audio: rewrote audio cache to write to contiguous segments rather than one long file

Fixes issues with PCM file placement, optimizes some audio-based timeline
and cache operations, just generally a better approach.

app/codec/encoder.cpp

@@ -20,6 +20,8 @@
 
 #include "encoder.h"
 
+#include <QFile>
+
 #include "ffmpeg/ffmpegencoder.h"
 
 OLIVE_NAMESPACE_ENTER
@@ -34,6 +36,12 @@ const EncodingParams &Encoder::params() const
   return params_;
 }
 
+void Encoder::WriteAudio(AudioParams pcm_info, const QString &pcm_filename)
+{
+  QFile f(pcm_filename);
+  WriteAudio(pcm_info, &f);
+}
+
 EncodingParams::EncodingParams() :
   video_enabled_(false),
   video_bit_rate_(0),