Merge pull request #2 from membraneframework/setup_ci

Setup CI. Add documentation and example of usage

Author: varsill

Diff for: .formatter.exs

@@ -1,6 +1,6 @@
 [
   inputs: [
-    "{lib,test,config}/**/*.{ex,exs}",
+    "{lib,test,config,examples}/**/*.{ex,exs}",
     ".formatter.exs",
     "*.exs"
   ],

Diff for: README.md

@@ -22,6 +22,18 @@ def deps do
 end
 ```
 
+## Usage
+In the `examples/vp8_to_h264.exs` file there is an example showing how to use 
+the `Membrane.Transcoder` to convert video encoded with VP8 into H264 encoded video.
+You can run it with the following command:
+```
+elixir vp8_to_h264.exs
+```
+
+Then you can inspect the format of the output file with e.g. `ffprobe` and confirm that it stores video encoded with H.264:
+```
+ffprobe tmp/video.ivf
+```
 ## Copyright and License
 
 Copyright 2020, [Software Mansion](https://swmansion.com/?utm_source=git&utm_medium=readme&utm_campaign=membrane_template_plugin)

Diff for: examples/vp8_to_h264.exs

@@ -0,0 +1,31 @@
+Mix.install([
+  :membrane_file_plugin,
+  :membrane_ivf_plugin,
+  {:membrane_transcoder_plugin, path: __DIR__ |> Path.join("..") |> Path.expand()}
+])
+
+defmodule Example do
+  alias Membrane.RCPipeline
+  require Membrane.RCPipeline, as: RCPipeline
+  import Membrane.ChildrenSpec
+
+  def convert(input_file, output_file) do
+    pipeline = RCPipeline.start_link!()
+
+    spec =
+      child(%Membrane.File.Source{
+        location: input_file
+      })
+      |> child(:deserializer, Membrane.IVF.Deserializer)
+      |> child(:transcoder, %Membrane.Transcoder{output_stream_format: Membrane.H264})
+      |> child(:sink, %Membrane.File.Sink{location: output_file})
+
+    RCPipeline.subscribe(pipeline, _any)
+    RCPipeline.exec_actions(pipeline, spec: spec)
+    RCPipeline.await_end_of_stream(pipeline, :sink)
+    RCPipeline.terminate(pipeline)
+  end
+end
+
+File.mkdir("tmp")
+Example.convert(Path.join("./test/fixtures", "video.ivf"), Path.join("./tmp", "video.h264"))

Diff for: lib/transcoder.ex

@@ -1,5 +1,21 @@
 defmodule Membrane.Transcoder do
-  @moduledoc false
+  @moduledoc """
+  Provides transcoding capabilities for audio and video streams in Membrane.
+
+  The bin takes an incoming stream on its input and converts it into the desired one
+  as specified by the option. Transcoding is applied only if it is neccessary.
+  The following video stream formats are supported:
+  * `Membrane.H264`
+  * `Membrane.H265`
+  * `Membrane.VP8`
+  * `Membrane.RawVideo`
+
+  The following audio stream formats are supported:
+  * `Membrane.AAC`
+  * `Membrane.Opus`
+  * `Membrane.RawAudio`
+  * `Membrane.RemoteStream{content_type: Membrane.Opus}` (only as an input stream)
+  """
   use Membrane.Bin
 
   require __MODULE__.Audio
@@ -9,6 +25,9 @@ defmodule Membrane.Transcoder do
   alias __MODULE__.{Audio, ForwardingFilter, Video}
   alias Membrane.{AAC, Funnel, H264, H265, Opus, RawAudio, RawVideo, RemoteStream, VP8}
 
+  @typedoc """
+  Describes stream formats acceptable on the bin's input and output.
+  """
   @type stream_format ::
           H264.t()
           | H265.t()
@@ -19,8 +38,14 @@ defmodule Membrane.Transcoder do
           | RemoteStream.t()
           | RawAudio.t()
 
+  @typedoc """
+  Describes stream format modules that can be used to define inputs and outputs of the bin.
