Add paddings to the input image, and place the original input at the given coordinates x, y.
This filter accepts the following parameters:
- width, w, height, h
-
Specify an expression for the size of the output image with the paddings added. If the value for width or height is 0, the corresponding input size is used for the output.
The width expression can reference the value set by the height expression, and vice versa.
The default value of width and height is 0.
- x, y
-
Specify an expression for the offsets where to place the input image in the padded area with respect to the top/left border of the output image.
The x expression can reference the value set by the y expression, and vice versa.
The default value of x and y is 0.
- color
-
Specify the color of the padded area. For the syntax of this option, check the "Color" section in the ffmpeg-utils manual.
The default value of color is "black".
The value for the width, height, x, and y options are expressions containing the following constants:
- in_w, in_h
-
the input video width and height
- iw, ih
-
same as in_w and in_h
- out_w, out_h
-
the output width and height, that is the size of the padded area as specified by the width and height expressions
- ow, oh
-
same as out_w and out_h
- x, y
-
x and y offsets as specified by the x and y expressions, or NAN if not yet specified
- a
-
same as iw / ih
- sar
-
input sample aspect ratio
- dar
-
input display aspect ratio, it is the same as (iw / ih) * sar
- hsub, vsub
-
horizontal and vertical chroma subsample values. For example for the pixel format "yuv422p" hsub is 2 and vsub is 1.
Examples
-
Add paddings with color "violet" to the input video. Output video size is 640x480, the top-left corner of the input video is placed at column 0, row 40:
pad=640:480:0:40:violet
The example above is equivalent to the following command:
pad=width=640:height=480:x=0:y=40:color=violet
-
Pad the input to get an output with dimensions increased by 3/2, and put the input video at the center of the padded area:
pad="3/2*iw:3/2*ih:(ow-iw)/2:(oh-ih)/2"
-
Pad the input to get a squared output with size equal to the maximum value between the input width and height, and put the input video at the center of the padded area:
pad="max(iw\,ih):ow:(ow-iw)/2:(oh-ih)/2"
-
Pad the input to get a final w/h ratio of 16:9:
pad="ih*16/9:ih:(ow-iw)/2:(oh-ih)/2"
-
In case of anamorphic video, in order to set the output display aspect correctly, it is necessary to use sar in the expression, according to the relation:
(ih * X / ih) * sar = output_dar X = output_dar / sar
Thus the previous example needs to be modified to:
pad="ih*16/9/sar:ih:(ow-iw)/2:(oh-ih)/2"
-
Double output size and put the input video in the bottom-right corner of the output padded area:
pad="2*iw:2*ih:ow-iw:oh-ih"