[DOC] start doc might be OK

doc/tutorial/002_Write.bb

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+
+=== Objectif ===
+:** Understand write audio stream
+
+=== sample source: ===
+	[[http://github.com/HeeroYui/river.git/sample/write/ | sample source]]
+
+=== Bases: ===
+
+The writing work nearly like the read turoral. Then we will just see what has change.
+
+==== File configuration: ====
+
+[code style=c++]
+static const std::string configurationRiver =
+		"{\n"
+		"	speaker:{\n"
+		"		io:'output',\n"
+		"		map-on:{\n"
+		"			interface:'auto',\n"
+		"			name:'default',\n"
+		"		},\n"
+		"		frequency:0,\n"
+		"		channel-map:['front-left', 'front-right'],\n"
+		"		type:'auto',\n"
+		"		nb-chunk:1024,\n"
+		"		volume-name:'MASTER'\n"
+		"	}\n"
+		"}\n";
+[/code]
+
+==== Create your write interface: ====
+
+[code style=c++]
+// create interface:
+std11::shared_ptr<river::Interface> interface;
+//Get the generic input:
+interface = manager->createOutput(48000,
+                                  std::vector<audio::channel>(),
+                                  audio::format_int16,
+                                  "speaker");
+[/code]
+
+Here we create an interface with:
+:** The frequency of 48000 Hz.
+:** The default Low level definition channel
+:** A data interface of 16 bits samples coded in [-32768..32767]
+:** Select input interaface name "speaker"
+
+
+==== write datas: ====
+
+The best way to get data is to instanciate a simple callback.
+The callback is called when sample are needed and you have the nbChunk/frequency
+to generate the data, otherwise you can generate error in data stream.
+
+
+[code style=c++]
+// set callback mode ...
+interface->setOutputCallback(std11::bind(&onDataNeeded,
+                                         std11::placeholders::_1,
+                                         std11::placeholders::_2,
+                                         std11::placeholders::_3,
+                                         std11::placeholders::_4,
+                                         std11::placeholders::_5,
+                                         std11::placeholders::_6));
+[/code]
+
+==== Callback inplementation: ====
+
+Simply declare your function and do what you want inside.
+
+[code style=c++]
+void onDataNeeded(void* _data,
+                  const std11::chrono::system_clock::time_point& _time,
+                  size_t _nbChunk,
+                  enum audio::format _format,
+                  uint32_t _frequency,
+                  const std::vector<audio::channel>& _map) {
+	if (_format == audio::format_int16) {
+		// stuff here
+	}
+}
+[/code]