Ruby script to convert *.flac to *.mp3 with ffmpeg in Windows

flac_to_mp3.rb

output_dir = "output"

if File.exists? output_dir
        id = 1
	while File.exists?(output_dir + id.to_s) && id < 10
		id += 1
	end
	if id >= 10
		puts "error: can't figure out new output directory name"
		exit 0
	end
	output_dir = output_dir + id.to_s
end

Dir.mkdir output_dir

Dir.glob("*.flac").each do | file |
	puts "processing '#{file}'"
	file.gsub! /\.flac/, ''
	cmd = 'C:/cmd/ffmpeg/bin/ffmpeg -v 1 -i "' + file + '".flac -f mp3 -b:a 320k "' + output_dir + "/" + file + '.mp3"'
	puts "	command: " + cmd
	if not system(cmd)
		puts "	error"
	else
		puts "	done."
	end
end

Variant for conversion of m4a to mp3 at Ubuntu:

#! /usr/bin/ruby

# @ubuntu: depends on ffmpeg, libavcodec-extra-53

output_dir = "output"

if File.exists? output_dir
    id = 1
    while File.exists?(output_dir + id.to_s) && id < 10
        id += 1
    end
    if id >= 10
        puts "error: can't figure out new output directory name"
        exit 0
    end
    output_dir = output_dir + id.to_s
end

Dir.mkdir output_dir

Dir.glob("*.m4a").each do | file |
    puts "processing '#{file}'"
    file.gsub! /\.m4a/, ''
    cmd = 'ffmpeg -v 1 -i "' + file + '".m4a -f mp3 -b:a 320k "' + output_dir + "/" + file + '.mp3"'
    puts " command: " + cmd
    if not system(cmd)
        puts " error"
    else
        puts " done."
    end
end

Variant in Bash:

#! /bin/bash

OUTPUT_DIR="ffmpeg_output"
mkdir -p $OUTPUT_DIR

for flac in *.flac
do
    mp3=$(echo $flac | sed s/flac/mp3/)
    ffmpeg -i "$flac" -f mp3 -b:a 320k "$OUTPUT_DIR/$mp3"
 done