Is it possible to autocrop black borders of a video with ffmpeg?

Question

I think it has a "blackness" video filter, which can determine if a picture sequence is black. Maybe it also has a filter to determine crop values automatically to remove black borders form edges of a video. Or maybe it is possible somehow to write a script using the "blackness" filter.

score 37 · Answer 1 · edited Dec 05 '19 at 11:23

37

Yes, it is possible.

First play your video to see if it is OK:

ffplay -i YourMovie.mp4 -vf "cropdetect=24:16:0"

The cropdetect filter values are:

cropdetect=limit:round:reset

limit = black threshold (default 24)
round = output resolution must be divisible to this
reset = after how many frames the detection process will start over

If it looks OK, crop it:

ffmpeg -i YourMovie.mp4 -vf "crop=640:256:0:36" YourCroppedMovie.mp4

Source and more info: René Calles blog renevolution.com

edited Dec 05 '19 at 11:23

JoeNyland

286

answered Jun 24 '14 at 15:14

Cornelius

2,784
1
16
26

11

It might be helpful to put a start point (-ss 00:05:00) in when using cropdetect (before input -i) as some video will have a solid black screen when starting. – Jul 04 '15 at 13:45
I would like to use this to crop python matplotlib.animation videos, which have a white border. Is it possible to alter the color of the border being detected? – ryanjdillon Oct 08 '15 at 11:51
1

Can you specify something else than black as border color? White for example? – DanMan Mar 08 '18 at 13:03
This does not answer the question as you still need to do manual action – Freedo Sep 08 '19 at 08:32
Hey @Cornelius can you please help me to find one command
- i want to crop video.mp4 from Square to Round using ffmpeg - not want to use overlay command for this
– Adil Sep 13 '19 at 07:08
1

Your ffplay cropdetect command played my video but still had black on the right and bottom sides. Then I saw https://superuser.com/a/1035399/74576. And it occurs to me that maybe https://ffmpeg.org/ffmpeg-filters.html#cropdetect can't help at all for videos that have black sides of asymmetrical thicknesses. The documentation is not great. – Ryan May 24 '20 at 13:47
A manual crop worked for my case: https://ffmpeg.org/ffmpeg-filters.html#crop ffplay -i "myvid.mp4" -vf "crop=w=1104:h=830:x=0:y=0" – Ryan May 24 '20 at 13:57

score 19 · Answer 2 · edited May 23 '17 at 12:41

19

From: https://stackoverflow.com/questions/17265381/ffmpeg-get-value-from-cropdetect

ffmpeg -i input -t 1 -vf cropdetect -f null - 2>&1 | awk '/crop/ { print $NF }' | tail -1

edited May 23 '17 at 12:41

Community

1

answered Feb 20 '15 at 17:59

Jannes

290

1

ok, this will generate the "crop values" to use with ffmpeg in a simple and very clear way :), thx! – Aquarius Power Apr 13 '16 at 00:11
1

This fails miserably if there's a bit of black at the beginning of the video, such as in an intro. This is solved by adding -ss 5 before -i, to run cropdetect after skipping the first 5 seconds. – Hashim Aziz Apr 05 '21 at 19:11
1

Save yourself a fork and get awk to only print the last matching field. awk '/crop=/ {a=$NF} END{print a}' – Cliff Jul 06 '23 at 22:50
this line does NOTHING, where is the file name? – tribbloid Nov 26 '23 at 20:07
It's the "input" – Jannes Nov 28 '23 at 00:16

score 5 · Answer 3 · answered Jan 28 '18 at 20:27

Putting the other two answers together into a script:

#!/bin/sh
#ffmpeg_zoom ver 20180128202453
I="$@";X=${I##*.};O=${I%.*}_zoomed.${X};f=$(which ffmpeg 2>/dev/null)
if [ ! "$f" ]||[ "$f" = '' ];then echo "Install ffmpeg";exit 1;fi
C=$($f -i "$I" -t 1 -vf cropdetect -f null - 2>&1|awk '/crop/{print $NF}'|tail -n1)
echo $f -i "$I" -vf "$C" "$O"; $f -i "$I" -vf "$C" "$O"

This question has some relevant ffmpeg examples

Is it possible to autocrop black borders of a video with ffmpeg?

3 Answers3

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