[SOLVED] Need to detect if a video has black borders

I can detect the black borders on a video and create a crop= parameter for ffmpeg like this:

# detect the cropping parameters
FFREPORT=file=CROPDATA.txt:level=32 ffmpeg -hide_banner -loglevel quiet -ss $1 -i $2  -vframes 2 -vf "cropdetect=24:16:0" -f null -

# Extract the cropping paramaters for the -vf switch
CROP=`awk  '/crop=/ {print $14}' CROPDATA.txt`

This works just fine

$ echo $CROP
crop=976:720:156:0

What I want to do is to check the last two crop parameters x and y and if both are zero the vdio has no black borders.


How can I extract these two values, 156 and 0.


What i would do is add these together and if their sum is zero then there is no border. If it's greater thatn one there is a border and my script can take the appropriate action


Seems simple, but I can't figure it out!

This is the best I've come up with

CROP=crop=976:720:156:0
LAST3=${CROP#*:}
LAST2=${LAST3#*:}
THIRD=${LAST2%:*}
FOURTH=${LAST2#*:}

echo $THIRD $FOURTH
156 0

TOTAL=$(($THIRD + $FOURTH))
echo $TOTAL
156

So if there are black borders then TOTAL will not be zero

If there are no black borders then TOTAL will be zero

Is there a neater/more concise way?

If you are getting the crop parameter with awk anyway, why not extract the sum of two values immediately as well?

<<! read CROP TOTAL
$(awk '/crop=/ {
    split($14, a, /:/)
    print $14, a[3]+a[4]
  }' CROPDATA.txt)
!

or in Bash

read CROP TOTAL < <(
  awk '/crop=/ {
    split($14, a, /:/)
    print $14, a[3]+a[4]
  }' CROPDATA.txt)

Originally Posted by shruggy If you are getting the crop parameter with awk anyway, why not extract the sum of two values immediately as well? <<! read CROP TOTAL $(awk '/crop=/ { split($14, a, ":") print $14, a[3]+a[4] }' CROPDATA.txt) !

Cheers Shruggy, I just don't know awk that well, I did look and this is exactly how I thought to do it - thanks

Hey Shruggy,

So I included your code like this:

<<! read CROP TOTAL
TOTAL=$(awk '/crop=/ {
    split($14, a, ":")
    print $14, a[3]+a[4]
  }' CROPDATA.txt)
!

Could you explain what <<! read CROP TOTAL and the last ! do please
Cheers

See 3.6.6 Here Documents in the GNU Bash Manual.

The usual way to write them is

read CROP TOTAL <<END
TOTAL=$(awk '/crop=/ {
    split($14, a, /:/)
    print $14, a[3]+a[4]
  }' CROPDATA.txt)
END

Here the output of awk is read into two variables: CROP and TOTAL. In Bash, you can achieve the same with the here string (<<<) or with the process redirection.

Originally Posted by shruggy See 3.6.6 Here Documents in the GNU Bash Manual. The usual way to write them is read CROP TOTAL <<END TOTAL=$(awk '/crop=/ { split($14, a, /:/) print $14, a[3]+a[4] }' CROPDATA.txt) END Here the output of awk is read into two variables: CROP and TOTAL. In Bash you can achieve the same with the here string (<<<) or with the process redirection.

Many thanks, everyday is a school day, that was very helpful