decoder/renderer: no longer index automatically as part of the retrieve

functions

Indexing is a lengthy process and had a high chance of getting RenderWorkers
stuck doing it rather than being responsive to cache requests. This commit
introduces a system where workers never index media, but instead signal that
media is not ready to their RenderBackends which ensure that the media gets
indexed and re-queues the affected frames when those indexes are ready.

app/render/audioparams.cpp

@@ -83,6 +83,11 @@ int AudioRenderingParams::samples_to_bytes(const int &samples) const
   return samples * channel_count() * bytes_per_sample_per_channel();
 }
 
+rational AudioRenderingParams::samples_to_time(const int &samples) const
+{
+  return rational(samples, sample_rate());
+}
+
 int AudioRenderingParams::bytes_to_samples(const int &bytes) const
 {
   Q_ASSERT(is_valid());
@@ -90,6 +95,13 @@ int AudioRenderingParams::bytes_to_samples(const int &bytes) const
   return bytes / (channel_count() * bytes_per_sample_per_channel());
 }
 
+rational AudioRenderingParams::bytes_to_time(const int &bytes) const
+{
+  Q_ASSERT(is_valid());
+
+  return samples_to_time(bytes_to_samples(bytes));
+}
+
 int AudioRenderingParams::channel_count() const
 {
   return av_get_channel_layout_nb_channels(channel_layout());