ChannelAudioLayerConfig: Refactor existing read/write functionality…

… into `Read` and `Write` functions.

  - There is nothing being validated at the single-layer level - so these functions do not have `Validate` in the name.
  - Increase coverage here which was otherwise very light - add some tests adjacent to planned features regarding `expanded_loudspeaker_layout`.

PiperOrigin-RevId: 654013559

iamf/obu/audio_element.cc

@@ -194,23 +194,7 @@ absl::Status ValidateAndWriteScalableChannelLayout(
 
   // Loop to write the `channel_audio_layer_configs` array.
   for (const auto& layer_config : layout.channel_audio_layer_configs) {
-    RETURN_IF_NOT_OK(
-        wb.WriteUnsignedLiteral(layer_config.loudspeaker_layout, 4));
-    RETURN_IF_NOT_OK(
-        wb.WriteUnsignedLiteral(layer_config.output_gain_is_present_flag, 1));
-    RETURN_IF_NOT_OK(
-        wb.WriteUnsignedLiteral(layer_config.recon_gain_is_present_flag, 1));
-    RETURN_IF_NOT_OK(wb.WriteUnsignedLiteral(layer_config.reserved_a, 2));
-    RETURN_IF_NOT_OK(wb.WriteUnsignedLiteral(layer_config.substream_count, 8));
-    RETURN_IF_NOT_OK(
-        wb.WriteUnsignedLiteral(layer_config.coupled_substream_count, 8));
-
-    if (layer_config.output_gain_is_present_flag == 1) {
-      RETURN_IF_NOT_OK(
-          wb.WriteUnsignedLiteral(layer_config.output_gain_flag, 6));
-      RETURN_IF_NOT_OK(wb.WriteUnsignedLiteral(layer_config.reserved_b, 2));
-      RETURN_IF_NOT_OK(wb.WriteSigned16(layer_config.output_gain));
-    }
+    RETURN_IF_NOT_OK(layer_config.Write(wb));
   }
 
   return absl::OkStatus();
@@ -226,26 +210,7 @@ absl::Status ReadAndValidateScalableChannelLayout(
 
   for (int i = 0; i < layout.num_layers; ++i) {
     ChannelAudioLayerConfig layer_config;
-    uint8_t loudspeaker_layout;
-    RETURN_IF_NOT_OK(rb.ReadUnsignedLiteral(4, loudspeaker_layout));
-    layer_config.loudspeaker_layout =
-        static_cast<ChannelAudioLayerConfig::LoudspeakerLayout>(
-            loudspeaker_layout);
-    RETURN_IF_NOT_OK(
-        rb.ReadUnsignedLiteral(1, layer_config.output_gain_is_present_flag));
-    RETURN_IF_NOT_OK(
-        rb.ReadUnsignedLiteral(1, layer_config.recon_gain_is_present_flag));
-    RETURN_IF_NOT_OK(rb.ReadUnsignedLiteral(2, layer_config.reserved_a));
-    RETURN_IF_NOT_OK(rb.ReadUnsignedLiteral(8, layer_config.substream_count));
-    RETURN_IF_NOT_OK(
-        rb.ReadUnsignedLiteral(8, layer_config.coupled_substream_count));
-
-    if (layer_config.output_gain_is_present_flag == 1) {
-      RETURN_IF_NOT_OK(
-          rb.ReadUnsignedLiteral(6, layer_config.output_gain_flag));
-      RETURN_IF_NOT_OK(rb.ReadUnsignedLiteral(2, layer_config.reserved_b));
-      RETURN_IF_NOT_OK(rb.ReadSigned16(layer_config.output_gain));
-    }
+    RETURN_IF_NOT_OK(layer_config.Read(rb));
     layout.channel_audio_layer_configs.push_back(layer_config);
   }
 
@@ -414,6 +379,41 @@ absl::Status AudioElementParam::ReadAndValidate(uint32_t audio_element_id,
   }
 }
 
