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Diffstat (limited to 'doc')
-rw-r--r-- | doc/filters.texi | 60 |
1 files changed, 55 insertions, 5 deletions
diff --git a/doc/filters.texi b/doc/filters.texi index 1a26f10c59..669a334eca 100644 --- a/doc/filters.texi +++ b/doc/filters.texi @@ -772,13 +772,33 @@ can be used to test the monowhite pixel format descriptor definition. Scale the input video to @var{width}:@var{height} and/or convert the image format. -For example the command: +The parameters @var{width} and @var{height} are expressions containing +the following constants: -@example -./ffmpeg -i in.avi -vf "scale=200:100" out.avi -@end example +@table @option +@item E, PI, PHI +the corresponding mathematical approximated values for e +(euler number), pi (greek PI), phi (golden ratio) + +@item in_w, in_h +the input width and heigth + +@item iw, ih +same as @var{in_w} and @var{in_h} + +@item out_w, out_h +the output (cropped) width and heigth + +@item ow, oh +same as @var{out_w} and @var{out_h} -will scale the input video to a size of 200x100. +@item a +input display aspect ratio, same as @var{iw} / @var{ih} + +@item hsub, vsub +horizontal and vertical chroma subsample values. For example for the +pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1. +@end table If the input image format is different from the format requested by the next filter, the scale filter will convert the input to the @@ -793,6 +813,36 @@ ratio of the input image. The default value of @var{width} and @var{height} is 0. +Some examples follow: +@example +# scale the input video to a size of 200x100. +scale=200:100 + +# scale the input to 2x +scale=2*iw:2*ih +# the above is the same as +scale=2*in_w:2*in_h + +# scale the input to half size +scale=iw/2:ih/2 + +# increase the width, and set the height to the same size +scale=3/2*iw:ow + +# seek for Greek harmony +scale=iw:1/PHI*iw +scale=ih*PHI:ih + +# increase the height, and set the width to 3/2 of the height +scale=3/2*oh:3/5*ih + +# increase the size, but make the size a multiple of the chroma +scale="trunc(3/2*iw/hsub)*hsub:trunc(3/2*ih/vsub)*vsub" + +# increase the width to a maximum of 500 pixels, keep the same input aspect ratio +scale='min(500\, iw*3/2):-1' +@end example + @anchor{setdar} @section setdar |