Plug-in development guide
Here we will explain how you can create your own plugins for MythTV and share it with the rest of us. Another fast and easy way to get started is by taking a small existing plugin to start with like the MythWeather plug-in.
Step 1: read about the plugin Architecture
First get yourself a little familiar with the MythPlugin Architecture. Don't mind the details, in the next step we have a walk through for your first (Hello world) plugin.
Step 2: Create your first Hello world plugin
Now go to Building Plugins:HelloMyth for a walk through for your first (Hello world) plugin.
This is a really simple skeleton plugin that doesn't do anything. It'll show you what is absolutely necessary to create a plugin, then you can expand on that. After this you can look at existing plugins for more in-depth examples. You can find a list of plugins in the main page.
Step 3: Create a cool new feature for MythTV
Congratulations! you are ready to build your own plugin and get famous forever.
Don't forget to add your new plugin to the Unofficial Plugins section so others can find and use your plugin.
More about coding
For more information about coding in MythTV you can go here