+  """
   @type stream_format_module :: H264 | H265 | VP8 | RawVideo | AAC | Opus | RawAudio
 
+  @typedoc """
+  Describes a function which can be used to provide output format based on the input format.
+  """
   @type stream_format_resolver :: (stream_format() -> stream_format() | stream_format_module())
 
   def_input_pad :input,
@@ -30,7 +55,15 @@ defmodule Membrane.Transcoder do
     accepted_format: format when Audio.is_audio_format(format) or Video.is_video_format(format)
 
   def_options output_stream_format: [
-                spec: stream_format() | stream_format_module() | stream_format_resolver()
+                spec: stream_format() | stream_format_module() | stream_format_resolver(),
+                description: """
+                An option specifying desired output format.
+                Can be either:
+                * a struct being a Membrane stream format,
+                * a module in which Membrane stream format struct is defined,
+                * a function which receives input stream format as an input argument
+                and is supposed to return the desired output stream format or its module.
+                """
               ]
 
   @impl true

Diff for: lib/transcoder/video.ex

@@ -66,7 +66,6 @@ defmodule Membrane.Transcoder.Video do
   end
 
   defp maybe_plug_parser_and_decoder(builder, %VP8{}) do
-    # todo: maybe specify framerate in decoder options
     builder |> child(:vp8_decoder, %VP8.Decoder{})
   end
 
@@ -75,7 +74,6 @@ defmodule Membrane.Transcoder.Video do
   end
 
   defp maybe_plug_encoder_and_parser(builder, %H264{} = h264) do
-    # todo: specify different preset in eg. mp4
     builder
     |> child(:h264_encoder, %H264.FFmpeg.Encoder{preset: :ultrafast})
     |> child(:h264_output_parser, %H264.Parser{
@@ -85,7 +83,6 @@ defmodule Membrane.Transcoder.Video do
   end
 
   defp maybe_plug_encoder_and_parser(builder, %H265{} = h265) do
-    # todo: specify different preset in eg. mp4
     builder
     |> child(:h265_encoder, %H265.FFmpeg.Encoder{preset: :ultrafast})
     |> child(:h265_output_parser, %H265.Parser{
@@ -95,7 +92,6 @@ defmodule Membrane.Transcoder.Video do
   end
 
   defp maybe_plug_encoder_and_parser(builder, %VP8{}) do
-    # todo: check if no option is required
     builder |> child(:vp8_encoder, %VP8.Encoder{})
   end
 

Diff for: mix.lock

@@ -3,23 +3,23 @@
   "bunch": {:hex, :bunch, "1.6.1", "5393d827a64d5f846092703441ea50e65bc09f37fd8e320878f13e63d410aec7", [:mix], [], "hexpm", "286cc3add551628b30605efbe2fca4e38cc1bea89bcd0a1a7226920b3364fe4a"},
   "bunch_native": {:hex, :bunch_native, "0.5.0", "8ac1536789a597599c10b652e0b526d8833348c19e4739a0759a2bedfd924e63", [:mix], [{:bundlex, "~> 1.0", [hex: :bundlex, repo: "hexpm", optional: false]}], "hexpm", "24190c760e32b23b36edeb2dc4852515c7c5b3b8675b1a864e0715bdd1c8f80d"},
