This CL begins the process of making the rendering portion of the dec…

…oder iterative.

Add structs to represent the rendering metadata that is necessary to keep track of our rendering logic. This cl also adds a new function to generate rendering metadata for submixes.

This function will be used to generate the rendering metadata for all submixes in a given mix presentation OBU. The rendering metadata will later be used to render the audio frames at each timestamp.

A subsequent cl will implement GenerateRenderingMetadataForAllLayouts().

PiperOrigin-RevId: 697736516

iamf/cli/rendering_mix_presentation_finalizer.cc

@@ -470,6 +470,95 @@ absl::Status ValidateUserLoudness(const LoudnessInfo& user_loudness,
   return absl::OkStatus();
 }
 
+// Contains rendering metadata for all audio elements in a given layout.
+struct LayoutRenderingMetadata {
+  // Controlled by the WavWriterFactory; may be nullptr if the user does not
+  // want a wav file written for this layout.
+  std::unique_ptr<WavWriter> wav_writer;
+  // Controlled by the LoudnessCalculatorFactory; may be nullptr if the user
+  // does not want loudness calculated for this layout.
+  std::unique_ptr<LoudnessCalculatorBase> loudness_calculator;
+  std::vector<AudioElementRenderingMetadata> audio_element_rendering_metadata;
+};
+
+// We need to store rendering metadata for each submix, layout, and audio
+// element. This metadata will then be used to render the audio frames at each
+// timestamp. Some metadata is common to all audio elements and all layouts
+// within a submix. We also want to optionally support writing to a wav file
+// and/or calculating loudness based on the rendered output.
+struct SubmixRenderingMetadata {
+  uint32_t common_sample_rate;
+  uint8_t common_bit_depth;
+  // This vector will contain one LayoutRenderingMetadata per layout in the
+  // submix.
+  std::vector<LayoutRenderingMetadata> layout_rendering_metadata;
+};
+
+absl::Status GenerateRenderingMetadataForLayouts(
+    uint32_t output_bit_depth,
+    std::vector<LayoutRenderingMetadata>& output_layout_rendering_metadata) {
+  return absl::UnimplementedError("Not implemented yet.");
+}
+
+// We generate one rendering metadata object for each submix. Once this
+// metadata is generated, we will loop through it to render all submixes
+// for a given timestamp. Within a submix, there can be many different audio
+// elements and layouts that need to be rendered as well. Not all of these
+// need to be rendered; only the ones that either have a wav writer or a
+// loudness calculator.
+absl::Status GenerateRenderingMetadataForSubmixes(  // NOLINT
+    const RendererFactoryBase& renderer_factory,
+    const LoudnessCalculatorFactoryBase* loudness_calculator_factory,
+    const RenderingMixPresentationFinalizer::WavWriterFactory&
+        wav_writer_factory,
+    const std::filesystem::path& file_path_prefix,
+    const absl::flat_hash_map<uint32_t, AudioElementWithData>& audio_elements,
+    const std::optional<uint32_t> output_wav_file_bit_depth_override,
+    MixPresentationObu& mix_presentation_obu,
+    std::vector<SubmixRenderingMetadata>& output_rendering_metadata) {
+  for (int sub_mix_index = 0;
+       sub_mix_index < mix_presentation_obu.sub_mixes_.size();
+       ++sub_mix_index) {
+    SubmixRenderingMetadata& submix_rendering_metadata =
+        output_rendering_metadata[sub_mix_index];
+    MixPresentationSubMix& sub_mix =
+        mix_presentation_obu.sub_mixes_[sub_mix_index];
+
+    // Pointers to audio elements in this sub mix; useful later.
+    std::vector<const AudioElementWithData*> audio_elements_in_sub_mix;
+    RETURN_IF_NOT_OK(CollectAudioElementsInSubMix(
+        audio_elements, sub_mix.audio_elements, audio_elements_in_sub_mix));
+
+    // Data common to all audio elements and layouts.
+    bool requires_resampling;
+    RETURN_IF_NOT_OK(GetCommonSampleRateAndBitDepthFromAudioElementIds(
+        audio_elements_in_sub_mix, submix_rendering_metadata.common_sample_rate,
+        submix_rendering_metadata.common_bit_depth, requires_resampling));
+    if (requires_resampling) {
+      // TODO(b/274689885): Convert to a common sample rate and/or bit-depth.
+      return absl::UnimplementedError(
+          "This implementation does not support mixing different sample rates "
+          "or bit-depths.");
+    }
+    const auto output_wav_file_bit_depth =
+        output_wav_file_bit_depth_override.has_value()
+            ? *output_wav_file_bit_depth_override
+            : submix_rendering_metadata.common_bit_depth;
+    std::vector<LayoutRenderingMetadata>& layout_rendering_metadata =
+        submix_rendering_metadata.layout_rendering_metadata;
+    RETURN_IF_NOT_OK(GenerateRenderingMetadataForLayouts(
+        output_wav_file_bit_depth, layout_rendering_metadata));
+  }
+  return absl::OkStatus();
+}
+
+// TODO(b/379727145): This function should be split up into smaller functions.
+// It is rendering and then optionally writing to a wav file and/or calculating
+// loudness based on the rendered output. We should split up the rendering part
+// from the loudness calculation part ideally and rename accordingly. It also
+// does this for each submix, each layout within a submix, and each audio
+// element at every timestamp. We want to change it such that it does similar
+// behavior for only one timestamp at a time.
 absl::Status FillLoudnessInfo(
     bool validate_loudness, const RendererFactoryBase& renderer_factory,
     const LoudnessCalculatorFactoryBase* loudness_calculator_factory,