added documentation

README.md

@@ -3,3 +3,5 @@ This is an automatic movie subtitle synchronization tool.
 Synchronization is done by listening to the audio track, translating it if necessary.
 
 For more information see [https://sc0ty.github.io/subsync](https://sc0ty.github.io/subsync)
+
+[Documentation](doc/index.md)

doc/architecture.md

@@ -0,0 +1,12 @@
+# SubSync architecture overview
+SubSync is composed of two main modules:
+- main module written in Python;
+- _gizmo_ written in C++ and compiled to Python binary module.
+
+Main module is responsible for displaying GUI, asset downloading and installation and contains business logic, whereas gizmo is doing heavy lifting such as speech recognition, audio and subtitle extraction and synchronization.
+
+## Main module
+Written in Python (3.5 or never).
+
+## Gizmo
+Written in C++11 with [pybind11](https://github.com/pybind/pybind11), compiled as Python binary module. Uses [ffmpeg](https://ffmpeg.org) libraries for media extraction and [pocketsphinx](https://cmusphinx.github.io) for speech recognition.

doc/index.md

@@ -0,0 +1,6 @@
+# Documentation
+See also [https://sc0ty.github.io/subsync](https://sc0ty.github.io/subsync).
+
+## Topics
+1. [Architecture overview](architecture.md)
+2. [Compilation](install.md)

doc/install.md

@@ -0,0 +1,70 @@
+# SubSync installation
+You could download release builds from [download page](https://sc0ty.github.io/subsync/en/download.html).
+
+Building SubSync is two step process. First you need to build _gizmo_ module (in folder `gizmo`), then you could build (or run under interpreter) SubSync itself.
+There are several ways to build and run SubSync, it is due to significant differences in supported platforms.
+
+## Prerequisites
+For _gizmo_ module:
+- C++11 compatible compiler (or better C++14);
+- pybind11;
+- ffmpeg libraries (4.0 or newer);
+- sphinxbase and pocketsphinx.
+
+For main module:
+- Python interpreter (supporting Python 3.5 or newer);
+- Python modules listed in `requirements.txt` file;
+- compiled _gizmo_ module.
+
+## POSIX platforms
+For POSIX compatibile platforms (e.g. Linux), standard Python `setup.py` scripts are provided.
+
+It is advised to build under Python virtualenv. To do that, go to project main directory and type:
+```
+pip install virtualenv
+virtualenv venv
+```
+You could also specify different version of Python interpreter, for details see [the docs](https://docs.python-guide.org/dev/virtualenvs/#lower-level-virtualenv).
+
+Then activate your virtualenv and install required packages:
+```
+source venv/bin/activate
+pip install -r requirements.txt
+```
+
+If you have ffmpeg, sphinxbase and pocketsphinx libraries installed and avaiable via `pkg-config`, you could now build _gizmo_:
+```
+cd gizmo
+python setup.py build
+```
+
+If you don't want to use `pkg-config` (or you can't), you must provide paths to these libraries manually using following options:
+```
+--ffmpeg-dir=PATH
+--sphinxbase-dir=PATH
+--pocketsphinx-dir=PATH
+--use-pkg-config=yes|no
+```
+Or env variables:
+```
+FFMPEG_DIR=PATH
+SPHINXBASE_DIR=PATH
+POCKETSPHINX_DIR=PATH
+USE_PKG_CONFIG=yes|no
+```
+
+And then install it under virtualenv, e.g.:
+```
+export FFMPEG_DIR=~/projects/ffmpeg
+export SPHINXBASE_DIR=~/projects/sphinxbase
+export POCKETSPHINX_DIR=~/projects/pocketsphinx
+export USE_PKG_CONFIG=no
+python setup.py build
+python setup.py install
+
+```
+
+Now you could run SubSync from your virtualenv
+```
+python subsync.py
+```