   "bundlex": {:hex, :bundlex, "1.5.3", "35d01e5bc0679510dd9a327936ffb518f63f47175c26a35e708cc29eaec0890b", [:mix], [{:bunch, "~> 1.0", [hex: :bunch, repo: "hexpm", optional: false]}, {:elixir_uuid, "~> 1.2", [hex: :elixir_uuid, repo: "hexpm", optional: false]}, {:qex, "~> 0.5", [hex: :qex, repo: "hexpm", optional: false]}, {:req, ">= 0.4.0", [hex: :req, repo: "hexpm", optional: false]}, {:zarex, "~> 1.0", [hex: :zarex, repo: "hexpm", optional: false]}], "hexpm", "debd0eac151b404f6216fc60222761dff049bf26f7d24d066c365317650cd118"},
-  "bunt": {:hex, :bunt, "0.2.1", "e2d4792f7bc0ced7583ab54922808919518d0e57ee162901a16a1b6664ef3b14", [:mix], [], "hexpm", "a330bfb4245239787b15005e66ae6845c9cd524a288f0d141c148b02603777a5"},
+  "bunt": {:hex, :bunt, "1.0.0", "081c2c665f086849e6d57900292b3a161727ab40431219529f13c4ddcf3e7a44", [:mix], [], "hexpm", "dc5f86aa08a5f6fa6b8096f0735c4e76d54ae5c9fa2c143e5a1fc7c1cd9bb6b5"},
   "coerce": {:hex, :coerce, "1.0.1", "211c27386315dc2894ac11bc1f413a0e38505d808153367bd5c6e75a4003d096", [:mix], [], "hexpm", "b44a691700f7a1a15b4b7e2ff1fa30bebd669929ac8aa43cffe9e2f8bf051cf1"},
-  "credo": {:hex, :credo, "1.7.0", "6119bee47272e85995598ee04f2ebbed3e947678dee048d10b5feca139435f75", [:mix], [{:bunt, "~> 0.2.1", [hex: :bunt, repo: "hexpm", optional: false]}, {:file_system, "~> 0.2.8", [hex: :file_system, repo: "hexpm", optional: false]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: false]}], "hexpm", "6839fcf63d1f0d1c0f450abc8564a57c43d644077ab96f2934563e68b8a769d7"},
+  "credo": {:hex, :credo, "1.7.10", "6e64fe59be8da5e30a1b96273b247b5cf1cc9e336b5fd66302a64b25749ad44d", [:mix], [{:bunt, "~> 0.2.1 or ~> 1.0", [hex: :bunt, repo: "hexpm", optional: false]}, {:file_system, "~> 0.2 or ~> 1.0", [hex: :file_system, repo: "hexpm", optional: false]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: false]}], "hexpm", "71fbc9a6b8be21d993deca85bf151df023a3097b01e09a2809d460348561d8cd"},
   "dialyxir": {:hex, :dialyxir, "1.4.1", "a22ed1e7bd3a3e3f197b68d806ef66acb61ee8f57b3ac85fc5d57354c5482a93", [:mix], [{:erlex, ">= 0.2.6", [hex: :erlex, repo: "hexpm", optional: false]}], "hexpm", "84b795d6d7796297cca5a3118444b80c7d94f7ce247d49886e7c291e1ae49801"},
-  "earmark_parser": {:hex, :earmark_parser, "1.4.35", "437773ca9384edf69830e26e9e7b2e0d22d2596c4a6b17094a3b29f01ea65bb8", [:mix], [], "hexpm", "8652ba3cb85608d0d7aa2d21b45c6fad4ddc9a1f9a1f1b30ca3a246f0acc33f6"},
+  "earmark_parser": {:hex, :earmark_parser, "1.4.41", "ab34711c9dc6212dda44fcd20ecb87ac3f3fce6f0ca2f28d4a00e4154f8cd599", [:mix], [], "hexpm", "a81a04c7e34b6617c2792e291b5a2e57ab316365c2644ddc553bb9ed863ebefa"},
   "elixir_uuid": {:hex, :elixir_uuid, "1.2.1", "dce506597acb7e6b0daeaff52ff6a9043f5919a4c3315abb4143f0b00378c097", [:mix], [], "hexpm", "f7eba2ea6c3555cea09706492716b0d87397b88946e6380898c2889d68585752"},
