Ardour Source-Tree layout (Feb 2022)

===== Front Ends =====

gtk2_ardour/
 The main Ardour GUI -- This is where most of the complexity is :)
 It is cleanly separated from the backend and processing engine.

headless/
 hardour -- headless Ardour, mostly demo-code how to use Ardour without a GUI.

session_utils/
 command-line tools using libardour (e.g. export)

luasession/
 arlua -- commandline interface to libardour

===== LIBRARIES =====
 A collection of libraries and utility functions. While most are shared
 libraries, and almost all are exclusive to Ardour.

libs/

 **** Independent, standalone libs ****

 - libs/appleutility/
   Utility Classes, abstraction for CoreAudio and AudioUnits (OSX, macOS)

 - libs/ardouralsautil/
   Utility Class for device-listing (used by the jack and  ALSA backends).
   Device-reservation commandline tool (linked against libdbus), which is
   also available from https://github.com/x42/alsa_request_device

 - libs/clearlooks-newer/
   GTK theme engine (used by gtk2_ardour)

 - libs/fluidsynth/
   Stripped down (library only) and slightly customized version of fluidsynth
   use  tools/update_fluidsynth.sh to update from upstream

 - libs/hidapi/
   Unmodified https://github.com/signal11/hidapi for interaction with some
   control surfaces (Push2, NI Maschine)

 - libs/libltc/
   Unmodified https://github.com/x42/libltc/ for Linear Timecode en/decoding

 - libs/lua/
   Lua Script interpreter and C++ class abstraction
   - libs/lua/lua-5.3.5 is unmodified upstream Lua-5.3.5
   - libs/lua/LuaBridge is a highly customized version of
     https://github.com/vinniefalco/LuaBridge (C++ bindings)

 - libs/midi++2/
   (uses libpdb)
   MIDI parsing, MIDNAM handling, Port abstraction for I/O

 - libs/ptformat/
   Unmodified https://github.com/zamaudio/ptformat for loading ProTools sessions

 - libs/temporal
   various utility code for dealing with different kinds of time,
   including Timecode (FPS) and musical time conversions

 - libs/qm-dsp/
   Stripped down version of https://github.com/c4dm/qm-dsp
   The Queen Mary DSP library is used by VAMP Plugins

 - vamp-plugins
   VAMP plugins for audio analysis and offline processing (uses qm-dsp)

 - libs/vamp-pyin/
   VAMP plugins for pitch and note-tracking (uses qm-dsp), offline analysis

 - libs/vfork/
   A exec-wrapper which redirects file-descriptors to be used with vfork(2)

 - libs/vst3/
   Stripped down version of Steinberg's VST3 SDK
   https://github.com/steinbergmedia/vst3sdk/
   see also tools/update_vst3.sh

 - libs/plugins/
   LV2 Plugins included with Ardour. These are currently mostly
   independent (a-fluidsynth uses libfluidsynth).
   Most of them are custom version of existing plugins (zamaudio, x42),
   that have been customized to be bundled with Ardour on all platforms
   that ardour runs on.

 - libs/zita-convolver/
   convolution kernel, so far only available to Lua scripts.

 - libs/zita-resampler/
   Efficient resampler with variable rate, useful for adaptive resampling.
   Mainly used for vari-speed playback.

 **** PBD dependent libs ****

 - libs/pbd/
   Generic non-Ardour-specific utility classes. This is the basis for all Ardour specifics.
   It provides basic concepts and OS abstractions. The name comes from "Paul
   Barton-Davis", Paul's full name at the time he started working on working on
   audio software.

 - libs/evoral/
   (uses libpbd)
   Control events, control lists, automation evaluation,
   parameter descriptions, incl MIDI event abstraction

   - libs/evoral/libsmf/ (contains several non-upstreamed fixes)
     (used inside evoral)
     Handling Standard MIDI File format. Abstracted to C++ in SMF.{cc,h}
 
 - libs/backends/
   (uses libpdb, ardouralsautil | appleutility, implements libardour interface)
   Interaction with Operating System's Audio/MIDI API:
   ALSA, CoreAudio, JACK, PortAudio/ASIO, Pulseaudio

 - libs/surfaces/
   (uses libpbd, libevoral, libtimecode, libardour ;; libgtkmm2ext, libcanvas)
   Control Surfaces, dynamically loaded by libardour on runtime,
   to remote-control ardour (midi bindings, network etc).

 - libs/panners/
   (uses libpdb, implements libardour interface)
   Pan plugins (stereo-balance, VBAP, etc) are dynamically loaded at runtime.

 - libs/audiographer/
   (uses libpdb)
   Mini Ardour inside Ardour to export audio-files from sessions.

 - libs/ardour/
   (uses pretty much all the libs above)
   This is it. libardour runs Ardour sessions
   All realtime processing happens here, plugins are managed etc.

 **** Plugin Scan Tools ****

 - libs/auscan/
   Apple Audio Unit Plugin Scan commandline tool.

 - libs/fst/
   VST2/3 plugin scan commandline tool.


 **** UI related libs ****

 - libs/gtkmm2ext/
   (uses libpbd)
   Utility Library to extend GDK, GTK, and basic abstraction for UIs
   and event-loops. This library is not limited to the GUI, but also
   used for other graphical interfaces (e.g. Push2, NI Maschine control
   surfaces).

 - libs/canvas/
   (uses libpbd, libgtkmm2ext)
   Cairo Canvas, provides a slate for scalable drawing and basic layout/packing
  This is used by gtk2ardour's main editor.

 - libs/widgets/
   (uses libpbd, libgtkmm2ext ;; libcanvas utils/colors)
   Ardour GUI widgets (buttons, fader, knobs, etc)

 - libs/waveview/
   (uses libpbd, libgtkmm2ext, canvas,  libardour)
   Threaded waveform rendering and waveform image cache


===== RESOURCE FILES =====
These are bundled as-is.

share/export/
 Export Presets

share/mcp/
 Mackie control surface device files

share/midi_maps/
 Generic MIDI control surface presets

share/osc/
 Configuration presets for the OSC control surface

share/patchfiles/
 MIDNAM files, MIDI synth descriptions (note-names, CC, PGM names)

share/scripts/
 Lua scripts (files with a leading underscore are not bundled)
 see also share/scripts/README

share/templates/
 Session templates (currently none)


===== MISC =====
doc/
 Misc developer oriented documentation files and Doxygen

patches/
 Some .diff files for the build-stack.

tools/
 Various developer tools, most notably packaging scripts