Add multivariant output support to Membrane.Transcoder

README.md

@@ -34,6 +34,9 @@ Then you can inspect the format of the output file with e.g. `ffprobe` and confi
 ```
 ffprobe tmp/video.ivf
 ```
+
+For an example of a transcoder with multiple outputs, see `examples/multivariant_output.exs`
+
 ## Copyright and License
 
 Copyright 2020, [Software Mansion](https://swmansion.com/?utm_source=git&utm_medium=readme&utm_campaign=membrane_transcoder_plugin)

examples/multivariant_output.exs

@@ -0,0 +1,91 @@
+Mix.install([
+  :membrane_file_plugin,
+  {:membrane_transcoder_plugin, path: __DIR__ |> Path.join("..") |> Path.expand()}
+])
+
+defmodule Example do
+  alias Membrane.{H264, H265, VP8, RCPipeline}
+  require RCPipeline
+  require Membrane.Pad
+
+  import Membrane.ChildrenSpec
+
+  @doc """
+  Transcodes a single H264 input into three output files simultaneously:
+    - output 0: H264 (annexb, repackaged — no re-encode)
+    - output 1: H265 (transcoded)
+    - output 2: VP8  (transcoded)
+
+  Each output pad carries its own `output_stream_format`, `transcoding_policy`, and
+  `native_acceleration` options, all resolved independently inside the transcoder bin.
+  """
+  def run(input_file, h264_output_file, h265_output_file, vp8_output_file) do
+    pipeline = RCPipeline.start_link!()
+
+    spec = [
+      child(%Membrane.File.Source{location: input_file})
+      |> child(:parser, %H264.Parser{
+        output_stream_structure: :annexb,
+        output_alignment: :au,
+        generate_best_effort_timestamps: %{framerate: {30, 1}}
+      })
+      |> child(:transcoder, Membrane.Transcoder),
+
+      # Output 0 — keep H264, just repackage (no re-encode)
+      get_child(:transcoder)
+      |> via_out(Membrane.Pad.ref(:output, 0),
+        options: [
+          output_stream_format: %H264{alignment: :au, stream_structure: :annexb},
+          transcoding_policy: :if_needed
+        ]
+      )
+      |> child(:h264_sink, %Membrane.File.Sink{location: h264_output_file}),
+
+      # Output 1 — transcode to H265
+      get_child(:transcoder)
+      |> via_out(Membrane.Pad.ref(:output, 1),
+        options: [
+          output_stream_format: H265,
+          transcoding_policy: :always
+        ]
+      )
+      |> child(:h265_sink, %Membrane.File.Sink{location: h265_output_file}),
+
+      # Output 2 — transcode to VP8
+      get_child(:transcoder)
+      |> via_out(Membrane.Pad.ref(:output, 2),
+        options: [
+          output_stream_format: VP8,
+          transcoding_policy: :always
+        ]
+      )
+      |> child(:vp8_sink, %Membrane.File.Sink{location: vp8_output_file})
+    ]
+
+    RCPipeline.subscribe(pipeline, _any)
+    RCPipeline.exec_actions(pipeline, spec: spec)
+    RCPipeline.await_end_of_stream(pipeline, :h264_sink)
+    RCPipeline.await_end_of_stream(pipeline, :h265_sink)
+    RCPipeline.await_end_of_stream(pipeline, :vp8_sink)
+    RCPipeline.terminate(pipeline)
+  end
+end
+
+File.mkdir_p!(Path.join(__DIR__, "tmp"))
+
+input = Path.join(__DIR__, "../test/fixtures/video.h264")
+h264_out = Path.join(__DIR__, "tmp/multivariant_output.h264")
+h265_out = Path.join(__DIR__, "tmp/multivariant_output.h265")
+vp8_out = Path.join(__DIR__, "tmp/multivariant_output.ivf")
+
+IO.puts("Input:        #{input}")
+IO.puts("H264 output:  #{h264_out}")
+IO.puts("H265 output:  #{h265_out}")
+IO.puts("VP8 output:   #{vp8_out}")
+IO.puts("")
+Example.run(input, h264_out, h265_out, vp8_out)
+
+IO.puts("Done.")
+IO.puts("  #{h264_out} (#{File.stat!(h264_out).size} bytes)")
+IO.puts("  #{h265_out} (#{File.stat!(h265_out).size} bytes)")
+IO.puts("  #{vp8_out} (#{File.stat!(vp8_out).size} bytes)")

examples/vp8_to_h264.exs

@@ -20,22 +20,29 @@ Mix.install(
 defmodule Example do
   alias Membrane.{H264, RCPipeline}
   require RCPipeline
+  require Membrane.Pad
 
   import Membrane.ChildrenSpec
 
   def convert(input_file, output_file, native_acceleration) 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: H264,
-        native_acceleration: native_acceleration
-      })
-      |> child(:sink, %Membrane.File.Sink{location: output_file})
+      [
+        child(%Membrane.File.Source{
+          location: input_file
+        })
+        |> child(:deserializer, Membrane.IVF.Deserializer)
+        |> child(:transcoder, Membrane.Transcoder),
+        get_child(:transcoder)
+        |> via_out(Membrane.Pad.ref(:output, 0),
+          options: [
+            output_stream_format: H264,
+            native_acceleration: native_acceleration
+          ]
+        )
+        |> child(:sink, %Membrane.File.Sink{location: output_file})
+      ]
 
     RCPipeline.subscribe(pipeline, _any)
     RCPipeline.exec_actions(pipeline, spec: spec)