[FFmpeg-trac] #706(avfilter:closed): scale filter doesn't understand »out_h«

FFmpeg trac at avcodec.org
Tue Dec 6 15:13:38 CET 2011

#706: scale filter doesn't understand »out_h«
             Reporter:  taeuber     |                    Owner:
                 Type:  defect      |                   Status:  closed
             Priority:  normal      |                Component:  avfilter
              Version:  git-master  |               Resolution:  fixed
             Keywords:  scale       |               Blocked By:
             Blocking:              |  Reproduced by developer:  1
Analyzed by developer:  1           |
Changes (by saste):

 * status:  new => closed
 * resolution:   => fixed


 Replying to [comment:4 taeuber]:
 > What/who does »ow« or »oh« define?

 oh and ow are useful if you want to reference ow/oh in the other
 expressions, for example to get a square output:

 in this case you define ow in the first expression, and reference it in
 the second expression, in a similar way you can do:

 what you can do is to self-reference ow/oh in the corresponding

 > Other filters?

 > Are »ih« and »iw« changed by the scale filter?

 No they are the input width and height, which are fixed.

 > I thought before any filters apply that "ow=iw" and "oh=ih". And the
 crop filter for instance changes the "oh" and "ow" automatically by
 subtracting the cropped lines/rows.
 > Wouldn't this make sense?

 That's possible, but I think the current behavior is not completely
 misguided, expressing something like
 x=x is inherently confusing, better to just say explicitely scale=iw:ih/2.

 > Thanks

 I clarified the error message in:
 commit 3af5ddb24b91cfa6e2392b85ef1beafda7e85225
 Author: Stefano Sabatini <stefasab at gmail.com>
 Date:   Sun Dec 4 23:33:40 2011 +0100

     vf_scale: give a clue in case of invalid expression self-reference

     Address trac ticket #706.

 changing status to closed, please provide a patch or suggest if you think
 this behavior can be clarified/improved.

Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/706#comment:5>
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