Updated Configure the cameras (markdown)

Configure-the-cameras.md

@@ -1,6 +1,6 @@
 Please read [Build and install](https://github.com/webcamoid/akvirtualcamera/wiki/Build-and-install) page before going further.
 
-## Quick rundown
+# Quick rundown
 
 The first step to create a virtual camera is defining a virtual device:
 
@@ -27,6 +27,7 @@ For example:
 AkVCamManager add-format AkVCamVideoDevice0 YUY2 640 480 30
 ```
 
+First format defined is the default frame format.  
 You can list all capture formats with:
 
 ```
@@ -42,7 +43,7 @@ AkVCamManager update
 
 **Note**: You must run an update every time you modify any parameter of the virtual camera. Also **NEVER** modify the virtual camera parameters when a client is running it.
 
-## Managing the devices
+# Managing the devices
 
 List all devices:
 
@@ -74,7 +75,7 @@ Or get the device description with:
 AkVCamManager description AkVCamVideoDevice0
 ```
 
-## Managing the formats
+# Managing the formats
 
 List all formats:
 
@@ -106,7 +107,7 @@ You can get the default recommended output format with:
 AkVCamManager default-format --output
 ```
 
-## No signal picture
+# No signal picture
 
 When a client program try to play the virtual camera but it isn't receiving any frame, it will show a random dot pattern, you can change it to show a custom picture instead with:
 
@@ -126,10 +127,74 @@ You must give a full path to a picture file, the supported formats for the pictu
 * JPG
 * PNG
 
-## Loading configurations from a file
+# Loading configurations from a file
 
-**In-progress**
+Alternatively, you can define and configure all virtual devices at once using an INI file like.  
+The INI file follows [QSettings file format](https://doc.qt.io/qt-5/qsettings.html).  
+Once you have finished writing your settings file, you can pass it to the manager as:
 
 ```
 AkVCamManager load settings.ini
 ```
+
+You don't need to call **update** because **load** will automatically call it for you.  
+Before continue, let make it clear that the order of the sections (those enclosed between **[ ]**) or it's fields (those lines in the form of **key = value**) does not matters, we are just putting it in natural order to make it easier to understand.  
+
+## Defining the devices
+
+Following is the code for defining the devices:
+
+```
+[Cameras]
+cameras/size = 2
+
+cameras/1/description = My Virtual Camera
+cameras/1/formats = 1
+
+cameras/2/description = My Other Virtual Camera
+cameras/2/formats = 1, 2
+```
+
+First at all you must create a _[Cameras]_ section and set the number of webcams that will be defined with _cameras/size_, cameras indexes starts with 1. Each camera has the following properties:
+
+* **description**: The description that will shown to the capture or streaming program.
+* **formats**:  is a comma separated list of index of formats supported by the device, we will talk about this in a moment.
+
+## Defining the formats
+
+Next step is defining the formats:
+
+```
+[Formats]
+formats/size = 2
+
+formats/1/format = YUY2
+formats/1/width = 640
+formats/1/height = 480
+formats/1/fps = 30
+
+formats/2/format = RGB24, YUY2
+formats/2/width = 640
+formats/2/height = 480
+formats/2/fps = 20/1, 15/2
+```
+
+**format** can be set to any pixel format we been talk before, then set the frame resolution with **width** and **height**, **fps** sets the frame rate and it can be either a positive integer number or a positive fraction in the form **numerator/denominator**.  
+
+You may be noted that the second format has comma separated values, this is because you can actually define many formats with similar properties at once with just a minimal number of lines. The driver will combine the values, so for format 2 in this example you get the following formats:
+
+* RGB24 640x480 20  FPS
+* RGB24 640x480 7.5 FPS
+* YUY2  640x480 20  FPS
+* YUY2  640x480 7.5 FPS
+
+If you want a good compatibility with many capture programs you must provide at least the YUY2 640x480 format in your devices. 
+
+## No signal picture
+
+You must add the following lines to the settings file for setting the place holder picture:
+
+```
+[General]
+default_frame = /path/to/place_holder_picture.png
+```