#!/bin/bash
#B. Vandeportaele
#script to concatenate video files from the GOPRO using ffmpeg

#if the filenames are not in sequence as generated by the script, a list of file can be used. The file containing the list should be 
#made of lines such as:     file 'GOPR0650.MP4'
#ffmpeg -f concat -safe 0 -i  file-list_to_concatenate.txt  -ss 1:16 -t 30:00  -c copy GOPR0650_complete_cut.MP4

NUMBER=0711
START_TIME="0:19"
DURATION="2:0:00"

#construct a string that contains all the necessary file names
#LIST="\"concat:GOPR$NUMBER.MP4|GP01$NUMBER.MP4\""
#LIST="GOPR$NUMBER.MP4|GP01$NUMBER.MP4|GP02$NUMBER.MP4|GP03$NUMBER.MP4|GP04$NUMBER.MP4|GP05$NUMBER.MP4|GP06$NUMBER.MP4|GP07$NUMBER.MP4|GP08$NUMBER.MP4|GP09$NUMBER.MP4"

#begin with a list of 1 file
LIST="\"concat:GOPR$NUMBER.MP4"
echo $LIST


#loop for 10 next files and try to detect if the file exists then add it to the list
for I in `seq -w 1 10`;
  do
  file="GP$I$NUMBER.MP4"
  if [ -f "$file" ]
    then
      echo "$file found."
      LIST="$LIST|$file"
    else
      echo "$file not found."
  fi
done

#close the list
LIST="$LIST\""
echo $LIST

#on peut aussi éviter de passer par une liste de fichier et utiliser 
# -i "concat:input1.mpg|input2.mpg|input3.mpg"

#generate an output file name
OUTFILE="GOPR${NUMBER}_completecut.MP4"
#generate the command
COMMAND="ffmpeg   -i $LIST  -ss $START_TIME -t $DURATION -c copy $OUTFILE"
echo "Do you want to execute the following command (y/n):"
echo $COMMAND
read line
if  [ "$line" == "y" ]; then
  #execute the command in the variable
  eval "$COMMAND"
fi