Add short architecture overview

dev-docs/architecture.md

@@ -7,3 +7,30 @@
   * MVC
   * GUI elements and their counterpart
 * [kdenlivesettings.kcfg](../src/kdenlivesettings.kcfg)
+
+
+## Architectural Overview
+
+Kdenlive uses a number of libraries. The most important library is MLT which is
+responsible for the core video editing functionality: the process of applying
+effects to clips which are organised in tracks and timeline(s). Kdenlive
+provides the user interface for this functionality.
+
+Kdenlive and MLT use a number of resources like frei0r for video effects.
+
+```
+              ┌────────┐   
+              │Kdenlive├─────┐
+              └────┬───┘     │
+    Render projects│         │Configure
+ Decode audio/video│         │effect settings
+                   │         │        
+              ┌────┴───┐     │        
+              │  MLT   ├─────┤             
+              └────────┘     │Audio/Video Effects
+                             ├───────┬──────┬─────────┐
+                          ┌──┴───┐┌──┴───┐┌─┴─┐┌──────┴──────┐
+                          │frei0r││LADSPA││SoX││libsamplerate│
+                          └──────┘└──────┘└───┘└─────────────┘
+```
+<!-- http://marklodato.github.io/js-boxdrawing/ for drawing -->