add convert.sh

examples/voxceleb/sv0/local/convert.sh

+# copy this to root directory of data and 
+# chmod a+x convert.sh
+# ./convert.sh
+# https://unix.stackexchange.com/questions/103920/parallelize-a-bash-for-loop
+dir=$1
+open_sem(){
+    mkfifo pipe-$$
+    exec 3<>pipe-$$
+    rm pipe-$$
+    local i=$1
+    for((;i>0;i--)); do
+        printf %s 000 >&3
+    done
+}
+run_with_lock(){
+    local x
+    read -u 3 -n 3 x && ((0==x)) || exit $x
+    (
+     ( "$@"; )
+    printf '%.3d' $? >&3
+    )&
+}
+N=32 # number of vCPU
+open_sem $N
+for f in $(find ${dir} -name "*.m4a"); do
+    run_with_lock ffmpeg -loglevel panic -i "$f" -ar 16000 "${f%.*}.wav"
+done