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.
1 Answer
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 rectangleout_h
is the height of the output rectanglex
andy
specify the top left corner of the output rectangle
Original image
Original 320x240 image
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
andin_h
as shown in this first example. The output width and height can also be used without_w
andout_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
andy
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
Default encoder for MP4 is
libx264
(H.264 video) ormpeg4
(MPEG-4 Part 2 video) depending on yourffmpeg
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 thecrop
filter. If this is the case for you then get a modernffmpeg
. Development is very active and there is no reason to use an antique.
-
3
-
3worth to mention this technique (with the
crop
filter) re-encodes the video, see stackoverflow.com/questions/33378548/… if re-encoding matters for you– abernierOct 14, 2017 at 9:58 -
2edited to change the outdated
-filter:v
to the more up to date and simpler to type-vf
. Cheers! Dec 15, 2017 at 0:35 -
9If you're trying to remove black bars around your video (piallarbox, letterbox, windowbox etc.) use
cropdetect
first to have ffmpeg print cropping parameters for you:ffmpeg.exe -i vid.mp4 -vf cropdetect out.mp4
– ShayanSep 6, 2019 at 21:38 -
4