store ctts table on muxing

membraneframework · Jul 8, 2024 · a773a85 · a773a85
1 parent 72d38a0
commit a773a85
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Showing 9 changed files with 52 additions and 5 deletions.
diff --git a/lib/membrane_mp4/demuxer/isom/samples_info.ex b/lib/membrane_mp4/demuxer/isom/samples_info.ex
@@ -106,7 +106,7 @@ defmodule Membrane.MP4.Demuxer.ISOM.SamplesInfo do
     {dts, pts} =
       case samples_info.last_dts[track_id] do
         nil ->
-          {0, 0}
+          {0, scalify(sample_composition_offset, timescale)}
 
         last_dts ->
           {last_dts + scalify(delta, timescale),

diff --git a/lib/membrane_mp4/movie_box/sample_table_box.ex b/lib/membrane_mp4/movie_box/sample_table_box.ex
@@ -35,6 +35,7 @@ defmodule Membrane.MP4.MovieBox.SampleTableBox do
               }
             }
           ] ++
+            maybe_sample_composition_offsets(table) ++
             maybe_sample_sync ++
             [
               stsc: %{
@@ -197,6 +198,33 @@ defmodule Membrane.MP4.MovieBox.SampleTableBox do
         %{sample_count: count, sample_delta: Helper.timescalify(delta, timescale)}
       end)
 
+  defp maybe_sample_composition_offsets(%{composition_offsets: []}), do: []
+
+  defp maybe_sample_composition_offsets(%{composition_offsets: [%{sample_composition_offset: 0}]}),
+    do: []
+
+  defp maybe_sample_composition_offsets(%{
+         timescale: timescale,
+         composition_offsets: composition_offsets
+       }) do
+    composition_offsets
+    |> Enum.map(fn %{sample_count: count, sample_composition_offset: offset} ->
+      %{sample_count: count, sample_composition_offset: Helper.timescalify(offset, timescale)}
+    end)
+    |> then(
+      &[
+        ctts: %{
+          fields: %{
+            version: 0,
+            flags: 0,
+            entry_count: length(&1),
+            entry_list: &1
+          }
+        }
+      ]
+    )
+  end
+
   defp maybe_sample_sync(%{sync_samples: []}), do: []
 
   defp maybe_sample_sync(%{sync_samples: sync_samples}) do

diff --git a/lib/membrane_mp4/track/sample_table.ex b/lib/membrane_mp4/track/sample_table.ex
@@ -63,6 +63,7 @@ defmodule Membrane.MP4.Track.SampleTable do
     |> maybe_store_first_dts(buffer)
     |> do_store_sample(buffer)
     |> update_decoding_deltas(buffer)
+    |> update_composition_offsets(buffer)
     |> maybe_store_sync_sample(buffer)
     |> store_last_dts(buffer)
   end
@@ -100,6 +101,7 @@ defmodule Membrane.MP4.Track.SampleTable do
       :sync_samples,
       :chunk_offsets,
       :decoding_deltas,
+      :composition_offsets,
       :samples_per_chunk
     ]
 
@@ -148,6 +150,23 @@ defmodule Membrane.MP4.Track.SampleTable do
     end)
   end
 
+  defp update_composition_offsets(sample_table, %Buffer{dts: dts, pts: pts}) do
+    Map.update!(sample_table, :composition_offsets, fn previous_offsets ->
+      new_offset = pts - dts
+
+      case previous_offsets do
+        [] ->
+          [%{sample_count: 1, sample_composition_offset: new_offset}]
+
+        [%{sample_count: count, sample_composition_offset: ^new_offset} | rest] ->
+          [%{sample_count: count + 1, sample_composition_offset: new_offset} | rest]
+
+        _different_delta_or_empty ->
+          [%{sample_count: 1, sample_composition_offset: new_offset} | previous_offsets]
+      end
+    end)
+  end
+
   defp maybe_store_sync_sample(sample_table, %Buffer{metadata: %{h264: h264}})
        when h264.key_frame? do
     Map.update!(sample_table, :sync_samples, &[sample_table.sample_count | &1])

diff --git a/test/fixtures/isom/ref_two_tracks.mp4 b/test/fixtures/isom/ref_two_tracks.mp4
diff --git a/test/fixtures/isom/ref_two_tracks_fast_start.mp4 b/test/fixtures/isom/ref_two_tracks_fast_start.mp4
diff --git a/test/fixtures/isom/ref_video.mp4 b/test/fixtures/isom/ref_video.mp4
diff --git a/test/fixtures/isom/ref_video_fast_start.mp4 b/test/fixtures/isom/ref_video_fast_start.mp4
diff --git a/test/fixtures/isom/ref_video_hevc.mp4 b/test/fixtures/isom/ref_video_hevc.mp4
diff --git a/test/membrane_mp4/muxer/isom/integration_test.exs b/test/membrane_mp4/muxer/isom/integration_test.exs
@@ -50,7 +50,7 @@ defmodule Membrane.MP4.Muxer.ISOM.IntegrationTest do
       structure = [
         child(:file, %Membrane.File.Source{location: "test/fixtures/in_video.h264"})
         |> child(:parser, %Membrane.H264.Parser{
-          generate_best_effort_timestamps: %{framerate: {30, 1}},
+          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)})
@@ -119,7 +119,7 @@ defmodule Membrane.MP4.Muxer.ISOM.IntegrationTest do
           chunk_size: 2_000_048
         })
         |> child(:video_parser, %Membrane.H264.Parser{
-          generate_best_effort_timestamps: %{framerate: {30, 1}},
+          generate_best_effort_timestamps: %{framerate: {30, 1}, add_dts_offset: false},
           output_stream_structure: :avc1
         }),
         child(:audio_file, %Membrane.File.Source{
@@ -149,7 +149,7 @@ defmodule Membrane.MP4.Muxer.ISOM.IntegrationTest do
       structure = [
         child(:file, %Membrane.File.Source{location: "test/fixtures/in_video.h264"})
         |> child(:parser, %Membrane.H264.Parser{
-          generate_best_effort_timestamps: %{framerate: {30, 1}},
+          generate_best_effort_timestamps: %{framerate: {30, 1}, add_dts_offset: false},
           output_stream_structure: :avc1
         })
         |> child(:muxer, %Membrane.MP4.Muxer.ISOM{
@@ -188,7 +188,7 @@ defmodule Membrane.MP4.Muxer.ISOM.IntegrationTest do
       structure = [
         child(:video_file, %Membrane.File.Source{location: "test/fixtures/in_video.h264"})
         |> child(:video_parser, %Membrane.H264.Parser{
-          generate_best_effort_timestamps: %{framerate: {30, 1}},
+          generate_best_effort_timestamps: %{framerate: {30, 1}, add_dts_offset: false},
           output_stream_structure: :avc1
         }),
         child(:audio_file, %Membrane.File.Source{location: "test/fixtures/in_audio.aac"})