update install instructions for 20.04

README.md

@@ -20,13 +20,54 @@ Install the following packages on Linux:
   * libxinerama-dev
   * libxrandr-dev
 
+Ubuntu 20.04 LTS Support
+------------------------
+
+Azure Kinect isn't officially supported on 20.04
+
+mpdroid's comment on October 17, 2020 seems to indicate that there is a workaround:
+
+https://feedback.azure.com/forums/920053-azure-kinect-dk/suggestions/40368301-support-for-ubuntu-20-04-lts?page=1&per\_page=20
+
+```
+These are the steps I followed to install k4a-tools, libk4a and libk4abt on Ubuntu 20.04. The general steps are as outlined in
+https://docs.microsoft.com/en-us/azure/Kinect-dk/sensor-sdk-download, with a couple of hacks to make things work on 20.04.
+- use of 18.04 repo, even though OS is 20.04
+- installed lower versions of tools and libraries (as latest versions of sensor and body tracker don't seem to be compatible on 20.04)
+
+$ curl -sSL https://packages.microsoft.com/keys/microsoft.asc | sudo apt-key add -
+$ sudo apt-add-repository https://packages.microsoft.com/ubuntu/18.04/prod
+$ curl -sSL https://packages.microsoft.com/config/ubuntu/18.04/prod.list | sudo tee /etc/apt/sources.list.d/microsoft-prod.list
+$ curl -sSL https://packages.microsoft.com/keys/microsoft.asc | sudo apt-key add -
+$ sudo apt-get update
+$ sudo apt install libk4a1.3-dev
+$ sudo apt install libk4abt1.0-dev
+$ sudo apt install k4a-tools=1.3.0
+
+- Verify sensor library by launching camera viewer
+
+$ k4aviewer
+
+- Clone and build [Azure Kinect Samples](https://github.com/microsoft/Azure-Kinect-Samples).
+- Run `simple_3d_viewer` to verify body tracker works.
+```
+
+There will be complaints:
+
+```
+# E: The repository 'https://packages.microsoft.com/ubuntu/18.04/prod focal Release' does not have a Release file.
+# N: Updating from such a repository can't be done securely, and is therefore disabled by default.
+```
+
+Just ignore them.
+
 Webcam
 ------
 
 Update:
 
 This seems to work with some combination of reloading the driver (`./webcam/reload_driver.sh`), running VLC
-(maybe it sets the video buffer mode?), killing firefox, and starting random browsers and going to meet. 
+(maybe it sets the video buffer mode?), killing firefox, and starting random browsers and going to meet.
 Eventually it seems to work.
 
 Docs and software: