg.
 Please use {{{-vf scale=h=ih:w=sar*iw}}} to produce output files with
 sar==1.
 (Sorry if this is not the 100% exact filter command, in any case the scale
 filter is able to produce output files as you want them.)

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Ticket URL: <https://trac.ffmpeg.org/ticket/3631#comment:8>
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