How can I crop a video with ffmpeg?

Question

I have an MP4 file of a screen recording that I need to crop down. How can I accomplish this without using expensive tools like Adobe Premier or Final Cut? I prefer ffmpeg because I have used it before.

Answer 1

Use the crop filter:

ffmpeg -i in.mp4 -filter:v "crop=out_w:out_h:x:y" out.mp4

Where the options are as follows:

• out_w is the width of the output rectangle
• out_h is the height of the output rectangle
• x and y specify the top left corner of the output rectangle (coordinates start at (0,0) in the top left corner of the input)

Original image

_{Original 320x240 image}

How out_w, out_h, w and h fit into the picture

Example 1

To crop a 80×60 section, starting from position (200, 100):

ffmpeg -i in.mp4 -filter:v "crop=80:60:200:100" -c:a copy out.mp4

• The audio is stream copied in this example, so re-encoding is avoided.

Example 2

To crop the bottom right quarter:

ffmpeg -i in.mp4 -filter:v "crop=in_w/2:in_h/2:in_w/2:in_h/2" -c:a copy out.mp4

This is the same as:

ffmpeg -i in.mp4 -filter:v "crop=320/2:240/2:320/2:240/2" -c:a copy out.mp4

Which is the same as:

ffmpeg -i in.mp4 -filter:v "crop=160:120:160:120" -c:a copy out.mp4

• You can refer to the input image size with in_w and in_h as shown in this first example. The output width and height can also be used with out_w and out_h.

Example 3

Crop 20 pixels from the top, and 20 from the bottom:

 ffmpeg -i in.mp4 -filter:v "crop=in_w:in_h-40" -c:a copy out.mp4

• The filter will automatically center the crop if x and y are omitted such as in this example.

Previewing

You can take a crop (heh heh) and preview it live with ffplay:

ffplay -i input -vf "crop=in_w:in_h-40"

This way you can experiment and adjust your cropping without the need to encode, view, repeat.

Notes

• crop filter documentation

• Default encoder for MP4 is libx264 (H.264 video) or mpeg4 (MPEG-4 Part 2 video) depending on your ffmpeg build. See FFmpeg Wiki: H.264 Video Encoding Guide for more info.

• Instead of cropping and re-encoding, consider cropping upon playback. This is possible with any player worth using.

• Ancient ffmpeg builds used -croptop, -cropbottom, -cropleft, -cropright options instead of the crop filter. If this is the case for you then get a modern ffmpeg. Development is very active and there is no reason to use an antique.