FFMPEG - Crop Video
The following command will crop your video to the left side of the video using the first 1920 x 1080 pixels. This is useful if you accidentally recorded two 1080p monitors and just want the left one.
TOP_LEFT_X=0 TOP_LEFT_Y=0 WIDTH=1920 HEIGHT=1080 ffmpeg \ -i input.mp4 \ -filter:v "crop=$WIDTH:$HEIGHT:$TOP_LEFT_X:$TOP_LEFT_Y" \ output.mp4
Unfortunately, this will be re-encoding the video, so you may want to add a few options like:
TOP_LEFT_X=0 TOP_LEFT_Y=0 WIDTH=1920 HEIGHT=1080 ffmpeg \ -i input.mkv \ -preset slow \ -crf 17 \ -c:a copy \ -filter:v "crop=$WIDTH:$HEIGHT:$TOP_LEFT_X:$TOP_LEFT_Y" \ output.mkv
You will want to test that your setting are correct before kicking off a re-encoding. You can do this by using ffplay. E.g.
TOP_LEFT_X=0 TOP_LEFT_Y=0 WIDTH=1920 HEIGHT=1080 ffplay \ -vf crop=$WIDTH:$HEIGHT:$TOP_LEFT_X:$TOP_LEFT_Y \ input.mp4
Crop Using Bitstream Filter
The previous command will result in doing a re-encode of the video, which will work on any video format, but you are performing a re-encode, so you are likely to lose quality and have to tweak the other ffmpeg settings like CRF etc. To get around this, for h264 and h265 videos, you can set some metadata in the video so it will just play back cropped instead, so you are not changing the video track itself.
ffmpeg \ -i input.mp4 \ -c copy \ -bsf:v h264_metadata=crop_left=0:crop_right=0:crop_top=130:crop_bottom=130 \ output.mp4
Recorded Entire Desktop And Want Just One Screen
The following would be useful if you had two 1920x1080p monitors side-by-side and you accidentally recorded your entire desktop, instead of just your left monitor:
ffmpeg \ -i input.mp4 \ -filter:v "crop=1920:1080:0:0" \ output.mp4
Likewise, if you wanted to keep the right monitor instead:
ffmpeg \ -i input.mp4 \ -filter:v "crop=1920:1080:1920:0" \ output.mp4
Remove Black Bars
Sometimes movie files will be "letterboxed" so that they will always show black bars. This is really aggravating as you may wish to show the movie on a variety of screen aspect ratios, which can lead to black bars on the right and left too.
In my 1920 x 1080p movie, I had letterbox bars of height 130px, but it applies to top and bottom, so you have to subtract 130 from the 1080p height that you are cropping to get:
ffmpeg \ -i input.mp4 \ -filter:v "crop=1920:820:0:130" \ output.mp4
- Video Stack Exchange - How can I crop a video with ffmpeg?
- Superuser - Remove .mp4 video top and bottom black bars using ffmpeg
- FFMPEG: crop a video without losing the quality
First published: 4th March 2020