mjhjmtu

A simple 1 liner solution:
find -name "*.flac" -exec ffmpeg -i -acodec libmp3lame -ab 128k .mp3 ;

http://lewisdiamond.blogspot.ca/2012/01/converting-flac-to-mp3.html

Note that this will be applied recursively in the given directory. I.e. if you run this from your Music folder, it will convert all flacs from subfolders and produce a .mp3 next to it. You may also do it without ffmpeg by directly using flac and lame (i.e. read w/ flac, pipe to lame, output to a file .mp3), as shown in the link.

If you have some white spaces in the file names:

for a in *.flac; do
 f="$a[@]/%flac/mp3"
 ffmpeg -i "$a" -qscale:a 0 "$f"
done

I worked on @Ketan's answer using avconv, since ffmpeg doesn't work well over here.

for i in *.flac ; do 
 avconv -i "$i" "./mp3/$i".mp3
done

This converts flac files in a folder into mp3 files and moves then to an existing "mp3" folder. Files will be named in the model "original_name.flac.mp3"

Parallel FTW (no doubt you have more than one core - why not use them?):

ls *flac | while read f; do ffmpeg -i "$f" -acodec libmp3lame $f.mp3 & done

find . -maxdepth 1 -type f -name '*.flac' | while IFS= read -r f; do
 ffmpeg -i "$f" -acodec libmp3lame "$( sed -e's/.flac/.mp3/g' <<< $f )"
done

I took everything I found here (and maybe on some other sites) and created a small tool to not only create mp3s of flacs recursively, but also preserve relative paths to create them elsewhere with multithread support.

oh, and yes, I see, I didn't use ffmpeg in that case, because my OSMC didn't provide packages for ffmpeg, only avconv, but since you're already here, I guess you know, it's "basically" the same - at least for the most important part. Just replace the command "avconv" with "ffmpeg". My first runs were with the ffmpeg bin and the exact same options.

I am by no means a bash hacker, but I managed it, as my first bashscript with the given demands, and maybe someone will benefit.
I am open for any suggestions from your side, but so far it works for me.

my script to spin up the 4 instances, one for each core, is like this:

#!/bin/bash
# this should be quite self-explanatory 
for i in 1..4
do
echo "started instance no: $i"
/home/osmc/transform.sh . &
# sleeping time can be shorter, this is just so, that 
# not all 4 processes will want to start with the same 
# file, during runtime collisions should not become an issue
sleep 5
done
echo "all instances started"

And the worker script like this:

#!/bin/bash
# take care of spaces
IFS=$'n'
# my music folders, remote is the source, local the target dir
remote=/mnt/music/FLAC
local=/mnt/1tb/mp3
# for all flac files start loop
for i in $(find $remote -type f -iname '*.flac' );
do
## SET VARIABLES for PATHS and FILENAMES
## this might be able to be super short with sed and complex one-liner,
## but I s*ck at regex
fullfile=$i
# strip extension
filename="$i##*/"
# add new extension
filename="$filename%.*.mp3"
# get full dirname from inputfile
fulldir=$(dirname "$i")
# strip leading dirs from full input dir
# count the dirs, add two, then you're good.
reldir="$(echo $fulldir | cut -d'/' -f5-)"
# some subdirs in my collection even have a flac subdir, you might
# ignore this, it strips only if it exists
reldir=$reldir//flac
# combine target dir and relative dir
outdir="$local/$reldir"
# generate the full output filename for conversion
outfile="$outdir/$filename"
# create whole target directory - yes, I need it only once, but hey,
# it works, didn't want to start a if not exist statement... should I? 
mkdir -p "$outdir"
# run conversion - finally... you may want or need to replace 
# "avconv" with "ffmpeg"
avconv -n -nostats -loglevel info -i "$fullfile" -codec:a libmp3lame -qscale:a 0 "$outfile"
done

which can be found at
https://github.com/erdnuesse/flac-to-mp3

Regards,
Kay

For example, if you have multiple avi files:

ls *.avi | xargs -I ffmpeg -i .mp3

If it can help ....
I've written a small bash script to do this ....
You need to have ffmpeg / flac installed.

