Initial implementation

README.md

@@ -1,31 +1,27 @@
-# Membrane Template Plugin
+# Membrane Transcider Plugin
 
 [![Hex.pm](https://img.shields.io/hexpm/v/membrane_template_plugin.svg)](https://hex.pm/packages/membrane_template_plugin)
 [![API Docs](https://img.shields.io/badge/api-docs-yellow.svg?style=flat)](https://hexdocs.pm/membrane_template_plugin)
 [![CircleCI](https://circleci.com/gh/membraneframework/membrane_template_plugin.svg?style=svg)](https://circleci.com/gh/membraneframework/membrane_template_plugin)
 
-This repository contains a template for new plugins.
-
-Check out different branches for other flavors of this template.
+This repository provides `Membrane.Transcoder` which is a bin that is capable 
+of transcoding the input audio or video stream into the descired one specified 
+with simple declarative API.
 
 It's a part of the [Membrane Framework](https://membrane.stream).
 
 ## Installation
 
-The package can be installed by adding `membrane_template_plugin` to your list of dependencies in `mix.exs`:
+The package can be installed by adding `membrane_transcoder_plugin` to your list of dependencies in `mix.exs`:
 
 ```elixir
 def deps do
   [
-    {:membrane_template_plugin, "~> 0.1.0"}
+    {:membrane_transcoder_plugin, "~> 0.1.0"}
   ]
 end
 ```
 
-## Usage
-
-TODO
-
 ## Copyright and License
 
 Copyright 2020, [Software Mansion](https://swmansion.com/?utm_source=git&utm_medium=readme&utm_campaign=membrane_template_plugin)

lib/transcoder.ex

@@ -50,7 +50,12 @@ defmodule Membrane.Transcoder do
   end
 
   @impl true
-  def handle_child_notification({:stream_format, format}, :forwarding_filter, _ctx, state) do
+  def handle_child_notification(
+        {:stream_format, format},
+        :forwarding_filter,
+        _ctx,
+        %{input_stream_format: nil} = state
+      ) do
     state =
       %{state | input_stream_format: format}
       |> resolve_output_stream_format()

lib/transcoder/audio.ex

@@ -1,18 +1,32 @@
-defmodule Boombox.Transcoder.Audio do
+defmodule Membrane.Transcoder.Audio do
   @moduledoc false
 
   import Membrane.ChildrenSpec
   require Membrane.Logger
   alias Membrane.{AAC, ChildrenSpec, Opus, RawAudio, RemoteStream}
 
   @opus_sample_rate 48_000
+  @aac_sample_rates [
+    96_000,
+    88_200,
+    64_000,
+    48_000,
+    44_100,
+    32_000,
+    24_000,
+    22_050,
+    16_000,
+    12_000,
+    11_025,
+    8000
+  ]
 
   @type audio_stream_format :: AAC.t() | Opus.t() | RawAudio.t()
 
   defguard is_audio_format(format)
            when is_struct(format) and
                   (format.__struct__ in [AAC, Opus, RawAudio] or
-                     (format.__struct__ == RemoteStream and format.content_format == Opus and
+                     (format.__struct__ == RemoteStream and format.content_format in [Opus, AAC] and
                         format.type == :packetized))
 
   @spec plug_audio_transcoding(
@@ -72,6 +86,18 @@ defmodule Boombox.Transcoder.Audio do
     })
   end
 
+  defp maybe_plug_resampler(builder, %{sample_rate: sample_rate} = input_format, %AAC{})
+       when sample_rate not in @aac_sample_rates do
+    builder
+    |> child(:resampler, %Membrane.FFmpeg.SWResample.Converter{
+      output_stream_format: %RawAudio{
+        sample_format: :s16le,
+        sample_rate: 44_100,
+        channels: input_format.channels
+      }
+    })
+  end
+
   defp maybe_plug_resampler(builder, _input_format, _output_format) do
     builder
   end

mix.exs

@@ -1,4 +1,4 @@
-defmodule Membrane.Template.Mixfile do
+defmodule Membrane.Transcoder.Plugin.Mixfile do
   use Mix.Project
 
   @version "0.1.0"
@@ -47,6 +47,8 @@ defmodule Membrane.Template.Mixfile do
       {:membrane_h265_ffmpeg_plugin, "~> 0.4.2"},
       {:membrane_ffmpeg_swresample_plugin, "~> 0.20.0"},
       {:membrane_timestamp_queue, "~> 0.2.2"},
+      {:membrane_h264_format, "~> 0.6.1"},
+      {:membrane_opus_format, "~> 0.3.0"},
       {:ex_doc, ">= 0.0.0", only: :dev, runtime: false},
       {:dialyxir, ">= 0.0.0", only: :dev, runtime: false},
       {:credo, ">= 0.0.0", only: :dev, runtime: false}