mencoder -of lavf -lavfopts format=mp4 -oac lavc -ovc lavc -lavcopts aglobal=1:vglobal=1:acodec=libfaac:abitrate=128:vcodec=mpeg4:keyint=25 -ofps 24 -af lavcresample=44100 -vf harddup,scale=320:-3 -mc 0 -noskip film.avi -o film.mp4

#!/bin/bash
if [ $# -eq 0 ]; then
echo -e "USAGE: $(basename $0) avi_files\n\
MP4 files this right tags will be stored in the same dir"
fi
while [ $# -ne 0 ]; do
        if [ "$(echo \"$1\" |xargs file |grep -o AVI)" == "AVI" ] || [ "$(echo \"$1\" |xargs file |grep -o MKV)" == "MKV" ]; then
                fl="$1"
                mp="${1%.[aA][vV][iI]}.mp4"
                answer="Y"
                if  [ -e "$mp" ]; then
                        echo -e "file \"$mp\" Уже существует!!! Заменить? (Y/N)"
                        read answer
                fi
                if [ "$answer" == "y" ] || [ "$answer" == "Y" ]; then
                        mkfifo /tmp/avimp4fifo
                        mencoder -of lavf -lavfopts format=mp4 -oac lavc -ovc lavc -lavcopts aglobal=1:vglobal=1:acodec=libfaac:abitrate=128:vcodec=mpeg4:keyint=25 -ofps 24 -af lavcresample=44100 -vf harddup,scale=320:-3 -mc 0 -noskip "$fl" -o "$mp"

                fi
        else
                echo File: $1 - не AVI файл... пропускаю!!!!
        fi
        shift 1
done