crop - FFmpeg 1.2.12 / Filters / Video

Crop the input video.

This filter accepts a list of key=value pairs as argument, separated by ’:’. If the key of the first options is omitted, the arguments are interpreted according to the syntax out_w:out_h:x:y:keep_aspect.

A description of the accepted options follows:

w, out_w: Set the crop area width. It defaults to iw. This expression is evaluated only once during the filter configuration.
h, out_h: Set the crop area height. It defaults to ih. This expression is evaluated only once during the filter configuration.
x: Set the expression for the x top-left coordinate of the cropped area. It defaults to (in_w-out_w)/2. This expression is evaluated per-frame.
y: Set the expression for the y top-left coordinate of the cropped area. It defaults to (in_h-out_h)/2. This expression is evaluated per-frame.
keep_aspect: If set to 1 will force the output display aspect ratio to be the same of the input, by changing the output sample aspect ratio. It defaults to 0.

The out_w, out_h, x, y parameters are expressions containing the following constants:

x, y: the computed values for x and y. They are evaluated for each new frame.
in_w, in_h: the input width and height
iw, ih: same as in_w and in_h
out_w, out_h: the output (cropped) width and height
ow, oh: same as out_w and out_h
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.
n: the number of input frame, starting from 0
pos: the position in the file of the input frame, NAN if unknown
t: timestamp expressed in seconds, NAN if the input timestamp is unknown

The expression for out_w may depend on the value of out_h, and the expression for out_h may depend on out_w, but they cannot depend on x and y, as x and y are evaluated after out_w and out_h.

The x and y parameters specify the expressions for the position of the top-left corner of the output (non-cropped) area. They are evaluated for each frame. If the evaluated value is not valid, it is approximated to the nearest valid value.

The expression for x may depend on y, and the expression for y may depend on x.

Examples

Crop area with size 100x100 at position (12,34).
```
crop=100:100:12:34
```
Using named options, the example above becomes:
```
crop=w=100:h=100:x=12:y=34
```
Crop the central input area with size 100x100:
```
crop=100:100
```
Crop the central input area with size 2/3 of the input video:
```
crop=2/3*in_w:2/3*in_h
```
Crop the input video central square:
```
crop=in_h
```
Delimit the rectangle with the top-left corner placed at position 100:100 and the right-bottom corner corresponding to the right-bottom corner of the input image:
```
crop=in_w-100:in_h-100:100:100
```
Crop 10 pixels from the left and right borders, and 20 pixels from the top and bottom borders
```
crop=in_w-2*10:in_h-2*20
```
Keep only the bottom right quarter of the input image:
```
crop=in_w/2:in_h/2:in_w/2:in_h/2
```
Crop height for getting Greek harmony:
```
crop=in_w:1/PHI*in_w
```

Appply trembling effect:

crop=in_w/2:in_h/2:(in_w-out_w)/2+((in_w-out_w)/2)*sin(n/10):(in_h-out_h)/2 +((in_h-out_h)/2)*sin(n/7)

Apply erratic camera effect depending on timestamp:

crop=in_w/2:in_h/2:(in_w-out_w)/2+((in_w-out_w)/2)*sin(t*10):(in_h-out_h)/2 +((in_h-out_h)/2)*sin(t*13)"

Set x depending on the value of y:
```
crop=in_w/2:in_h/2:y:10+10*sin(n/10)
```