chocolatey install

Many open-source projects can be easily installed on Windows using chocolatey - and it's scriptable, too. Installing chocolatey itself took a few steps.

I should have done with this,

https://docs.chocolatey.org/en-us/choco/setup/#installing-chocolatey-cli

but I ended up doing the powershell install,

https://docs.chocolatey.org/en-us/choco/setup/#install-with-powershellexe

So, running powershell as administrator, checking powershell version with

$PSVersionTable

(it was v5, so chocolatey is supported) and then  

Get-ExecutionPolicy

returned Restricted, so then ran 

Set-ExecutionPolicy AllSigned

and then the install script with

Set-ExecutionPolicy Bypass -Scope Process -Force; [System.Net.ServicePointManager]::SecurityProtocol = [System.Net.ServicePointManager]::SecurityProtocol -bor 3072; iex ((New-Object System.Net.WebClient).DownloadString('https://community.chocolatey.org/install.ps1'))

Opening a cmd window (as administrator) after this, and 

choco install ffmpeg 

worked fine.