MythTV Architecture

pre-0.23

Introduction

Over the last couple years MythTV has grown into a rather large application. The purpose of these pages is to provide a portal into the code for developers to get their heads around it. This is intended for both those new to MythTV and experienced with it to get familiar with different aspects of the code base.

If you are just looking for the code formatting standards, see the official MythTV wiki article coding standards. If you are looking for the bug tracker, it can be found on the official pages. If you haven't already, you should subscribe to the developer mailing list and the SVN commits mailing list

If you just stumbled onto the developer pages by accident, maybe you want to go to the official MythTV Installation page. There is also a good unofficial Fedora MythTV installation page, and a Gentoo MythTV installation page.

If you are new to Qt programming it is essential that you keep in mind that almost all Qt objects are not thread-safe, including QString. Almost all Qt container objects, including QString, make shallow copies on assignment, the two copies of the object must only be used in one thread unless you use a lock on the object. You can use the QDeepCopy template on most Qt containers to make a copy you can use in another thread.

There are some special dangers when using QObject outside the Qt event thread.

There is a short HOWTO on Profiling MythTV available in addition to documentation on the code itself.

There are also a few simple testing shortcuts.

Libraries

MythTV is divided up into 17 libraries:

libmythdb

Lowest-level MythTV library. Used by the Plugins. Contains the database, LCD, and network support code (used by the myth network protocol).

This also contains some other basic functionality and classes which are used by one or more of libmyth, libmythui and libmythtv.

Any changes to this library's ABI may trigger a myth binary version change because the plugins depend on it.

libmythui

Main user interface rendering library. Used by the Plugins. The mouse/touchscreen gesture, remote control (LIRC and AppleRemote) and screen saver control code are also contained in this library.

This library depends on libmyth. Any changes to this library's ABI may trigger a myth binary version change because the plugins depend on it.

libmythupnp

Initial uPnP (universal Plug and Play) support

This library depends on libmythdb.

libmyth

Core MythTV library. Used by the Plugins. The audio, language support, plugin manager, media manager, and some UI widgets are implemented by libmyth.

This library depends on both libmyth, libmythupnp and libmythui. Any changes to this library's ABI may trigger a myth binary version change because the plugins depend on it.

libmythtv

MythTV TV functionality library. Used by some Plugins. The OSD, recorders, video and A/V players are supported by libmythtv.

This library depends on libmythdb, libmythui and libmyth. It also depends on avlib, libmythmpeg2, libmythsamplerate, libmythsoundtouch, libdvdnav, libfreemheg and liblivemedia.

This library is used by some plugins so changes to it's ABI may require a myth binary version change.

Any changes to classes that are serialized by the myth network protocol (for example ProgramInfo) or to the protocol itself require the protocol version number to be incremented.

libavcodec/libavformat/libavutil/libpostproc/libswscale

These together form the FFmpeg A/V decoding library (aka avlib). Documented Externally.

These should be modified as little as possible, and any changes should be sent upstream for inclusion in the FFmpeg project's version of these libraries.

These libraries do not depend on any of our libraries.

libmythmpeg2

Alternate MPEG-1/2 A/V decoding library. External Website.

This is an alternate MPEG-2 decoding library. It is offered as an option for software decoding of MPEG-1 and MPEG-2 files. FFmpeg is still used for decoding MPEG still frames when this library is selected for playback.