Problem when downloading software for playing commercial DVD

[Brian]

Ubuntu 16.04 installed and VLC.
Am complete Linux novice.

ProblemType: Package
DistroRelease: Ubuntu 16.04
Package: m4 1.4.17-5
ProcVersionSignature: Ubuntu 4.4.0-127.153-generic 4.4.128
Uname: Linux 4.4.0-127-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.15
AptdaemonVersion: 1.1.1+bzr982-0ubuntu14
Architecture: amd64
Date: Thu May 24 09:57:31 2018
Dependencies:
 gcc-6-base 6.0.1-0ubuntu1
 libc6 2.23-0ubuntu10
 libgcc1 1:6.0.1-0ubuntu1
 libsigsegv2 2.10-4
 multiarch-support 2.23-0ubuntu10
ErrorMessage: package m4 is already installed and configured
InstallationDate: Installed on 2017-07-05 (323 days ago)
InstallationMedia: Ubuntu 16.04.1 LTS "Xenial Xerus" - Release amd64 (20160719)
RelatedPackageVersions:
 dpkg 1.18.4ubuntu1.4
 apt 1.2.26
SourcePackage: dpkg
Title: package m4 1.4.17-5 failed to install/upgrade: package m4 is already installed and configured
UpgradeStatus: No upgrade log present (probably fresh install)