Refactor encoding/decoding pipeline.

* Add sample format and channels to MediaInfo struct.
* Move MediaInfo, RTPInfo, ProcessorType structs into a single file.
* Abstract audio/video enc/dec from Input/OutputProcessor.
* Abstract basic enc/dec FFmpeg API into Coder class.
* Rename variables to follow cpp code guideline.

erizo/src/erizo/media/ExternalInput.cpp

@@ -184,7 +184,7 @@ void ExternalInput::receiveLoop() {
     AVPacket orig_pkt = avpacket_;
     if (needTranscoding_) {
       if (avpacket_.stream_index == video_stream_index_) {  // packet is video
-        inCodec_.decodeVideo(avpacket_.data, avpacket_.size, decodedBuffer_.get(), bufflen_, &gotDecodedFrame);
+        inCodec_.decodeVideoBuffer(avpacket_.data, avpacket_.size, decodedBuffer_.get(), bufflen_, &gotDecodedFrame);
         RawDataPacket packetR;
         if (gotDecodedFrame) {
           packetR.data = decodedBuffer_.get();

erizo/src/erizo/media/MediaInfo.h

@@ -0,0 +1,36 @@
+#ifndef ERIZO_SRC_ERIZO_MEDIA_MEDIAINFO_H_
+#define ERIZO_SRC_ERIZO_MEDIA_MEDIAINFO_H_
+
+extern "C" {
+#include <libavcodec/avcodec.h>
+}
+
+#include <string>
+#include "codecs/Codecs.h"
+
+namespace erizo {
+
+struct RTPInfo {
+  enum AVCodecID codec;
+  unsigned int ssrc;
+  unsigned int PT;
+};
+
+enum ProcessorType {
+  RTP_ONLY, AVF, PACKAGE_ONLY
+};
+
+struct MediaInfo {
+  std::string url;
+  bool hasVideo;
+  bool hasAudio;
+  ProcessorType processorType;
+  RTPInfo rtpVideoInfo;
+  RTPInfo rtpAudioInfo;
+  VideoCodecInfo videoCodec;
+  AudioCodecInfo audioCodec;
+};
+
+}  // namespace erizo
+
+#endif  // ERIZO_SRC_ERIZO_MEDIA_MEDIAINFO_H_