+absl::Status ChannelAudioLayerConfig::Write(WriteBitBuffer& wb) const {
+  RETURN_IF_NOT_OK(wb.WriteUnsignedLiteral(loudspeaker_layout, 4));
+  RETURN_IF_NOT_OK(wb.WriteUnsignedLiteral(output_gain_is_present_flag, 1));
+  RETURN_IF_NOT_OK(wb.WriteUnsignedLiteral(recon_gain_is_present_flag, 1));
+  RETURN_IF_NOT_OK(wb.WriteUnsignedLiteral(reserved_a, 2));
+  RETURN_IF_NOT_OK(wb.WriteUnsignedLiteral(substream_count, 8));
+  RETURN_IF_NOT_OK(wb.WriteUnsignedLiteral(coupled_substream_count, 8));
+
+  if (output_gain_is_present_flag == 1) {
+    RETURN_IF_NOT_OK(wb.WriteUnsignedLiteral(output_gain_flag, 6));
+    RETURN_IF_NOT_OK(wb.WriteUnsignedLiteral(reserved_b, 2));
+    RETURN_IF_NOT_OK(wb.WriteSigned16(output_gain));
+  }
+  return absl::OkStatus();
+}
+
+absl::Status ChannelAudioLayerConfig::Read(ReadBitBuffer& rb) {
+  uint8_t loudspeaker_layout_uint8;
+  RETURN_IF_NOT_OK(rb.ReadUnsignedLiteral(4, loudspeaker_layout_uint8));
+  loudspeaker_layout = static_cast<ChannelAudioLayerConfig::LoudspeakerLayout>(
+      loudspeaker_layout_uint8);
+  RETURN_IF_NOT_OK(rb.ReadUnsignedLiteral(1, output_gain_is_present_flag));
+  RETURN_IF_NOT_OK(rb.ReadUnsignedLiteral(1, recon_gain_is_present_flag));
+  RETURN_IF_NOT_OK(rb.ReadUnsignedLiteral(2, reserved_a));
+  RETURN_IF_NOT_OK(rb.ReadUnsignedLiteral(8, substream_count));
+  RETURN_IF_NOT_OK(rb.ReadUnsignedLiteral(8, coupled_substream_count));
+
+  if (output_gain_is_present_flag == 1) {
+    RETURN_IF_NOT_OK(rb.ReadUnsignedLiteral(6, output_gain_flag));
+    RETURN_IF_NOT_OK(rb.ReadUnsignedLiteral(2, reserved_b));
+    RETURN_IF_NOT_OK(rb.ReadSigned16(output_gain));
+  }
+  return absl::OkStatus();
+}
+
 absl::Status ScalableChannelLayoutConfig::Validate(
     DecodedUleb128 num_substreams_in_audio_element) const {
   if (num_layers == 0 || num_layers > 6) {

iamf/obu/audio_element.h

@@ -54,7 +54,11 @@ struct AudioElementParam {
   std::unique_ptr<ParamDefinition> param_definition;
 };
 
-/*!\brief An element of the `ScalableChannelLayoutConfig` vector. */
+/*!\brief An element of the `ScalableChannelLayoutConfig` vector.
+ *
+ * Implements the `ChannelAudioLayerConfig` as defined by section 3.6.2 of
+ * https://aomediacodec.github.io/iamf/v1.0.0-errata.html.
+ */
 struct ChannelAudioLayerConfig {
   /*!\brief A 4-bit enum for the type of layout. */
   enum LoudspeakerLayout : uint8_t {
@@ -75,6 +79,21 @@ struct ChannelAudioLayerConfig {
   friend bool operator==(const ChannelAudioLayerConfig& lhs,
                          const ChannelAudioLayerConfig& rhs) = default;
 
+  /*!\brief Writes the `ChannelAudioLayerConfig` payload to the buffer.
+   *
+   * \param wb Buffer to write to.
+   * \return `absl::OkStatus()` if the payload is valid. A specific status on
+   *     failure.
+   */
+  absl::Status Write(WriteBitBuffer& wb) const;
+
+  /*!\brief Reads the `ChannelAudioLayerConfig` payload from the buffer.
+   *
+   * \param rb Buffer to read from.
+   * \return `absl::OkStatus()` if successful. A specific status on failure.
+   */
+  absl::Status Read(ReadBitBuffer& rb);
+
   LoudspeakerLayout loudspeaker_layout;  // 4 bits.
   uint8_t output_gain_is_present_flag;   // 1 bit.
   uint8_t recon_gain_is_present_flag;    // 1 bit.

iamf/obu/tests/BUILD

@@ -37,6 +37,7 @@ cc_test(
         "//iamf/cli:leb_generator",
         "//iamf/common:read_bit_buffer",
         "//iamf/common:write_bit_buffer",
+        "//iamf/common/tests:test_utils",
         "//iamf/obu:audio_element",
         "//iamf/obu:demixing_info_param_data",
         "//iamf/obu:leb128",