[DOC] start doc might be OK

doc/tutorial/004_ConfigurationFile.bb

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+
+=== Objectif ===
+:** Understand the architecture of the configuration file.
+:** all that can be done with it.
+
+
+=== Basis: ===
+
+The river configuration file is a json file. We use [lib[ejson | e-json library]] to parse it then we have some writing facilities.
+
+
+River provide a list a harware interface and virtual interface.
+
+
+The hardware interface are provided by [lib[airtaudio | AirTAudio library]] then we will plug on every platform.
+
+
+The file is simply architecture around a list of object:
+
+[code style=json]
+{
+	"speaker":{
+		
+	},
+	"microphone":{
+		
+	},
+	"mixed-in-out":{
+		
+	},
+}
+[/code]
+
+With this config we declare 3 interfaces : speaker, microphone and mixed-in-out.
+
+
+=== Harware configuration: ===
+
+In every interface we need to define some Element:
+:** "io" :
+:: Can be input/output/... depending of virtual interface...
+:** "map-on": An object to configure airtaudio interface.
+:** "frequency": 0 to automatic select one. Or the frequency to open harware device
+:** "channel-map": List of all channel in the stream:
+::** "front-left"
+::** "front-center"
+::** "front-right"
+::** "rear-left"
+::** "rear-center"
+::** "rear-right"
+::** "surround-left",
+::** "surround-right",
+::** "sub-woofer",
+::** "lfe"
+:** "type": Fomat to open the stream:
+::** "auto": Detect the best type
+::** "int8",
+::** "int8-on-int16",
+::** "int16",
+::** "int16-on-int32",
+::** "int24",
+::** "int32",
+::** "int32-on-int64",
+::** "int64",
+::** "float",
+::** "double"
+:** "nb-chunk": Number of chunk to open the stream.
+
+
+