ffmpegdecoder: added helper functions for memory handling

app/codec/ffmpeg/ffmpegdecoder.cpp

@@ -1007,6 +1007,28 @@ void FFmpegDecoder::CacheFrameToDisk(AVFrame *f)
   }
 }
 
+void FFmpegDecoder::RemoveFirstFromFrameCache()
+{
+  if (cached_frames_.isEmpty()) {
+    return;
+  }
+
+  av_frame_free(&cached_frames_.first());
+  cached_frames_.removeFirst();
+  cache_at_zero_ = false;
+}
+
+void FFmpegDecoder::RemoveLastFromFrameCache()
+{
+  if (cached_frames_.isEmpty()) {
+    return;
+  }
+
+  av_frame_free(&cached_frames_.last());
+  cached_frames_.removeLast();
+  cache_at_eof_ = false;
+}
+
 void FFmpegDecoder::ClearFrameCache()
 {
   for (int i=0;i<cached_frames_.size();i++) {

app/codec/ffmpeg/ffmpegdecoder.h

@@ -104,6 +104,8 @@ private:
 
   void CacheFrameToDisk(AVFrame* f);
 
+  void RemoveFirstFromFrameCache();
+  void RemoveLastFromFrameCache();
   void ClearFrameCache();
 
   AVFormatContext* fmt_ctx_;