Convert MP4 to MP3 on Ubuntu

I keep having to look this kind of thing up, so I think it is better to repost the how-we-did-it's ..
From time to time I find it useful to extract audio (MP3 format) from a video (MP4). My camera takes pretty good video, but a recent how-to video project involved editing several videos, pictures and audio together to make sense of all my ramblings.

In this case, I had video with audio I wanted to use and vice versa and wanted to mix them together .. into a final version video using another program called the  Openshot Video Editor.

my source >> http://magnus-k-karlsson.blogspot.ca/2014/06/convert-mp4-to-mp3-on-ubuntu-1404-trusty.html who posted this quick tip: 

Convert MP4 to MP3 on Ubuntu 14.04 Trusty
There is a program available on Ubuntu youtube-dl, that can download videos from youtube.com or other video platforms. But it stores the file in mp4, since it contains video. But sometimes you do not want the video and only the audio. To extract only the audio part, you can use the pacpl comamnd line tool.

     pacpl --to mp3 -v -r- -bitrate 320 targetfile.mp4

The pacpl program was not installed on my system, as verified by opening a terminal window and typing pacpl .. to which it responded: ..oops, that program is not installed .. try 'sudo apt-get install pacpl' it helpfully suggested .. which I did and it proceeded to install a wonderful long list of utilities re sound and video conversions. Thereafter I was able to use the pacpl command line tool as described by Mr Karlsson above to extract just the audio from most of my video files.

Had I checked, this program was already listed in the Ubuntu Software Center so I could have just searched for it and installed it from there just as I did for the Openshot Video Editor program.