diff --git a/to_opus(1).sh b/to_opus(1).sh
new file mode 100644
index 0000000..489746e
--- /dev/null
+++ b/to_opus(1).sh
@@ -0,0 +1,75 @@
+#!/bin/bash
+
+# set shopt-options used by this shell-script
+# Note, 0 (true) from shopt -q is "false" in a math context.
+shopt -q globstar; globstar_set=$?
+((globstar_set)) && shopt -s globstar
+shopt -q extglob; extglob_set=$?
+((extglob_set)) && shopt -s extglob
+
+# return default shopt-options
+function finish {
+	((globstar_set)) && shopt -u globstar
+	((extglob_set)) && shopt -u extglob
+}
+trap finish EXIT
+
+print_usage() {
+  printf "Usage: ..."
+}
+
+extension=''
+
+while getopts 'e:' flag; do
+  case "${flag}" in
+    e) extension+=("$OPTARG");;
+    *) print_usage
+       exit 1 ;;
+  esac
+done
+
+# write array into string
+extension="${extension[*]}"
+# remove leading space
+extension="${extension##+([[:space:]])}"
+# change separator
+echo "$extension"
+extension=${extension// /|}
+
+for file in **/*.@($extension); do
+	
+	#set a channel-dependent  bitrate for every audio stream
+	command=$(
+		ffprobe "$file" -v 0 -show_entries stream=channels,bit_rate -select_streams a -of compact=p=0:nk=1:s="\ " |
+		awk -v file="$file" -v file_output="${file%.*}.opus" '
+			BEGIN{
+				ORS=" ";
+				print "ffmpeg -i \""file"\" -map 0:a -c:a libopus"
+			}
+			{	# https://wiki.xiph.org/Opus_Recommended_Settings
+				if($1==1) print $2>=64000 ? "-b:a:"NR-1" 64k" : "-b:a:"NR-1" "$2
+				else if($1==2) print $2>=128000 ? "-b:a:"NR-1" 128k" : "-b:a:"NR-1" "$2
+				else if($1<=6) print $2>=256000 ? "-b:a:"NR-1" 256k" : "-b:a:"NR-1" "$2
+				else print $2>=450000 ? "-b:a:"NR-1" 450k" : "-b:a:"NR-1" "$2
+			}
+			END{
+				print "\""file_output"\" -v info -hide_banner"
+			}')
+
+
+	is_video=$(ffprobe -i Hair.m4v -v fatal -select_streams V -show_entries stream=codec_type)
+	if [[ -n "$is_video" ]]; then
+		echo "$file is a video file and will not be converted"
+
+		#an Example for converting the audiostreams in a container while copying subtitles and videostreams.
+		#ffmpeg -i Hair.m4v -map 0:a -map 0:s -map 0:v -c:a libopus -c:v copy -c:s copy Hair.mkv -hide_banner -v info
+
+		#for extracting the audiostreams of a video file just use "eval "$command"".
+		#it is recommended to check the result before deleting the original file.
+	else
+		eval "$command" #&& rm "$file"
+	fi
+
+done
+
+exit 0