Convert all .ape files to .flac in different subfolders

The command that you need is:

find /path/to/MainDir/ -type f -name "*.ape"  -execdir sh -c ' avconv -i "$1" "${1%.ape}.flac" ' _ {} \;

This will find each file that has .ape suffix and then convert it with the same filename with .flac suffix to the same location as original file is located.

{} is the path of current found file.
_{See the test from here}

The (python) script below should do the job. Copy it into an empty file, save it as convert.py, set the directory to the files in the head section of the script (convert_dir =) and run it by the command:

python3 /path/to/convert.py

The script

#!/usr/bin/env python3

convert_dir = "/path/to/folder/tobeconverted"

import os
import subprocess

for root, dirs, files in os.walk(convert_dir):
    for name in files:
        if name.endswith(".ape"):
            # filepath+name
            file = root+"/"+name
            # to use in other (convert) commands: replace the "avconv -i" by your command, and;
            # replace (".ape", ".flac") by the input / output extensions of your conversion
            command = "avconv -i"+" "+file+" "+file.replace(".ape", ".flac")
            subprocess.Popen(["/bin/bash", "-c", command])
        else:
            pass

Now that ffmpeg is preferred over avconv again, and there are cheap many core computers ($60 for an 8 core XU4) I fount the following to be most effective;

#!/bin/bash

#
# ape2flac.sh
#

function f2m(){
        FILE=$(echo "$1" | perl -p -e 's/.ape$//g');
        if [ ! -f "$FILE".flac ] ; then
                ffmpeg -v quiet -i "$FILE.ape" "$FILE.flac"
        fi
}
export -f f2m
find "$FOLDER" -name '*.ape' | xargs -I {} -P $(nproc) bash -c 'f2m "$@"' _ "{}"