Convert FLAC to MP3

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Introduction

Here is a script that will convert FLAC to MP3 via the commandline.

Essentially, the .flac files within a directory will be decompressed to .wav and then the resulting .wav files will be encoded to .mp3 using the latest LAME switches for encodings (-V 0 --vbr-new). The ID3 tags of the original .flac files will be passed to the resulting .mp3 files.

The original .flac files will not be harmed and the resulting .mp3s will be in the same directory. All other files in the directory (.nfo, images, .sfv, etc) will be ignored and unharmed.

For more information on LAME switches/settings such as V0, visit Hydrogenaudio LAME Wiki. V0 is roughly equivalent to --preset extreme which results in a variable bitrate usually between 220-260. The audio of a V0 is transparent, meaning one cannot tell the difference between the lossy file and the original source (compact disc/lossless), but yet the file size is a quite reasonable.

More information on flac: FLAC

Installation

First you need to install the following packages: flac, lame, and id3

pacman -S flac lame id3

Once those are installed, copy the following script into your preferred editor:

#! /bin/sh

for a in *.flac; do
    OUTF=${a%.flac}.mp3

    ARTIST=$(metaflac "$a" --show-tag=ARTIST | sed s/.*=//g)
    TITLE=$(metaflac "$a" --show-tag=TITLE | sed s/.*=//g)
    ALBUM=$(metaflac "$a" --show-tag=ALBUM | sed s/.*=//g)
    GENRE=$(metaflac "$a" --show-tag=GENRE | sed s/.*=//g)
    TRACKNUMBER=$(metaflac "$a" --show-tag=TRACKNUMBER | sed s/.*=//g)
    DATE=$(metaflac "$a" --show-tag=DATE | sed s/.*=//g)

    flac -c -d "$a" | lame -m j -q 0 --vbr-new -V 0 -s 44.1 - "$OUTF"
    id3 -t "$TITLE" -T "${TRACKNUMBER:-0}" -a "$ARTIST" -A "$ALBUM" -y "$DATE" -g "${GENRE:-12}" "$OUTF"
done

Below is a modified version of the above script which:

  • adds an optional parameter (-d), which, if passed on the command line, causes each source FLAC file to be deleted after successful conversion;
  • changes the LAME encoding options as follows:
    • drops --vbr-new, as it is the default VBR behaviour as of LAME 3.98, and thus is automatically used when "-V 0" is used;
    • drops "-m j", as LAME defaults to the specified value (joint stereo) when using --vbr-new (see above);
    • drops "-q 0", as LAME defaults to this behaviour when using VBR;
    • drops "-s 44.1", as LAME detects the proper sample rate to use;
    • adds "--noreplaygain" (personal preference);
  • and uses LAME to write tags instead of the id3 package, which has the dual advantage of removing the need for an additional package in the tool chain and allowing the script to write both id3v1 and id3v2 tags (the id3 package does not support id3v2 tags).

Now for the script:

#! /bin/sh

for a in *.flac; do
    OUTF=${a%.flac}.mp3

    ARTIST=`metaflac "$a" --show-tag=ARTIST | sed s/.*=//g`
    TITLE=`metaflac "$a" --show-tag=TITLE | sed s/.*=//g`
    ALBUM=`metaflac "$a" --show-tag=ALBUM | sed s/.*=//g`
    GENRE=`metaflac "$a" --show-tag=GENRE | sed s/.*=//g`
    TRACKNUMBER=`metaflac "$a" --show-tag=TRACKNUMBER | sed s/.*=//g`
    DATE=`metaflac "$a" --show-tag=DATE | sed s/.*=//g`

    flac -c -d "$a" | lame --noreplaygain -V0 \
        --add-id3v2 --pad-id3v2 --ignore-tag-errors --tt "$TITLE" --tn "${TRACKNUMBER:-0}" \
        --ta "$ARTIST" --tl "$ALBUM" --ty "$DATE" --tg "${GENRE:-12}" \
        - "$OUTF"
    RESULT=$?
    if [ "$1" ] && [ "$1" = "-d" ] && [ $RESULT -eq 0 ]; then
        rm "$a"
    fi
done

Alternatively, below is a script that will search for all FLAC audio files beyond where the script resides on your filesystem and convert them to MP3; including those pesky filenames with spaces.

