fix stsz box, improve conditional fields handling (#119)

Author: mat-hek

lib/membrane_mp4/container.ex

@@ -18,7 +18,10 @@ defmodule Membrane.MP4.Container do
           {:box, box_name_t}
           | {:field, field_name_t}
           | {:data, bitstring}
-          | {:reason, :box_header | {:box_size, header: pos_integer, actual: pos_integer}}
+          | {:reason,
+             :box_header
+             | {:box_size, header: pos_integer, actual: pos_integer}
+             | {:non_empty_leftover, binary}}
         ]
 
   @type serialize_error_context_t :: [{:box, box_name_t} | {:field, field_name_t}]

lib/membrane_mp4/container/parse_helper.ex

@@ -26,7 +26,8 @@ defmodule Membrane.MP4.Container.ParseHelper do
           try:
             {:ok, {fields, rest}, context} <- parse_fields(content, box_schema.fields, context),
           try:
-            {:ok, children, <<>>, context} <- parse_boxes(rest, box_schema.children, context, []) do
+            {:ok, children, rest, context} <- parse_boxes(rest, box_schema.children, context, []),
+          leftover: <<>> <- rest do
       box = %{fields: fields, children: children, size: content_size, header_size: header_size}
       parse_boxes(data, schema, context, [{name, box} | acc])
     else
@@ -38,19 +39,33 @@ defmodule Membrane.MP4.Container.ParseHelper do
         box = %{content: content, size: content_size, header_size: header_size}
         parse_boxes(data, schema, context, [{name, box} | acc])
 
+      leftover: leftover ->
+        {:error, [box: name, reason: {:non_empty_leftover, leftover}]}
+
       try: {:error, context} ->
         {:error, [box: name] ++ context}
     end
   end
 
-  defp parse_fields(data, [], context) do
-    {:ok, {%{}, data}, context}
+  defp parse_fields(data, fields, context) do
+    do_parse_fields(data, fields, context, %{})
   end
 
-  defp parse_fields(data, [{name, type} | fields], context) do
-    with {:ok, {term, rest}, context} <- parse_field(data, {name, type}, context),
-         {:ok, {terms, rest}, context} <- parse_fields(rest, fields, context) do
-      {:ok, {Map.put(terms, name, term), rest}, context}
+  defp do_parse_fields(data, [], context, acc) do
+    {:ok, {acc, data}, context}
+  end
+
+  defp do_parse_fields(data, [{name, type} | fields], context, acc) do
+    case parse_field(data, {name, type}, context) do
+      {:ok, {term, rest}, context} ->
+        acc = Map.put(acc, name, term)
+        do_parse_fields(rest, fields, context, acc)
+
+      {:ok, :ignore, context} ->
+        do_parse_fields(data, fields, context, acc)
+
+      {:error, context} ->
+        {:error, context}
     end
   end
 
@@ -63,27 +78,11 @@ defmodule Membrane.MP4.Container.ParseHelper do
     end
   end
 
-  defp parse_field(data, {name, {type, store: context_name, when: {key, [mask: mask]}}}, context) do
-    context_object = Map.get(context, key, 0)
-
-    if (mask &&& context_object) == mask do
-      parse_field(data, {name, {type, store: context_name}}, context)
-    else
-      {:ok, {[], data}, context}
-    end
-  end
-
-  defp parse_field(
-         data,
-         {name, {type, store: context_name, when: {key, [value: value]}}},
-         context
-       ) do
-    context_object = Map.get(context, key, 0)
-
-    if context_object == value do
+  defp parse_field(data, {name, {type, store: context_name, when: when_clause}}, context) do
+    if handle_when(when_clause, context) do
       parse_field(data, {name, {type, store: context_name}}, context)
     else
-      {:ok, {[], data}, context}
+      {:ok, :ignore, context}
     end
   end
 
@@ -94,23 +93,11 @@ defmodule Membrane.MP4.Container.ParseHelper do
     {:ok, result, context}
   end
 
-  defp parse_field(data, {name, {type, when: {key, [mask: mask]}}}, context) do
-    context_object = Map.get(context, key, 0)
-
-    if (mask &&& context_object) == mask do
-      parse_field(data, {name, type}, context)
-    else
-      {:ok, {[], data}, context}
-    end
-  end
-
-  defp parse_field(data, {name, {type, when: {key, [value: value]}}}, context) do
-    context_object = Map.get(context, key, 0)
-
-    if context_object == value do
+  defp parse_field(data, {name, {type, when: when_clause}}, context) do
+    if handle_when(when_clause, context) do
       parse_field(data, {name, type}, context)
     else
-      {:ok, {[], data}, context}
+      {:ok, :ignore, context}
     end
   end
 