How it works:

It takes 2 arguments :

1. The folder of your music library (flac/ogg/mp3 ...)


2. The destination folder (you need to create it before).

It produce :

• An exact copy from the source folder into the destination folder, with:
  
  
  • the non flac files copied into.
  
  
  • the flac files transformed to mp3 ( VBR high quality)
  
  


• A run.sh file with the commands to convert the flac files (this script is executed automatically).

#!/bin/bash

FLAC_PATH=$1
CONV_PATH=$2

DEBUG=0;

function usage 
 echo "";
 echo " This script convert all flac files from a folder to mp3 files to a second folder";
 echo "";
 echo " Usage :";
 echo " ./conv.sh Source Folder Destination Folder";
 echo " note : booth folder must exist before starting this script";
 echo " files other than flac are copied to the destination folder";
 echo "";


if [ ! -d "$2" ]; then
 echo "";
 echo " ERROR : [$2] is not a directory.";
 usage
 exit 1
fi;

if [ ! -d "$2" ]; then
 echo "";
 echo " ERROR : [$2] is not a directory.";
 usage
 exit 1
fi;

COMMANDS="run.sh"
echo "" > run.sh
echo " convert from $FLAC_PATH to $CONV_PATH ";

find "$FLAC_PATH" -type f |while read myFile; do
 SRC_DIR=$myFile%/*
 SRC_FILE=$myFile##*/
 DST_DIR=$CONV_PATH/$SRC_DIR
 mkdir -p "$DST_DIR"
 # TEST if the file is a flac ....
 metaflac --show-md5sum "$myFile" 2>/dev/null 1>/dev/null
 if [ $? -eq 0 ]; then
 echo -n " *** $myFile [FLAC !] : "
 DST_FILE=$myFile%.*
 OUT_PATH="$DST_DIR/$( echo $SRC_FILE | sed -e 's/.flac$/.mp3/')"

 if [ $DEBUG == 1 ]; then
 echo " SRC = $myFile";
 echo " OUT = $OUT_PATH"
 fi;

 if [ -f "$OUT_PATH" ]; then
 echo " exist, do nothing !";
 else
 echo " add to compress list !";
 echo "ffmpeg -y -i "$myFile" -codec:a libmp3lame -q:a 0 -map_metadata 0 -id3v2_version 3 "$OUT_PATH" " >> $COMMANDS
 fi;

 else
 echo -n " *** $SRC_FILE [NOT FLAC] : "
 if [ -f "$CONV_PATH/$myFile" ]; then
 echo " exist, do nothing !"
 else
 echo " copy."
 cp "$myFile" "$CONV_PATH/$myFile"
 fi
 fi

done;

echo " And now, CONVERT THE FLAC's!!! "
sh run.sh

for a in *.flac

do
OUTF=echo "$a" | sed s/.flac$/.mp3/g

ffmpeg -i "$a" -acodec libmp3lame "$OUTF"

done

To recursively convert in mp3 all the flac or wav files in nested folders, I used this command:

find '~/Music/' -iname '*.flac' , -iname '*.wav' -exec bash -c 'D=$(dirname ""); B=$(basename ""); mkdir "$D/mp3/"; ffmpeg -i "" -ab 320k -map_metadata 0 -id3v2_version 3 -acodec libmp3lame "$D/mp3/$B%.*.mp3"' ;

It will create a folder named "mp3" inside the one with flac or wav files and, inside the mp3 folder, it will save relative mp3 files with a bitrate of 320kbps, without keeping the old file extension in the name.

GNU Parallel is make for these kind of tasks:

# change to the home directory
cd ~/music
# convert all *.flac files
parallel ffmpeg -i -acodec libmp3lame ..mp3 ::: *.flac
# (optional: check whether there are any errors printed on the terminal)
sleep 60

It will run the jobs in parallel (one job per cpu core) and make sure the output on the terminal is not mixed together.

I realize this comes quite late, but for memory, see my script "batchaudiocvt" on sourceforge. It is a (quite large) shell script designed for efficient mass conversion of audio files, between many formats. In particular, it makes its best to convert the usual tags.