#! /bin/bash

find . -type f -name "*.flac" -print0 | while read -d $'\0' a

do
    OUTF=${a%.flac}.mp3

    ARTIST=`metaflac "$a" --show-tag=ARTIST | sed s/.*=//g`
    TITLE=`metaflac "$a" --show-tag=TITLE | sed s/.*=//g`
    ALBUM=`metaflac "$a" --show-tag=ALBUM | sed s/.*=//g`
    GENRE=`metaflac "$a" --show-tag=GENRE | sed s/.*=//g`
    TRACKNUMBER=`metaflac "$a" --show-tag=TRACKNUMBER | sed s/.*=//g`
    DATE=`metaflac "$a" --show-tag=DATE | sed s/.*=//g`

    flac -c -d "$a" | lame -m j -q 0 --vbr-new -V 0 -s 44.1 - "$OUTF"
    id3 -t "$TITLE" -T "${TRACKNUMBER:-0}" -a "$ARTIST" -A "$ALBUM" -y "$DATE" -g "${GENRE:-12}" "$OUTF"
done

Save the script as flac2mp3 and make the script executable:

chmod a+x flac2mp3

As root, copy the script to /usr/local/bin (or anywhere else that is in your $PATH).

cp flac2mp3 /usr/local/bin

To make /usr/local/bin in your $PATH, do (as normal user):

PATH=$PATH:/usr/local/bin/

and then (as normal user):

nano .bashrc

and add export PATH=$PATH:/usr/local/bin/

Usage

Open up a terminal and cd to the directory of .flac files that you wish to convert and enter flac2mp3

You'll see the verbose decoding/encoding process in the terminal which may take a few moments.

Done.

Addendum

With a small modification the command file can be used to transcode the files into a new directory structure:

#! /bin/bash
find "$1" -name *.flac -print0 | while read -d $'\0' IF
do
  OF=$(echo "$IF" | sed -e 's/\.flac$/.mp3/g' -e "s,$1,$2,g")
  echo "$IF -> $OF"
  mkdir -p "${OF%/*}"

  ARTIST=`metaflac "$IF" --show-tag=ARTIST | sed s/.*=//g`
  TITLE=`metaflac "$IF" --show-tag=TITLE | sed s/.*=//g`
  ALBUM=`metaflac "$IF" --show-tag=ALBUM | sed s/.*=//g`
  GENRE=`metaflac "$IF" --show-tag=GENRE | sed s/.*=//g`
  TRACKNUMBER=`metaflac "$IF" --show-tag=TRACKNUMBER | sed s/.*=//g`
  DATE=`metaflac "$IF" --show-tag=DATE | sed s/.*=//g`

  flac -c -d "$IF" 2> /dev/null | lame -m j -q 0 --vbr-new -V 0 -s 44.1 - "$OF" 2> /dev/null
  id3 -t "$TITLE" -T "${TRACKNUMBER:-0}" -a "$ARTIST" -A "$ALBUM" -y "$DATE" -g "${GENRE:-12}" "$OF"
done

if saved in flac2mp3 this can be used as follows

./flac2mp3 /srv/media/music /srv/media/music-lofi

which will take the directory structure under /srv/media/music and transcode its content into /srv/media/music-lofi.

With some more tweaks the script will support directories that contain '.' (dots) somewhere in the path and executing the script from folders that contain 'flac' files

Also made specifying an alternate folder location optional

#! /bin/bash
find "$1" -name "*.flac" -print0 | while read -d $'\0' IF
do
  if [ "$2" != "" ]
  then
     OF="${IF%.flac}.mp3"
     OF="$2/${OF##*/}"
  else
     OF="${IF%.flac}.mp3"
  fi
  echo "$IF -> $OF"
  mkdir -p "${OF%/*}"

  ARTIST=`metaflac "$IF" --show-tag=ARTIST | sed s/.*=//g`
  TITLE=`metaflac "$IF" --show-tag=TITLE | sed s/.*=//g`
  ALBUM=`metaflac "$IF" --show-tag=ALBUM | sed s/.*=//g`
  GENRE=`metaflac "$IF" --show-tag=GENRE | sed s/.*=//g`
  TRACKNUMBER=`metaflac "$IF" --show-tag=TRACKNUMBER | sed s/.*=//g`
  DATE=`metaflac "$IF" --show-tag=DATE | sed s/.*=//g`

  flac -c -d "$IF" 2> /dev/null | lame -m j -q 0 --vbr-new -V 0 -s 44.1 - "$OF" 2> /dev/null
  id3 -t "$TITLE" -T "${TRACKNUMBER:-0}" -a "$ARTIST" -A "$ALBUM" -y "$DATE" -g "${GENRE:-12}" "$OF"
done

if saved in flac2mp3 this can be used as follows

./flac2mp3 /srv/media.store/music /srv/media/music-lofi

or

./flac2mp3 /srv/media.store/music 

Packages

  • whatmp3AUR A small Python script that accepts a list of directories containing FLAC files as arguments and converts them to MP3 with the specified options.
  • flac2allAUR Audio converter of FLAC to either Ogg Vorbis or MP3 retaining all tags and metadata
  • flac2mp3-bashAUR Bash script to convert Flac to Mp3 easily

Related Links