Script to combine multiple videos into one

Use cases: add intro, outro and other clips to a video

combinevideos.sh

@@ -0,0 +1,122 @@
+#!/bin/bash
+
+# Purpose of this code: Combine multiple videos to create one single video
+# Input : combinevideos file_containing_list_of_files.txt
+# Structure of file_containing_list_of_files.txt is as follows \/
+# file myfile1.mp4
+# file myfile2.mp4 ...
+
+# Output: New file will be created with the name combined2files_myfile1_myfile2.mp4
+
+FILE_LIST=$1
+
+filescount=$(wc -l $FILE_LIST | awk '{ print $1 }')
+finalfilepath="combined${filescount}files"
+
+echo "Going to combine following videos as mentioned in ${FILE_LIST}..."
+
+function float_gt() {
+    perl -e "{if($1>$2){print 1} else {print 0}}"
+}
+
+
+count=1
+largest_duration=0;
+longest_video="";
+timebase_of_largest_video=0;
+filearray=()
+while IFS= read -r line
+do 
+  #process only lines which start with keyword 'file'
+  keyword=$(echo $line | awk -F'[ ]' '{ print $1 }')
+  if [ "$keyword" != "file" ]
+  then
+	#the line doesn't start with keyord file, ignore
+	continue
+  fi
+  filepath=$(echo $line | awk -F'[ ]' '{ print $2 }')
+  filearray+=("$filepath")
+  base=$(echo $filepath | sed 's/\.[^.]*$//')
+  timebase=$(ffprobe -loglevel warning -show_streams $filepath | awk '/^time_base/' | awk -F\= '{ "basename "$1"" |& getline $1; print $2;exit}'|awk -F\/ '{print $2}')
+  duration=$(ffprobe -loglevel warning -v error -show_entries format=duration  -of default=noprint_wrappers=1:nokey=1 $filepath)
+  echo "${count}: $filepath ; duration: $duration s; time_base: $timebase"
+  count=$[$count+1]
+  #Find the longest video and remeber it's timebase
+  if [ $(float_gt $duration $largest_duration) == 1 ]
+  then
+  	largest_duration=$duration
+        timebase_of_largest_video=$timebase
+        longest_video="$filepath"
+  fi
+  #finalfilepath generation: apending all file names except when filename exceeds 30 characters
+  if [ ${#finalfilepath} -lt 30 ]
+  then
+	finalfilepath="${finalfilepath}_$base"
+  fi
+done < "$FILE_LIST"
+
+finalfilepath="${finalfilepath}.mp4"
+
+echo ""
+echo -e "\e[1mLongest video is $longest_video\e[0m with duration: $largest_duration and \e[1mtimebase: $timebase_of_largest_video\e[0m"
+echo ""
+
+#Step 1 : Fix the time_base of all videos(why? detail in the references section of this script)
+newfilearray=()
+setTimeBase(){	
+  timebase=$(ffprobe -loglevel warning -show_streams $1 | awk '/^time_base/' | awk -F\= '{ "basename "$1"" |& getline $1; print $2;exit}'|awk -F\/ '{print $2}')
+  #if timebase is different than what we want to fix, create a temporary video with new timebase
+  if [ $timebase -ne $2 ]
+  then
+	  tmp_filename="tmp_${2}_$1"
+	  echo -e "\e[7mChanging timebase for file: $1 from $timebase to $2 tbn and saving new file at $tmp_filename\e[0m"
+	  ffmpeg -loglevel warning -i $1 -video_track_timescale $2 $tmp_filename
+          newfilearray+=("$tmp_filename")
+  else
+	newfilearray+=("$1")
+  fi
+}
+
+for i in ${!filearray[@]}; do
+  setTimeBase ${filearray[$i]} $timebase_of_largest_video
+done
+
+#create a new text file to store all file names that we want to concat
+newfilelistwithsyncdtimebase="tmp_combine_file_list"
+
+for i in ${!newfilearray[@]}; do
+  filepath="${newfilearray[$i]}"
+  base=$(echo $filepath | sed 's/\.[^.]*$//')
+  newfilelistwithsyncdtimebase="${newfilelistwithsyncdtimebase}_$base" 
+done
+
+newfilelistwithsyncdtimebase="${newfilelistwithsyncdtimebase}.txt" 
+
+if [ ! -f "$newfilelistwithsyncdtimebase" ]
+then
+	echo "Creating file ${newfilelistwithsyncdtimebase}"
+	touch $newfilelistwithsyncdtimebase
+else
+	echo "File '${newfilelistwithsyncdtimebase}' already exists. Remove it and run this again to create a new combined video."
+	exit
+fi
+
+for i in ${!newfilearray[@]}; do
+  echo "file ${newfilearray[$i]}" >> $newfilelistwithsyncdtimebase
+done
+
+
+echo ""
+echo "Preparing output $finalfilepath"
+echo ""
+
+#Step 2: concatenate the files using the updated list of files
+ffmpeg -f concat -safe 0 -i $newfilelistwithsyncdtimebase -copytb 0 -c copy -loglevel warning $finalfilepath 
+
+
+# References
+# -loglevel warning for less verbose command print
+# -c copy to skip encoding the videos again
+
+# ISSUE: DTS out of order https://stackoverflow.com/a/56002050/7360184 (unexpected output when encoding does not match)
+# To solve this issue here, we set all videos' timebase to be same as the longest video's timebase