renderer: switched audio rendering over to planar buffers

While planar audio cannot be used for playback, it's much easier for processing.
This should lead to cleaner and easier to write code in the future.

app/audio/sumsamples.cpp

@@ -14,6 +14,21 @@ QVector<SampleSummer::Sum> SampleSummer::SumSamples(const qfloat16 *samples, int
   return SumSamplesInternal<qfloat16>(samples, nb_samples, nb_channels);
 }
 
+QVector<SampleSummer::Sum> SampleSummer::SumSamples(SampleBufferPtr samples, int start_index, int length)
+{
+  QVector<SampleSummer::Sum> summed_samples(samples->audio_params().channel_count());
+
+  int end_index = start_index + length;
+
+  for (int i=start_index;i<end_index;i++) {
+    for (int channel=0;channel<samples->audio_params().channel_count();channel++) {
+      ClampMinMax<float>(summed_samples[channel], samples->data()[channel][i]);
+    }
+  }
+
+  return summed_samples;
+}
+
 QVector<SampleSummer::Sum> SampleSummer::ReSumSamples(const SampleSummer::Sum *samples, int nb_samples, int nb_channels)
 {
   QVector<SampleSummer::Sum> summed_samples(nb_channels);
@@ -47,18 +62,20 @@ QVector<SampleSummer::Sum> SampleSummer::SumSamplesInternal(const T *samples, in
   QVector<SampleSummer::Sum> summed_samples(nb_channels);
 
   for (int i=0;i<nb_samples;i++) {
-    int channel = i%nb_channels;
-
-    float sample = samples[i];
-
-    if (sample < summed_samples[channel].min) {
-      summed_samples[channel].min = sample;
-    }
-
-    if (sample > summed_samples[channel].max) {
-      summed_samples[channel].max = sample;
-    }
+    ClampMinMax<T>(summed_samples[i%nb_channels], samples[i]);
   }
 
   return summed_samples;
 }
+
+template<typename T>
+void SampleSummer::ClampMinMax(SampleSummer::Sum &sum, T value)
+{
+  if (value < sum.min) {
+    sum.min = value;
+  }
+
+  if (value > sum.max) {
+    sum.max = value;
+  }
+}