deus@ubuntu:~/ffmpeg.work$ ll
total 1159144
drwxrwxr-x  2 deus deus      4096 Jan 27 06:53 ./
drwxr-xr-x 32 deus deus      4096 Jan 27 02:44 ../
-rw-rw-r--  1 deus deus 593460333 Jan 27 03:28 test orig.mp4
-rw-rw-r--  1 deus deus 593460333 Jan 27 03:29 test.orig.mp4
-rwxrwx-w-  1 deus deus       251 Jan 27 06:53 test.sh*
deus@ubuntu:~/ffmpeg.work$ cat test.sh
#!/bin/bash

inputfiles=("*.mp4")
outputfiles=("${inputfiles[*]/%.*/.test.mp4}")

echo "Input Files"

for item in ${inputfiles[*]}
do
  printf "  %s\n" "$item"
done

echo "Output Files"
for item in ${outputfiles[*]}
do
  printf "  %s\n" "$item"
done

deus@ubuntu:~/ffmpeg.work$ ./test.sh
Input Files
  test orig.mp4
  test.orig.mp4
Output Files
  *.test.mp4
deus@ubuntu:~/ffmpeg.work$