began hybrid indexing system

This index system will have awareness of the disk cache state and be able to
fill in and store frames as necessary while keeping the disk cache under
user defined limits.

app/codec/ffmpeg/ffmpegdecoder.h

@@ -33,6 +33,8 @@ extern "C" {
 #include "codec/decoder.h"
 #include "codec/waveoutput.h"
 
+//#define CACHE_EVERY_FRAME
+
 /**
  * @brief A Decoder derivative that wraps FFmpeg functions as on Olive decoder
  */
@@ -117,6 +119,8 @@ private:
    */
   QString GetConformedFilename(const AudioRenderingParams &params);
 
+  void ValidateIndex();
+
   /**
    * @brief Used internally to load a frame index into frame_index_
    *
@@ -142,11 +146,20 @@ private:
   AVFormatContext* fmt_ctx_;
   AVCodecContext* codec_ctx_;
   AVStream* avstream_;
-  AVDictionary* opts_;
 
   AVPixelFormat ideal_pix_fmt_;
   PixelFormat::Format native_pix_fmt_;
 
+#ifndef CACHE_EVERY_FRAME
+  SwsContext* scale_ctx_;
+
+  AVPacket* pkt_;
+
+  AVFrame* frame_;
+#endif
+
+  AVDictionary* opts_;
+
   QVector<int64_t> frame_index_;
 
 };