#!/bin/bash
# joinvideos.sh v1.5 by Saugata
# join multiple video files with ffmpeg 

# remove temp files if they exist from interrupted past run
if ls temp-*.mp4 1> /dev/null 2>&1; then
  echo "Removing older temp*.mp4 files"
  rm temp-*.mp4
fi

# make a list of all mp4 files in the diretory 
# except the output.mp4 if it exists
listofvidfiles=`ls -1 | grep mp4 | grep -v "output"`

for f in $listofvidfiles;
do
  # check for location of Video stream
  # if Video is at Stream #0:1 then swap to Stream #0:0
  # save file as temp file
  vidstreamno=`ffprobe $f 2>&1 | grep Video | cut -d":" -f2 | cut -d"(" -f1`
  if [ "$vidstreamno" -eq "1" ]; then
    ffmpeg -i $f -map 0:1 -map 0:0 -c copy temp-$f
  else
    cp $f temp-$f
  fi
  # if Video is at Stream #0:0 then copy it to a temp file
  echo $f: "Video stream at" $vidstreamno
done

# create a text files from list of temp-*.mp4 for ffmpeg input
ls -1 *.mp4 | grep mp4 | grep temp | sed "s/^/file '/" | sed "s/$/\'/" > vidfilelist.txt 
echo "-----------------------------"
echo "Joining files ..............."
cat vidfilelist.txt 
echo "-----------------------------"

# use ffmpeg to join mp4 files
ffmpeg -f concat -safe 0 -i vidfilelist.txt -c copy output.mp4

# clean temp files before exit
if ls temp-*.mp4 1> /dev/null 2>&1; then
  echo "Removing temp*.mp4 files"
  rm temp-*.mp4
fi

ffmpeg -f concat -safe 0 -i mylist.txt -c copy output.mp4

# this is a comment
file 'f1.mp4'
file 'f2.mp4'

[mp4 @ 0x559118faf340] Non-monotonous DTS in output stream 0:1; previous: 10392576, current: 9748800; changing to 10392577. This may result in incorrect timestamps in the output file.

$ ffmpeg -i f2.mp4 -map 0:1 -map 0:0 -c copy  new.mp4