   "erlex": {:hex, :erlex, "0.2.6", "c7987d15e899c7a2f34f5420d2a2ea0d659682c06ac607572df55a43753aa12e", [:mix], [], "hexpm", "2ed2e25711feb44d52b17d2780eabf998452f6efda104877a3881c2f8c0c0c75"},
-  "ex_doc": {:hex, :ex_doc, "0.30.6", "5f8b54854b240a2b55c9734c4b1d0dd7bdd41f71a095d42a70445c03cf05a281", [:mix], [{:earmark_parser, "~> 1.4.31", [hex: :earmark_parser, repo: "hexpm", optional: false]}, {:makeup_elixir, "~> 0.14", [hex: :makeup_elixir, repo: "hexpm", optional: false]}, {:makeup_erlang, "~> 0.1", [hex: :makeup_erlang, repo: "hexpm", optional: false]}], "hexpm", "bd48f2ddacf4e482c727f9293d9498e0881597eae6ddc3d9562bd7923375109f"},
-  "file_system": {:hex, :file_system, "0.2.10", "fb082005a9cd1711c05b5248710f8826b02d7d1784e7c3451f9c1231d4fc162d", [:mix], [], "hexpm", "41195edbfb562a593726eda3b3e8b103a309b733ad25f3d642ba49696bf715dc"},
+  "ex_doc": {:hex, :ex_doc, "0.35.1", "de804c590d3df2d9d5b8aec77d758b00c814b356119b3d4455e4b8a8687aecaf", [:mix], [{:earmark_parser, "~> 1.4.39", [hex: :earmark_parser, repo: "hexpm", optional: false]}, {:makeup_c, ">= 0.1.0", [hex: :makeup_c, repo: "hexpm", optional: true]}, {:makeup_elixir, "~> 0.14 or ~> 1.0", [hex: :makeup_elixir, repo: "hexpm", optional: false]}, {:makeup_erlang, "~> 0.1 or ~> 1.0", [hex: :makeup_erlang, repo: "hexpm", optional: false]}, {:makeup_html, ">= 0.1.0", [hex: :makeup_html, repo: "hexpm", optional: true]}], "hexpm", "2121c6402c8d44b05622677b761371a759143b958c6c19f6558ff64d0aed40df"},
+  "file_system": {:hex, :file_system, "1.0.1", "79e8ceaddb0416f8b8cd02a0127bdbababe7bf4a23d2a395b983c1f8b3f73edd", [:mix], [], "hexpm", "4414d1f38863ddf9120720cd976fce5bdde8e91d8283353f0e31850fa89feb9e"},
   "finch": {:hex, :finch, "0.19.0", "c644641491ea854fc5c1bbaef36bfc764e3f08e7185e1f084e35e0672241b76d", [:mix], [{:mime, "~> 1.0 or ~> 2.0", [hex: :mime, repo: "hexpm", optional: false]}, {:mint, "~> 1.6.2 or ~> 1.7", [hex: :mint, repo: "hexpm", optional: false]}, {:nimble_options, "~> 0.4 or ~> 1.0", [hex: :nimble_options, repo: "hexpm", optional: false]}, {:nimble_pool, "~> 1.1", [hex: :nimble_pool, repo: "hexpm", optional: false]}, {:telemetry, "~> 0.4 or ~> 1.0", [hex: :telemetry, repo: "hexpm", optional: false]}], "hexpm", "fc5324ce209125d1e2fa0fcd2634601c52a787aff1cd33ee833664a5af4ea2b6"},
   "heap": {:hex, :heap, "2.0.2", "d98cb178286cfeb5edbcf17785e2d20af73ca57b5a2cf4af584118afbcf917eb", [:mix], [], "hexpm", "ba9ea2fe99eb4bcbd9a8a28eaf71cbcac449ca1d8e71731596aace9028c9d429"},
   "hpax": {:hex, :hpax, "1.0.0", "28dcf54509fe2152a3d040e4e3df5b265dcb6cb532029ecbacf4ce52caea3fd2", [:mix], [], "hexpm", "7f1314731d711e2ca5fdc7fd361296593fc2542570b3105595bb0bc6d0fad601"},
-  "jason": {:hex, :jason, "1.4.1", "af1504e35f629ddcdd6addb3513c3853991f694921b1b9368b0bd32beb9f1b63", [:mix], [{:decimal, "~> 1.0 or ~> 2.0", [hex: :decimal, repo: "hexpm", optional: true]}], "hexpm", "fbb01ecdfd565b56261302f7e1fcc27c4fb8f32d56eab74db621fc154604a7a1"},
