while loop is running only once?

I am trying to make a clip out of video file by playing it only for certain interval.

make_mclip.sh

#!/bin/bash

mediafile=$@
mediafile_fullpath=$PWD/./$mediafile
tmpedlfile=$(mktemp)

mplayer -edlout $tmpedlfile "$mediafile" &> /dev/null

cat $tmpedlfile | while read f
do
    startpos=$(echo $f | awk '{print $1}')
    endpos=$(echo $f | awk '{print $2}')
    length=$(echo "$endpos-$startpos" | bc)

    tmpclip=$(mktemp --suffix='.mclip' --tmpdir=$PWD)
    echo -e "$mediafile_fullpath\t$startpos\t$length" > $tmpclip

    mplayer_clip.sh "$tmpclip" &>/dev/null

    echo -n "clip name : "
    read clipname < /dev/tty

    mv -nv "$tmpclip" "$clipname.mclip"
done

echo doing rm "$tmpedlfile"

mplayer_mclip.sh

#!/bin/bash

mediafile=$(cat "$@" | awk -F'\t' '{print $1}')
startpos=$(cat "$@" | awk -F'\t' '{print $2}')
length=$(cat "$@" | awk -F'\t' '{print $3}')

mplayer -ss $startpos -endpos $length "$mediafile" &> /dev/null

But for some reason the while loop in make_mclip.sh is only run once even if $tempedlfile contains more than one line; the only exception is if the line

    mplayer_clip.sh "$tmpclip" &>/dev/null

is removed.

Whats wrong ?

ps. I would also like to know if there is already a program for this .