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# Convert FLAC to MP3

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This article outlines different ways to transcode from FLAC to MP3. FLAC is a lossless audio format, so it is better for archival purposes, but it also takes up more disk space. The idea is to compress the files without creating a perceived loss in fidelity.

## Packages

- audiotoolsAUR - Transcode between different formats and keep tags with `track2track`, can encode from CDDA with `cdda2track`, has an optional Ncurses GUI.
- flac2allAUR - Multi-threaded conversion of flac to 70+ other formats retaining all tags and metadata.
- 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.

### Graphical applications

- SoundConverter — A dedicated audio transcoding utility built for the GNOME desktop and relying on GStreamer. It can make use of GNOME Audio Profiles and features multithreaded conversions. It can also extract the audio from videos.

  https://soundconverter.org/ || soundconverter

- soundKonverter — A Qt graphical frontend to various audio manipulation programs. Features conversion, ripping and other audio manipulation functionalities.

  https://github.com/HessiJames/soundkonverter/wiki || soundkonverterAUR

- WinFF — A GUI for the powerful multimedia converter FFmpeg. Features dedicated profiles for audio transcoding.

  https://github.com/WinFF/winff/ || winff-gtk3AUR, winff-qt6AUR

## Usage

In these two examples, FLAC files in current directory are encoded by the LAME MP3 encoder. Both scripts pass the ID3 tags from the FLAC files to the resulting MP3 files, and encode to MP3 V0. V0 results in a variable bitrate usually between 220-260 kbps. The audio of a V0 file 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 significantly reduced. For more information on LAME switches/settings such as V0, visit the Hydrogenaudio LAME Wiki.

The original `.flac` files are not modified and the resulting `.mp3`s will be in the same directory. All files with extensions not matching `*.flac` in the working directory (`.nfo`, images, `.sfv`, etc.) are ignored.

For ease of use, add the script to your `PATH`. Open up a terminal, `cd` to the directory of FLAC files that you wish to convert, and invoke `flac2mp3` (or whatever you named the script). You will see the verbose decoding/encoding process in the terminal which may take a few moments. Done! At this point, it is trivial to `mv *.mp3` all your new MP3s wherever you wish.

### With FFmpeg

Chances are, your system already has FFmpeg installed, which brings in the flac and lame packages. FFmpeg has all the encoding and decoding facilities built in to do the job.

    #!/bin/bash

    for a in ./*.flac; do
      < /dev/null ffmpeg -i "$a" -qscale:a 0 "${a[@]/%flac/mp3}"
    done

#### Parallel version

Since LAME is a single-threaded encoder, conversion can be accelerated by encoding multiple files concurrently on multiple cores. To do this, install the parallel package, and run:

    parallel ffmpeg -i {} -qscale:a 0 {.}.mp3 ::: ./*.flac

#### Parallel with recursion

Fd is a fast, user-friendly alternative to find. This one liner avoids the "while read" loop, which may have performance implications according to a response on Stack Exchange. [1]

Install fd first, then run:

    fd -t f -e flac -x ffmpeg -i "{}" -qscale:a 0 "{.}.mp3"

#### Makefile for incremental recursive transcoding

Warning: Makefiles do not handle spaces correctly, see [2] for details.

Besides transcoding in parallel with `make -j$(nproc)`, this has the added benefit of not regenerating transcoded files that already exist on subsequent executions:

    SOURCE_DIR := flacdir
    XCODE_MP3_DIR := mp3dir
    # NOTE: see lame -v option for quality meaning
    XCODE_MP3_QUALITY := 0

    # Find .flac sources and determine corresponding targets
    flac_srcs := $(shell find $(SOURCE_DIR) -type f -name '*.flac')
    flac_2_mp3_tgts := $(patsubst $(SOURCE_DIR)/%.flac, $(XCODE_MP3_DIR)/%.mp3, \
        $(flac_srcs))

    .PHONY: all mp3 flac_2_mp3

    all: mp3

    mp3: flac_2_mp3

    flac_2_mp3: $(flac_2_mp3_tgts)

    $(XCODE_MP3_DIR)/%.mp3: $(SOURCE_DIR)/%.flac
            @echo "converting -> $@"
            @mkdir -p "$(@D)"
            @ffmpeg -v error -i "$<" -codec:a libmp3lame \
                -q:a $(XCODE_MP3_QUALITY) "$(@)"

### Without FFmpeg

If for some reason FFmpeg is not installed and you do not want to install it, you still need to have flac and lame installed. Here, the tagging process is more explicit using the metadata utility that comes with flac and passing the information to lame. The process duration will slightly increase since FLACs must first be decoded to WAVE and then fed into the MP3 encoder.

    #!/bin/bash

    for a in ./*.flac; do
      # give output correct extension
      OUTF="${a[@]/%flac/mp3}"

      # get the tags
      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)

      # stream flac into the lame encoder
      flac -c -d "$a" | lame -V0 --add-id3v2 --pad-id3v2 --ignore-tag-errors \
        --ta "$ARTIST" --tt "$TITLE" --tl "$ALBUM"  --tg "${GENRE:-12}" \
        --tn "${TRACKNUMBER:-0}" --ty "$DATE" - "$OUTF"
    done

### Recursively

A useful extension of the above scripts is to let them recurse into all subdirectories of the working directory. To do so, replace the first line (`for .... do`) with:

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

## See also

- https://www.xiph.org/flac/
- Wikipedia:FLAC
- https://lame.sourceforge.net/
- https://wiki.hydrogenaudio.org/index.php?title=Flac - More information on FLAC.
- CUE Splitting to split a single FLAC with cue sheet into multiple audio files

Category:

- Audio