Any beat detection software for Linux?

At the site DaveParillo suggested I've found BpmDj project. It has a bpmcount executable that calculates the bpm very nice: it handles mp3 as well as flac:

161.135 Metallica/2008 - Death Magnetic/01-That Was Just Your Life.flac
63.5645 Doom3.mp3

The only thing that's left is to retag the collection. I'll update this answer whenever I succeed. Thanks! :)

---

Step 1

Run bpmcount against the entire collection and store the results into a textfile. The problem is that bpmcount crashes from time to time and tries to eat up to 2GB of memory when it processes several files so we should feed it with filenames one by one. Like this:

musicdir='/home/ootync/music'
find "$musicdir" -iregex ".*\.\(mp3\|ogg\|flac\|ape\)" -exec bpmcount {} \; \
    | fgrep "$musicdir" > "$musicdir/BPMs.txt"

---

Step 2

We'll need some additional packages: apt-get install vorbis-tools flac python-mutagen. Now have a look at how the 'bpm' tag can be added:

mid3v2 --TBPM 100 doom3.mp3
vorbiscomment -a -t "BPM=100" mother.ogg
metaflac --set-tag="BPM=100" metallica.flac

Alas, I have no *.ape tracks

Now we have the BPMs and the entire collection should be retagged. Here's the script:

cat "$musicdir/BPMs.txt" | while read bpm file ; do
    bpm=`printf "%.0f" "$bpm"` ;
    case "$file" in 
        *.mp3) mid3v2 --TBPM "$bpm" "$file" > /dev/null ;; 
        *.ogg) vorbiscomment -a -t "BPM=$bpm" "$file" ;; 
        *.flac) metaflac --set-tag="BPM=$bpm" "$file" ;; 
        esac
    done

---

Step 2.1 Revisited Here's a script that will add BPM tags to your collection.

It runs one process per CPU Core to make the process faster. Additionally, it uses no temporary files and it capable of detecting whether a file is already tagged.

Additionally, I've discovered that FLAC sometimes has both ID3 and VorbisComment inside. This script updates both.

#!/bin/bash

function display_help() {
    cat <<-HELP
            Recursive BPM-writer for multicore CPUs.
            It analyzes BPMs of every media file and writes a correct tag there.
            Usage: $(basename "$0") path [...]
            HELP
    exit 0
    }

[ $# -lt 1 ] && display_help

#=== Requirements
requires="bpmcount mid3v2 vorbiscomment metaflac"
which $requires > /dev/null || { echo "E: These binaries are required: $requires" >&2 ; exit 1; }

#=== Functions

function bpm_read(){
    local file="$1"
    local ext="${file##*.}"
    declare -l ext
    # Detect
    { case "$ext" in
        'mp3')  mid3v2 -l "$file" ;;
        'ogg')  vorbiscomment -l "$file" ;;
        'flac') metaflac --export-tags-to=- "$file" ;;
        esac ; } | fgrep 'BPM=' | cut -d'=' -f2
    }
function bpm_write(){
    local file="$1"
    local bpm="${2%%.*}"
    local ext="${file##*.}"
    declare -l ext
    echo "BPM=$bpm @$file"
    # Write
    case "$ext" in
        'mp3')  mid3v2 --TBPM "$bpm" "$file" ;;
        'ogg')  vorbiscomment -a -t "BPM=$bpm" "$file" ;;
        'flac') metaflac --set-tag="BPM=$bpm" "$file"
                mid3v2 --TBPM "$bpm" "$file" # Need to store to ID3 as well :(
                ;;
        esac
    }

#=== Process
function oneThread(){
    local file="$1"
    #=== Check whether there's an existing BPM
        local bpm=$(bpm_read "$file")
        [ "$bpm" != '' ] && return 0 # there's a nonempty BPM tag
    #=== Detect a new BPM
    # Detect a new bpm
    local bpm=$(bpmcount "$file" | grep '^[0-9]' | cut -f1)
    [ "$bpm" == '' ] && { echo "W: Invalid BPM '$bpm' detected @ $file" >&2 ; return 0 ; } # problems
    # Write it
    bpm_write "$file" "${bpm%%.*}" >/dev/null
    }

NUMCPU="$(grep ^processor /proc/cpuinfo | wc -l)"
find $@ -type f -regextype posix-awk -iregex '.*\.(mp3|ogg|flac)' \
    | while read file ; do
        [ `jobs -p | wc -l` -ge $NUMCPU ] && wait
        echo "$file"
        oneThread "$file" &
        done

Enjoy! :)

This is a command-line tool to detect the BPM and put it in the FLAC file tags:

http://www.pogo.org.uk/~mark/bpm-tools/

I used kolypto's original script using bpmcount and rewrote it for bpm-tag (utility of bpm-tools) which I had better luck with installing. I also made some improvements of my own.

You can find it on GitHub https://github.com/meridius/bpmwrap