Normalize mp3 scripts (#143)

scripts/normalize.sh

@@ -0,0 +1,46 @@
+#!/bin/bash
+
+TEMP_FILE=temp.mp3
+PADDED_FILE=paddedNormalized.temp.mp3
+
+# Check than ffmpeg && ffmpeg-normalize is installed
+if ! [ -x "$(command -v ffmpeg)" ]; then
+  echo 'Error: ffmpeg is not installed.' >&2
+  exit 1
+fi
+if ! [ -x "$(command -v ffmpeg-normalize)" ]; then
+  echo 'Error: ffmpeg-normalize is not installed.' >&2
+  exit 1
+fi
+
+# Check that input mp3 is present & exist
+if [ -n "$1" ]
+then
+  inputFile=$1
+else
+  echo 'Error: missing input file' >&2
+  exit 1
+fi
+if [ ! -f ./$inputFile ]; then
+    echo "File not found!"
+fi
+
+cleanup () {
+  rm -f $TEMP_FILE
+  rm -f $PADDED_FILE
+  rm -f final.mp3
+}
+
+cleanup
+
+# Normalize the file
+# Due to an issue with ffmpeg-normalize, file shorter than 3s cannot be normalized
+# The following use a solution from https://github.com/slhck/ffmpeg-normalize/issues/87#issuecomment-488944192
+ffmpeg -i $inputFile -af "adelay=10000|10000" $TEMP_FILE
+
+ffmpeg-normalize $TEMP_FILE -o $PADDED_FILE -c:a libmp3lame
+
+ffmpeg -i $PADDED_FILE -ss 00:00:10.000 -acodec copy $inputFile -y
+
+cleanup
+