Started implementation of Video Chat (not working yet!).

- GUI part is done
- implemented a very basic JPEG codec
- added echo frame in configuration panel
- created a video capture object that uses OpenCV (should be cross systems)
Remains to do:
- serialise and send frames through p3VoRS
- use a serious codec (e.g. Theora+x264)
- add icons to reflect camera state (failure/working/sending/...)
- compilation on windows 



git-svn-id: http://svn.code.sf.net/p/retroshare/code/trunk@7449 b45a01b8-16f6-495d-af2f-9b41ad6348cc

plugins/VOIP/gui/VideoProcessor.h

@@ -0,0 +1,79 @@
+#pragma once
+
+#include <stdint.h>
+#include <QImage>
+
+class QVideoOutputDevice ;
+
+// This class decodes video from a stream. It keeps a queue of
+// decoded frame that needs to be retrieved using the getNextImage() method.
+//
+class VideoDecoder
+{
+	public:
+		VideoDecoder() { _output_device = NULL ;}
+
+		// Gets the next image to be displayed. Once returned, the image should
+		// be cleared from the incoming queue.
+		//
+		void setDisplayTarget(QVideoOutputDevice *odev) { _output_device = odev ; }
+
+		virtual void receiveEncodedData(const unsigned char *data,uint32_t size) ;
+
+	private:
+		QVideoOutputDevice *_output_device ;
+
+		std::list<QImage> _image_queue ;
+
+		// Incoming data is processed by a video codec and converted into images.
+		//
+		virtual QImage decodeData(const unsigned char *encoded_image,uint32_t encoded_image_size) = 0 ;
+
+		// This buffer accumulated incoming encoded data, until a full packet is obtained,
+		// since the stream might not send images at once. When incoming images are decoded, the
+		// data is removed from the buffer.
+		//
+		unsigned char *buffer ;
+		uint32_t buffer_size ;
+};
+
+// This class encodes video using a video codec (possibly homemade, or based on existing codecs)
+// and produces a data stream that is sent to the network transfer service (e.g. p3VoRs).
+//
+class VideoEncoder
+{
+	public:
+		VideoEncoder() { _echo_output_device = NULL ;}
+
+		// Takes the next image to be encoded. 
+		//
+		virtual bool addImage(const QImage& Image) ;
+
+	protected:
+		//virtual bool sendEncodedData(unsigned char *mem,uint32_t size) = 0 ;
+		virtual void encodeData(const QImage& image) = 0 ;
+
+		unsigned char *buffer ;
+		uint32_t buffer_size ;
+
+		QVideoOutputDevice *_echo_output_device ;
+};
+
+// Now derive various image encoding/decoding algorithms.
+//
+
+class JPEGVideoDecoder: public VideoDecoder
+{
+	protected:
+		virtual QImage decodeData(const unsigned char *encoded_image,uint32_t encoded_image_size) ;
+};
+
+class JPEGVideoEncoder: public VideoEncoder
+{
+	public:
+		JPEGVideoEncoder() {}
+
+	protected:
+		virtual void encodeData(const QImage& Image) ;
+};
+