Revoke the unecessary change. Set channels as nil in AAC struct if they are AOT_specific

Author: varsill

lib/membrane/aac/parser/audio_specific_config.ex

@@ -23,7 +23,7 @@ defmodule Membrane.AAC.Parser.AudioSpecificConfig do
       depends_on_core_coder::1, extension_flag::1>>
   end
 
-  @spec parse_audio_specific_config(binary()) :: map()
+  @spec parse_audio_specific_config(binary()) :: AAC.t()
   def parse_audio_specific_config(audio_specific_config) do
     <<profile::5, frequency_id::4, audio_specific_config_rest::bitstring>> = audio_specific_config
 
@@ -37,11 +37,15 @@ defmodule Membrane.AAC.Parser.AudioSpecificConfig do
         do: custom_frequency,
         else: AAC.sampling_frequency_id_to_sample_rate(frequency_id)
 
-    %{
+    %AAC{
       profile: AAC.aot_id_to_profile(profile),
       mpeg_version: 4,
       sample_rate: sample_rate,
-      channels: AAC.channel_config_id_to_channels(channel_config_id),
+      channels:
+        case AAC.channel_config_id_to_channels(channel_config_id) do
+          :AOT_specific -> nil
+          channels -> channels
+        end,
       encapsulation: :none,
       samples_per_frame: AAC.frame_length_id_to_samples_per_frame(frame_length_id),
       config: {:audio_specific_config, audio_specific_config}

lib/membrane/aac/parser/config.ex

@@ -39,23 +39,17 @@ defmodule Membrane.AAC.Parser.Config do
           """)
         end)
 
-        esds_stream_format =
-          if esds_stream_format.channels == :AOT_specific do
-            # It means that the set of channels is described
-            # in the channel configutation, as specified by
-            # MPEG-4 p. 3, section 4.4.1.1.
-            # In our case it's sufficient
-            # to just read the number of channels
-            %{esds_stream_format | channels: stream_format.channels}
-          else
-            esds_stream_format
-          end
-
-        struct(AAC, esds_stream_format)
+        if is_nil(esds_stream_format.channels) do
+          # channels == nil means the channel config ID was 0 (AOT_specific),
+          # meaning the channel layout is described in the bitstream per
+          # MPEG-4 p. 3, section 4.4.1.1. Fall back to the outer stream_format.
+          %{esds_stream_format | channels: stream_format.channels}
+        else
+          esds_stream_format
+        end
 
       {:audio_specific_config, audio_specific_config} ->
-        format = AudioSpecificConfig.parse_audio_specific_config(audio_specific_config)
-        struct(AAC, format)
+        AudioSpecificConfig.parse_audio_specific_config(audio_specific_config)
 
       nil ->
         stream_format

lib/membrane/aac/parser/esds.ex

@@ -40,7 +40,7 @@ defmodule Membrane.AAC.Parser.Esds do
     <<section_no, type_tag::binary, byte_size(payload), payload::binary>>
   end
 
-  @spec parse_esds(binary()) :: map()
+  @spec parse_esds(binary()) :: AAC.t()
   def parse_esds(esds) do
     {section_3, <<>>} = unpack_esds_section(esds, 3)