Inserting code comments for the next guy.

AAXtoMP3

@@ -41,8 +41,9 @@ fi
 # Variable validation
 set -o errexit -o noclobber -o nounset -o pipefail
 
+# -----
+# Detect which annoying version fo grep we have
 GREP=$(grep --version | grep -q GNU && echo "grep" || echo "ggrep")
-
 if ! [[ $(type -P "$GREP") ]]; then
   echo "$GREP (GNU grep) is not in your PATH"
   echo "Without it, this script will break."
@@ -98,10 +99,13 @@ log() {
   echo "$(date "+%F %T%z") ${1}"
 }
 
+# Clean up if someone hits ^c
 trap 'rm -r -f "${working_directory}"' EXIT
 working_directory=`mktemp -d 2>/dev/null || mktemp -d -t 'mytmpdir'`
 metadata_file="${working_directory}/metadata.txt"
 
+# -----
+# Inspect the AAX and extract the metadata associated with the file.
 save_metadata() {
   local media_file
   media_file="$1"
@@ -110,16 +114,23 @@ save_metadata() {
   debug_file "$metadata_file"
 }
 
+# -----
+# Reach into the meta data and extract a specific value.
+#   Note the white space clean up could be well cleaner.
 get_metadata_value() {
   local key
   key="$1"
   normalize_whitespace "$($GREP --max-count=1 --only-matching "${key} *: .*" "$metadata_file" | cut -d : -f 2- | sed -e 's#/##g;s/ (Unabridged)//' | tr -s '[:blank:]' ' ')"
 }
 
+# -----
+# specific varient of get_metadata_value bitrate is important for transcoding.
 get_bitrate() {
   get_metadata_value bitrate | $GREP --only-matching '[0-9]\+'
 }
 
+# -----
+# simple function to turn tabs and multiple spaces into a single space.
 normalize_whitespace() {
   echo $*
 }
@@ -136,6 +147,8 @@ do
     exit 1
   fi
 
+  # -----
+  # Make sure everything is a variable.  Simplifying CMD interpretation
   save_metadata "${path}"
   genre=$(get_metadata_value genre)
   artist=$(get_metadata_value artist)
@@ -156,6 +169,8 @@ do
   # Big long DEBUG output.  Fully describes the settings used for transcoding.  I could probably do this better.
   debug "$(printf '\n%-18s: %s\n%-18s: %s\n%-18s: %s\n%-18s: %s\n%-18s: %s\n%-18s: %s\n%-18s: %s\n%-18s: %s\n%-18s: %s\n%-18s: %s\n%-18s: %s\n%-18s: %s\n%-18s: %s\n%-18s: %sn%-18s: %s' title "${title}" auth_code "${auth_code}" mode "${mode}" path "${path}" codec "${codec}" bitrate "${bitrate}" artist "${artist}" album_artist "${album_artist}" album "${album}" album_date "${album_date}" genre "${genre}" copyright "${copyright}" full_file_path "${full_file_path}" metadata_file "${metadata_file}" working_directory "${working_directory}" )"
 
+  # -----
+  # This is the main work horse command.  This is the primary transcoder.
   # This is the primary transcode. All the heavy lifting is here.
   </dev/null ffmpeg -loglevel error -stats -activation_bytes "${auth_code}" -i "${path}" -vn -codec:a "${codec}" -ab ${bitrate} -map_metadata -1 -metadata title="${title}" -metadata artist="${artist}" -metadata album_artist="${album_artist}" -metadata album="${album}" -metadata date="${album_date}" -metadata track="1/1" -metadata genre="${genre}" -metadata copyright="${copyright}" "${full_file_path}"
 
@@ -167,6 +182,8 @@ do
   log "Extracting cover into ${cover_path}..."
   </dev/null ffmpeg -loglevel error -activation_bytes "${auth_code}" -i "${path}" -an -codec:v copy "${cover_path}"    
 
+  # -----
+  # OK now spit the file if that's what you want.
   # If we want multiple file we take the big mp3 and split it by chapter.
   if [ "${mode}" == "chaptered" ]; then
     # Playlist m3u support
@@ -180,8 +197,7 @@ do
     chapternum=1
     while read -r -u9 first _ _ start _ end
     do
-            if [[ "${first}" = "Chapter" ]]
-            then
+      if [[ "${first}" = "Chapter" ]]; then
         read -r -u9 _
         read -r -u9 _ _ chapter
         chapter_title="${title} - $(printf %0${#chaptercount}d $chapternum) ${chapter}"
@@ -203,6 +219,7 @@ do
         -metadata:s:v title="Album cover" -metadata:s:v comment="Cover (Front)" -metadata track="${chapternum}" -metadata title="${chapter_title}" \
         "${chapter_file}"
         
+        # OK lets get what need for the next chapter in the Playlist m3u file.        
         duration=$(echo "${end} - ${start%?}" | bc)
         echo "#EXTINF:${duration%.*},${title} - ${chapter}" >>  "${playlist_file}"
         echo "${chapter_title}.${extension}" >> "${playlist_file}"