began audio conform code in ffmpegdecoder

For accuracy, whenever we need to perform an audio resample, we need to do it
in advance. This is in a process called "conforming" and this commit introduces
the framework by which the decoder can automatically conform an audio stream
to arbitrary parameters for accurate rendering.

app/render/audioparams.cpp

@@ -83,6 +83,13 @@ int AudioRenderingParams::samples_to_bytes(const int &samples) const
   return samples * channel_count() * bytes_per_sample_per_channel();
 }
 
+int AudioRenderingParams::bytes_to_samples(const int &bytes) const
+{
+  Q_ASSERT(is_valid());
+
+  return bytes / (channel_count() * bytes_per_sample_per_channel());
+}
+
 int AudioRenderingParams::channel_count() const
 {
   return av_get_channel_layout_nb_channels(channel_layout());

app/render/audioparams.h

@@ -31,6 +31,7 @@ public:
   int time_to_bytes(const rational& time) const;
   int time_to_samples(const rational& time) const;
   int samples_to_bytes(const int& samples) const;
+  int bytes_to_samples(const int &bytes) const;
   int channel_count() const;
   int bytes_per_sample_per_channel() const;
   int bits_per_sample() const;