+  "jason": {:hex, :jason, "1.4.4", "b9226785a9aa77b6857ca22832cffa5d5011a667207eb2a0ad56adb5db443b8a", [:mix], [{:decimal, "~> 1.0 or ~> 2.0", [hex: :decimal, repo: "hexpm", optional: true]}], "hexpm", "c5eb0cab91f094599f94d55bc63409236a8ec69a21a67814529e8d5f6cc90b3b"},
   "logger_backends": {:hex, :logger_backends, "1.0.0", "09c4fad6202e08cb0fbd37f328282f16539aca380f512523ce9472b28edc6bdf", [:mix], [], "hexpm", "1faceb3e7ec3ef66a8f5746c5afd020e63996df6fd4eb8cdb789e5665ae6c9ce"},
-  "makeup": {:hex, :makeup, "1.1.0", "6b67c8bc2882a6b6a445859952a602afc1a41c2e08379ca057c0f525366fc3ca", [:mix], [{:nimble_parsec, "~> 1.2.2 or ~> 1.3", [hex: :nimble_parsec, repo: "hexpm", optional: false]}], "hexpm", "0a45ed501f4a8897f580eabf99a2e5234ea3e75a4373c8a52824f6e873be57a6"},
-  "makeup_elixir": {:hex, :makeup_elixir, "0.16.1", "cc9e3ca312f1cfeccc572b37a09980287e243648108384b97ff2b76e505c3555", [:mix], [{:makeup, "~> 1.0", [hex: :makeup, repo: "hexpm", optional: false]}, {:nimble_parsec, "~> 1.2.3 or ~> 1.3", [hex: :nimble_parsec, repo: "hexpm", optional: false]}], "hexpm", "e127a341ad1b209bd80f7bd1620a15693a9908ed780c3b763bccf7d200c767c6"},
-  "makeup_erlang": {:hex, :makeup_erlang, "0.1.2", "ad87296a092a46e03b7e9b0be7631ddcf64c790fa68a9ef5323b6cbb36affc72", [:mix], [{:makeup, "~> 1.0", [hex: :makeup, repo: "hexpm", optional: false]}], "hexpm", "f3f5a1ca93ce6e092d92b6d9c049bcda58a3b617a8d888f8e7231c85630e8108"},
+  "makeup": {:hex, :makeup, "1.2.1", "e90ac1c65589ef354378def3ba19d401e739ee7ee06fb47f94c687016e3713d1", [:mix], [{:nimble_parsec, "~> 1.4", [hex: :nimble_parsec, repo: "hexpm", optional: false]}], "hexpm", "d36484867b0bae0fea568d10131197a4c2e47056a6fbe84922bf6ba71c8d17ce"},
+  "makeup_elixir": {:hex, :makeup_elixir, "1.0.1", "e928a4f984e795e41e3abd27bfc09f51db16ab8ba1aebdba2b3a575437efafc2", [:mix], [{:makeup, "~> 1.0", [hex: :makeup, repo: "hexpm", optional: false]}, {:nimble_parsec, "~> 1.2.3 or ~> 1.3", [hex: :nimble_parsec, repo: "hexpm", optional: false]}], "hexpm", "7284900d412a3e5cfd97fdaed4f5ed389b8f2b4cb49efc0eb3bd10e2febf9507"},
+  "makeup_erlang": {:hex, :makeup_erlang, "1.0.1", "c7f58c120b2b5aa5fd80d540a89fdf866ed42f1f3994e4fe189abebeab610839", [:mix], [{:makeup, "~> 1.0", [hex: :makeup, repo: "hexpm", optional: false]}], "hexpm", "8a89a1eeccc2d798d6ea15496a6e4870b75e014d1af514b1b71fa33134f57814"},
   "membrane_aac_fdk_plugin": {:hex, :membrane_aac_fdk_plugin, "0.18.9", "1bf4ee0e5fc5bae3eae1b8f2d100d71e41f2bfaaa366ac3c6267572f6bd71f24", [:mix], [{:bunch, "~> 1.4", [hex: :bunch, repo: "hexpm", optional: false]}, {:bundlex, "~> 1.3", [hex: :bundlex, repo: "hexpm", optional: false]}, {:membrane_aac_format, "~> 0.8.0", [hex: :membrane_aac_format, repo: "hexpm", optional: false]}, {:membrane_common_c, "~> 0.16.0", [hex: :membrane_common_c, repo: "hexpm", optional: false]}, {:membrane_core, "~> 1.0", [hex: :membrane_core, repo: "hexpm", optional: false]}, {:membrane_precompiled_dependency_provider, "~> 0.1.0", [hex: :membrane_precompiled_dependency_provider, repo: "hexpm", optional: false]}, {:membrane_raw_audio_format, "~> 0.12.0", [hex: :membrane_raw_audio_format, repo: "hexpm", optional: false]}, {:unifex, "~> 1.1", [hex: :unifex, repo: "hexpm", optional: false]}], "hexpm", "aed8f58eac2c465d1e2731179f81969cb212990163c6fdf1aa27679658969be0"},
   "membrane_aac_format": {:hex, :membrane_aac_format, "0.8.0", "515631eabd6e584e0e9af2cea80471fee6246484dbbefc4726c1d93ece8e0838", [:mix], [{:bimap, "~> 1.1", [hex: :bimap, repo: "hexpm", optional: false]}], "hexpm", "a30176a94491033ed32be45e51d509fc70a5ee6e751f12fd6c0d60bd637013f6"},
   "membrane_aac_plugin": {:hex, :membrane_aac_plugin, "0.19.0", "58a15efaaa4f2cc91b968464cfd269244e035efdd983aac2e3ddeb176fcf0585", [:mix], [{:bunch, "~> 1.0", [hex: :bunch, repo: "hexpm", optional: false]}, {:membrane_aac_format, "~> 0.8.0", [hex: :membrane_aac_format, repo: "hexpm", optional: false]}, {:membrane_core, "~> 1.0", [hex: :membrane_core, repo: "hexpm", optional: false]}], "hexpm", "eb7e786e650608ee205f4eebff4c1df3677e545acf09802458f77f64f9942fe9"},
@@ -48,7 +48,7 @@
   "mint": {:hex, :mint, "1.6.2", "af6d97a4051eee4f05b5500671d47c3a67dac7386045d87a904126fd4bbcea2e", [:mix], [{:castore, "~> 0.1.0 or ~> 1.0", [hex: :castore, repo: "hexpm", optional: true]}, {:hpax, "~> 0.1.1 or ~> 0.2.0 or ~> 1.0", [hex: :hpax, repo: "hexpm", optional: false]}], "hexpm", "5ee441dffc1892f1ae59127f74afe8fd82fda6587794278d924e4d90ea3d63f9"},
   "mockery": {:hex, :mockery, "2.3.3", "3dba87bd0422a513e6af6e0d811383f38f82ac6be5d3d285a5fcca9c299bd0ac", [:mix], [], "hexpm", "17282be00613286254298117cd25e607a39f15ac03b41c631f60e52f5b5ec974"},
   "nimble_options": {:hex, :nimble_options, "1.1.1", "e3a492d54d85fc3fd7c5baf411d9d2852922f66e69476317787a7b2bb000a61b", [:mix], [], "hexpm", "821b2470ca9442c4b6984882fe9bb0389371b8ddec4d45a9504f00a66f650b44"},
-  "nimble_parsec": {:hex, :nimble_parsec, "1.3.1", "2c54013ecf170e249e9291ed0a62e5832f70a476c61da16f6aac6dca0189f2af", [:mix], [], "hexpm", "2682e3c0b2eb58d90c6375fc0cc30bc7be06f365bf72608804fb9cffa5e1b167"},
+  "nimble_parsec": {:hex, :nimble_parsec, "1.4.0", "51f9b613ea62cfa97b25ccc2c1b4216e81df970acd8e16e8d1bdc58fef21370d", [:mix], [], "hexpm", "9c565862810fb383e9838c1dd2d7d2c437b3d13b267414ba6af33e50d2d1cf28"},
   "nimble_pool": {:hex, :nimble_pool, "1.1.0", "bf9c29fbdcba3564a8b800d1eeb5a3c58f36e1e11d7b7fb2e084a643f645f06b", [:mix], [], "hexpm", "af2e4e6b34197db81f7aad230c1118eac993acc0dae6bc83bac0126d4ae0813a"},
   "numbers": {:hex, :numbers, "5.2.4", "f123d5bb7f6acc366f8f445e10a32bd403c8469bdbce8ce049e1f0972b607080", [:mix], [{:coerce, "~> 1.0", [hex: :coerce, repo: "hexpm", optional: false]}, {:decimal, "~> 1.9 or ~> 2.0", [hex: :decimal, repo: "hexpm", optional: true]}], "hexpm", "eeccf5c61d5f4922198395bf87a465b6f980b8b862dd22d28198c5e6fab38582"},
