[SOLVED] How to cut the last 1 min of a movie?

GPGAgent · 12-12-2018, 04:06 AM

Cut the last one minute of a movie? Sound simple enough and I've almost got it but my bash skills let me down on the simplest of things!

Step 1 get movie length - many ways here's one

Code:

jonk@XEON4 ~/CK $ ffprobe -i CK.mp4 -show_format -v quiet | sed -n 's/duration=//p'
301.040000

So that's a length of 301 seconds
Step 2 subtract 1 minute

Code:

jonk@XEON4 ~/CK $ echo $(( 301 - 60))
241

So that's a start point of 241 seconds, my -ss parameter for ffmpeg.

Step three combine all this in a script, I tried combining the first two steps

Code:

jonk@XEON4 ~/CK $ echo $(( $(ffprobe -i CK.mp4 -show_format -v quiet | sed -n 's/duration=//p') - 60))
bash: 301.040000 - 60: syntax error: invalid arithmetic operator (error token is ".040000 - 60")
jonk@XEON4 ~/CK $

So my question is how to combine a complex command in an arithmetic bash statement?

Or maybe there is another way to use ffmpeg to cut the last minute of a movie.

BTW I intend to loop through a folder of movies to cut the last minute from all of them which is why I want to parameterise this operation.

TIA

l0f4r0 · 12-12-2018, 04:47 AM

I won't debate about your ffprobe methodology because I've never used it so far. So I'll limit myself to answering you on a pure bash/shell point of view:

bash does not support floating-point arithmetic. You need to use an external utility like bc.
So try the following instead:

Code:

echo "scale=2;$(ffprobe -i CK.mp4 -show_format -v quiet | sed -n 's/duration=//p') - 60" | bc

pan64 · 12-12-2018, 04:54 AM

there are two ways in general: remove the decimal part (for example with sed):
sed -n '/duration/s/duration=//;s/\.[0-9][0-9]*//p'
or use bc.

GPGAgent · 12-12-2018, 12:51 PM

Quote:

Originally Posted by l0f4r0

I won't debate about your ffprobe methodology because I've never used it so far. So I'll limit myself to answering you on a pure bash/shell point of view:

bash does not support floating-point arithmetic. You need to use an external utility like bc.
So try the following instead:

Code:

echo "scale=2;$(ffprobe -i CK.mp4 -show_format -v quiet | sed -n 's/duration=//p') - 60" | bc

That works fine, thanks

GPGAgent · 12-12-2018, 12:54 PM

Okay, thanks folks, I should have spotted that bash only handles integers, so I have my script working that cuts the last x minutes from a set of movies.

I use ffmpeg -ss to skip to x mins from the end then just copy that chunk of movie, very simple, but is there a better way to chop out the last x mins from a set of movies?

teckk · 12-12-2018, 02:14 PM

Code:

#! /usr/bin/env bash

#Loop through all file in directory of videos
for i in *; do

    #Get duration of video
    duration=$(ffprobe -v error -show_entries format=duration -of default=noprint_wrappers=1:nokey=1 "$i")
    
    #Drop decimals, subtract 60 from duration
    dur=$((${duration%.*} - 60))
    
    #Echo ffmpeg command line
    echo "ffmpeg -t "$dur" -i "$i" -c:a copy -c:v copy NEW_"$i""
    
done

GPGAgent · 12-12-2018, 05:08 PM

Quote:

Originally Posted by teckk

Code:

#! /usr/bin/env bash

#Loop through all file in directory of videos
for i in *; do

    #Get duration of video
    duration=$(ffprobe -v error -show_entries format=duration -of default=noprint_wrappers=1:nokey=1 "$i")
    
    #Drop decimals, subtract 60 from duration
    dur=$((${duration%.*} - 60))
    
    #Echo ffmpeg command line
    echo "ffmpeg -t "$dur" -i "$i" -c:a copy -c:v copy NEW_"$i""
    
done

Basically that's what I've done

Code:

#!/bin/bash
renice 19 -p $$

bold=$(tput bold)
norm=$(tput sgr0)

default="*.mp4"
read -p "Movie Filename and Extension to Process [${bold}$default${norm}|*A|A*]: " FileNameAndExt
FileNameAndExt=${FileNameAndExt:-$default}

default=600
read -e -p "Get last part of movie  [${bold}$default${norm}] seconds from end: "  STARTAT
STARTAT=${STARTAT:-$default}        # -ss $STARTAT

echo "cutting ${FileNameAndExt} "

for FF in $FileNameAndExt;

    do ((COUNTER++)); 
            ss=$(echo "scale=2;$(ffprobe -i ${FF} -show_format -v quiet | sed -n 's/duration=//p') - $STARTAT" | bc)
      ffmpeg -i  ${FF} -ss ${ss} -c:v copy -c:a copy  "Last.${FF}"
    done

exit 0

Cheers

GPGAgent · 12-16-2018, 09:31 AM

just posted this:

https://www.linuxquestions.org/quest...in-4175644387/

A result of comments back from this thread.

Cheers all