address CR

lib/membrane_mp4/muxer/isom.ex

@@ -96,27 +96,36 @@ defmodule Membrane.MP4.Muxer.ISOM do
   @impl true
   def handle_stream_format(
         Pad.ref(:input, pad_ref) = pad,
-        %type{} = stream_format,
+        stream_format,
         ctx,
         state
       ) do
-    case ctx.pads[pad].stream_format do
+    case {ctx.pads[pad].stream_format, stream_format} do
       # Handle receiving the first stream format on the given pad
-      nil ->
+      {nil, new_format} ->
         update_in(state, [:pad_to_track, pad_ref], fn track_id ->
-          Track.new(track_id, stream_format, state.chunk_duration)
+          Track.new(track_id, new_format, state.chunk_duration)
         end)
 
-      # Handle receiving a stream format of the same type
-      %^type{} ->
+      # If the stream format is identical or remains H264 AVC3 or H265,
+      # we can be reasonably sure that the stream can still be appended
+      # to the same MP4
+      {stream_format, stream_format} ->
         state
 
-      # otherwise we can assume that output will be corrupted
-      previos_format ->
+      {%Membrane.H264{stream_structure: {:avc3, _dcr1}},
+       %Membrane.H264{stream_structure: {:avc3, _dcr2}}} ->
+        state
+
+      {%Membrane.H265{}, %Membrane.H265{}} ->
+        state
+
+      # Otherwise we can assume that output will be corrupted
+      {prev_format, new_format} ->
         raise """
         Unsupported stream_format change on pad #{inspect(pad_ref)}, \
-        previous format: #{inspect(previos_format)}
-        new format: #{inspect(stream_format)}
+        previous format: #{inspect(prev_format)}
+        new format: #{inspect(new_format)}
         """
     end
     |> then(&{[], &1})

test/membrane_mp4/muxer/isom/integration_test.exs

@@ -228,4 +228,31 @@ defmodule Membrane.MP4.Muxer.ISOM.IntegrationTest do
       perform_test(pid, "two_tracks_fast_start")
     end
   end
+
+  describe "ctts table" do
+    test "should not be stored when dts and pts values are equal" do
+      prepare_test("video")
+
+      structure = [
+        child(:file, %Membrane.File.Source{location: "test/fixtures/in_video.h264"})
+        |> child(:parser, %Membrane.H264.Parser{
+          generate_best_effort_timestamps: %{framerate: {30, 1}, add_dts_offset: false},
+          output_stream_structure: :avc1
+        })
+        |> child(:muxer, %Membrane.MP4.Muxer.ISOM{chunk_duration: Time.seconds(1)})
+        |> child(:sink, %Membrane.File.Sink{location: out_path_for("video")})
+      ]
+
+      pid = Pipeline.start_link_supervised!(spec: structure)
+
+      assert_end_of_stream(pid, :sink, :input)
+      refute_sink_buffer(pid, :sink, _buffer, 0)
+
+      assert :ok == Pipeline.terminate(pid)
+
+      assert {parsed_out, <<>>} = out_path_for("video") |> File.read!() |> Container.parse!()
+      assert Container.get_box(parsed_out, [:moov, :trak, :mdia, :minf, :stbl, :stts])
+      refute Container.get_box(parsed_out, [:moov, :trak, :mdia, :minf, :stbl, :ctts])
+    end
+  end
 end