   "qex": {:hex, :qex, "0.5.1", "0d82c0f008551d24fffb99d97f8299afcb8ea9cf99582b770bd004ed5af63fd6", [:mix], [], "hexpm", "935a39fdaf2445834b95951456559e9dc2063d0a055742c558a99987b38d6bab"},

Diff for: test/integration_test.exs

@@ -3,7 +3,7 @@ defmodule Membrane.Transcoder.IntegrationTest do
   import Membrane.Testing.Assertions
   import Membrane.ChildrenSpec
 
-  alias Membrane.{H264, H265, VP8, RawVideo, AAC, Opus, RawAudio}
+  alias Membrane.{AAC, H264, H265, Opus, RawAudio, RawVideo, VP8}
   alias Membrane.Testing.Pipeline
   alias Membrane.Transcoder.Support.Preprocessors
 

Diff for: test/support/preprocessors.ex

@@ -1,4 +1,5 @@
 defmodule Membrane.Transcoder.Support.Preprocessors do
+  @moduledoc false
   import Membrane.ChildrenSpec
 
   @raw_audio_stream_format %Membrane.RawAudio{
@@ -7,6 +8,7 @@ defmodule Membrane.Transcoder.Support.Preprocessors do
     sample_format: :s16le
   }
 
+  @spec decode_h264(Membrane.ChildrenSpec.builder()) :: Membrane.ChildrenSpec.builder()
   def decode_h264(link_builder) do
     child(link_builder, %Membrane.H264.Parser{
       output_alignment: :au,
@@ -16,6 +18,7 @@ defmodule Membrane.Transcoder.Support.Preprocessors do
     |> child(%Membrane.H264.FFmpeg.Decoder{})
   end
 
+  @spec parse_h264(Membrane.ChildrenSpec.builder()) :: Membrane.ChildrenSpec.builder()
   def parse_h264(link_builder) do
     child(link_builder, %Membrane.H264.Parser{
       output_alignment: :au,
@@ -24,6 +27,7 @@ defmodule Membrane.Transcoder.Support.Preprocessors do
     })
   end
 
+  @spec parse_h265(Membrane.ChildrenSpec.builder()) :: Membrane.ChildrenSpec.builder()
   def parse_h265(link_builder) do
     child(link_builder, %Membrane.H265.Parser{
       output_alignment: :au,
@@ -32,21 +36,25 @@ defmodule Membrane.Transcoder.Support.Preprocessors do
     })
   end
 
+  @spec parse_vp8(Membrane.ChildrenSpec.builder()) :: Membrane.ChildrenSpec.builder()
   def parse_vp8(link_builder) do
     child(link_builder, Membrane.IVF.Deserializer)
   end
 
+  @spec parse_raw_audio(Membrane.ChildrenSpec.builder()) :: Membrane.ChildrenSpec.builder()
   def parse_raw_audio(link_builder) do
     child(link_builder, %Membrane.RawAudioParser{
       stream_format: @raw_audio_stream_format,
       overwrite_pts?: true
     })
   end
 
+  @spec parse_aac(Membrane.ChildrenSpec.builder()) :: Membrane.ChildrenSpec.builder()
   def parse_aac(link_builder) do
     child(link_builder, %Membrane.AAC.Parser{out_encapsulation: :ADTS})
   end
 
+  @spec parse_opus(Membrane.ChildrenSpec.builder()) :: Membrane.ChildrenSpec.builder()
   def parse_opus(link_builder) do
     child(link_builder, %Membrane.Opus.Parser{
       input_delimitted?: true,