@@ -188,4 +175,16 @@ defmodule Membrane.MP4.Container.ParseHelper do
   defp parse_field_error(_data, name, context) do
     {:error, [field: name] ++ context}
   end
+
+  defp handle_when({key, condition}, context) do
+    with {:ok, value} <- Map.fetch(context, key) do
+      case condition do
+        [value: cond_value] -> value == cond_value
+        [mask: mask] -> (mask &&& value) == mask
+      end
+    else
+      :error ->
+        raise "MP4 schema field #{key} not found in context"
+    end
+  end
 end

lib/membrane_mp4/container/schema.ex

@@ -313,7 +313,7 @@ defmodule Membrane.MP4.Container.Schema do
                           fields:
                             @full_box ++
                               [
-                                sample_size: :uint32,
+                                sample_size: {:uint32, store: :sample_size},
                                 sample_count: :uint32,
                                 entry_list: {
                                   {:list,

lib/membrane_mp4/movie_box/sample_table_box.ex

@@ -12,7 +12,6 @@ defmodule Membrane.MP4.MovieBox.SampleTableBox do
     sample_deltas = assemble_sample_deltas(table)
     maybe_sample_sync = maybe_sample_sync(table)
     sample_to_chunk = assemble_sample_to_chunk(table)
-    sample_sizes = assemble_sample_sizes(table)
     chunk_offsets = assemble_chunk_offsets(table)
 
     [
@@ -47,15 +46,7 @@ defmodule Membrane.MP4.MovieBox.SampleTableBox do
                   entry_list: sample_to_chunk
                 }
               },
-              stsz: %{
-                fields: %{
-                  version: 0,
-                  flags: 0,
-                  sample_size: 0,
-                  sample_count: table.sample_count,
-                  entry_list: sample_sizes
-                }
-              },
+              stsz: assemble_stsz(table),
               stco: %{
                 fields: %{
                   version: 0,
@@ -256,12 +247,27 @@ defmodule Membrane.MP4.MovieBox.SampleTableBox do
         }
       )
 
-  defp assemble_sample_sizes(%{sample_sizes: sample_sizes}),
-    do: Enum.map(sample_sizes, &%{entry_size: &1})
-
   defp assemble_chunk_offsets(%{chunk_offsets: chunk_offsets}),
     do: Enum.map(chunk_offsets, &%{chunk_offset: &1})
 
+  defp assemble_stsz(%{sample_sizes: sample_sizes, sample_count: sample_count}) do
+    fields =
+      if sample_sizes != [] and Enum.all?(sample_sizes) == hd(sample_sizes) do
+        %{sample_size: hd(sample_sizes), entry_list: []}
+      else
+        %{sample_size: 0, entry_list: Enum.map(sample_sizes, &%{entry_size: &1})}
+      end
+
+    %{
+      fields:
+        Map.merge(fields, %{
+          version: 0,
+          flags: 0,
+          sample_count: sample_count
+        })
+    }
+  end
+
   @spec unpack(%{children: Container.t(), fields: map()}, timescale :: pos_integer()) ::
           SampleTable.t()
   def unpack(%{children: boxes}, timescale) do
@@ -293,12 +299,12 @@ defmodule Membrane.MP4.MovieBox.SampleTableBox do
     offsets |> Enum.map(fn %{chunk_offset: offset} -> offset end)
   end
 
-  defp unpack_sample_sizes(%{fields: %{entry_list: [], sample_count: 1, sample_size: sample_size}}) do
-    [sample_size]
+  defp unpack_sample_sizes(%{fields: %{sample_size: 0, entry_list: sizes}}) do
+    Enum.map(sizes, fn %{entry_size: size} -> size end)
   end
 
-  defp unpack_sample_sizes(%{fields: %{entry_list: sizes}}) do
-    sizes |> Enum.map(fn %{entry_size: size} -> size end)
+  defp unpack_sample_sizes(%{fields: %{sample_size: sample_size, sample_count: sample_count}}) do
+    Bunch.Enum.repeated(sample_size, sample_count)
   end
 
   defp unpack_sample_description(%{children: [{avc, %{children: boxes, fields: fields}}]})