Motown: Change media type (stream type) representation

mojo/services/media/common/interfaces/media_types.mojom

Index: mojo/services/media/common/interfaces/media_types.mojom
diff --git a/mojo/services/media/common/interfaces/media_types.mojom b/mojo/services/media/common/interfaces/media_types.mojom
index 0babb662a91b70aa6b242a355603bcc693e487f7..3a86b32ffbc9fecd8cb1ed7ff1c9d38ffcca8689 100644
--- a/mojo/services/media/common/interfaces/media_types.mojom
+++ b/mojo/services/media/common/interfaces/media_types.mojom
@@ -5,118 +5,80 @@
 [DartPackage="mojo_services"]
 module mojo.media;
 
-// Specifies the type of media.
+// Describes the type of media.
 struct MediaType {
-  // Broadly identifies the media type and indicates how the details field is
-  // to be interpreted.
-  MediaTypeScheme scheme;
+  const string kAudioEncodingLpcm = "lpcm";

[kulakowski, 2016/04/19 19:18:22]

I feel like I don't know enough about mature media frameworks to know if a
representation of medium and encoding in a string like this will lead you to the
place you want when there are many, many more types. Might be a place for Jeff
to weigh in.

[dalesat, 2016/04/19 19:47:03]

Medium isn't encoded as a string. There are four of them, and we'll have to
revise the mojom if we want more.

We want to be able to add encodings when new compression formats are invented,
hence the string. Currently, there's no convention for managing the namespace.
We could consider using a url.

[kulakowski, 2016/04/20 17:42:37]

Sure.

I suppose I was considering Audio and Video to be types of media, which do occur
in the identifiers, not the string values.

+  const string kAudioEncodingVorbis = "vorbis";
+  const string kVideoEncodingUncompressed = "uncompressed_video";
+  const string kVideoEncodingTheora = "theora";
 
-  // Scheme-dependent details.
-  MediaTypeDetails? details;
-};
-
-// Specifies a set of types of media.
-// TODO(dalesat): Consider eliminating type sets.
-struct MediaTypeSet {
-  // Broadly identifies the media types and indicates how the details field is
-  // to be interpreted.
-  MediaTypeScheme scheme;
-
-  // Scheme-dependent details.
-  MediaTypeSetDetails? details;
-};
-
-// Media type schemes. A media type scheme broadly identifies a media type and
-// indicates what structure, if any, is used to specify the details of the type.
-// If a scheme XYZ has details, then there should be structure definitions for
-// XyzMediaTypeDetails and XyzMediaTypeSetDetails, and fields of those types
-// should appear in MediaTypeDetails and MediaTypeSetDetails respectively.
-// TODO(dalesat): Placeholder schemes could go away as part of eliminating
-// or simplifying type sets.
-enum MediaTypeScheme {
-  // Placeholder indicating type is unknown.
-  UNKNOWN,
-
-  // Placeholder indicating no type.
-  NONE,
+  // Identifies the type’s medium.
+  MediaTypeMedium medium;
 
-  // Placeholder indicating any elementary type.
-  ANY_ELEMENTARY,
+  // Medium-dependent details.
+  MediaTypeDetails details;
 
-  // Placeholder indicating any audio type.
-  ANY_AUDIO,
+  // Encoding.
+  string encoding;
 
-  // Placeholder indicating any video type.
-  ANY_VIDEO,
-
-  // Placeholder indicating any subpicture type.
-  ANY_SUBPICTURE,
-
-  // Placeholder indicating any text type.
-  ANY_TEXT,
-
-  // Placeholder indicating any multiplexed type.
-  ANY_MULTIPLEXED,
-
-  // Placeholder indicating any type.
-  ANY,
+  // Encoding-specific parameters.
+  array<uint8>? encoding_parameters;
+};
 
-  // Indicates a multiplexed type. See MultiplexedMediaTypeDetails and
-  // MultiplexedMediaTypeSetDetails.
-  MULTIPLEXED,
+// Describes a set of types of media.
+struct MediaTypeSet {
+  // Identifies the types’ medium.
+  MediaTypeMedium medium;
 
-  // Indicates LPCM audio. See LpcmMediaTypeDetails and LpcmMediaTypeSetDetails.
-  LPCM,
+  // Medium-dependent details.
+  MediaTypeSetDetails details;
 
-  // Indicates compressed audio. See CompressedAudioMediaTypeDetails and
-  // CompressedAudioMediaTypeSetDetails.
-  COMPRESSED_AUDIO,
+  // Included encodings.
+  array<string> encodings;
+};
 
-  // Indicates video. See VideoMediaTypeDetails and VideoMediaTypeSetDetails.
-  // TODO(dalesat): One scheme for video won't be adequate.
+// Medium values for MediaType
+enum MediaTypeMedium {
+  AUDIO,
   VIDEO,
+  TEXT,
+  SUBPICTURE
 };
 
 // A union of all media type details.
 union MediaTypeDetails {
-  // Each field name should correspond to a value in MediaTypeScheme.
-  MultiplexedMediaTypeDetails multiplexed;
-  LpcmMediaTypeDetails lpcm;
-  CompressedAudioMediaTypeDetails compressed_audio;
+  AudioMediaTypeDetails audio;
   VideoMediaTypeDetails video;
+  TextMediaTypeDetails text;
+  SubpictureMediaTypeDetails subpicture;
 };
 
 // A union of all media type set details.
 union MediaTypeSetDetails {
-  // Each field name should correspond to a value in MediaTypeScheme.
-  MultiplexedMediaTypeSetDetails multiplexed;
-  LpcmMediaTypeSetDetails lpcm;
-  CompressedAudioMediaTypeSetDetails compressed_audio;
+  AudioMediaTypeSetDetails audio;
   VideoMediaTypeSetDetails video;
+  TextMediaTypeSetDetails text;
+  SubpictureMediaTypeSetDetails subpicture;
 };
 
-// MediaType details for the LPCM scheme.
-struct LpcmMediaTypeDetails {
-  LpcmSampleFormat sample_format;
+// Media type details for the AUDIO medium.
+struct AudioMediaTypeDetails {
+  AudioSampleFormat sample_format;
   uint32 channels;
   uint32 frames_per_second;
   // TODO(dalesat): Channel designations.
 };
 
-// MediaTypeSet details for the LPCM scheme.
-struct LpcmMediaTypeSetDetails {
-  LpcmSampleFormat sample_format;
+// Media type set details for the AUDIO medium.
+struct AudioMediaTypeSetDetails {
+  AudioSampleFormat sample_format;
   uint32 min_channels;
   uint32 max_channels;
   uint32 min_frames_per_second;
   uint32 max_frames_per_second;
 };
 
-// Sample formats for LPCM media types.
-enum LpcmSampleFormat {
-  // Placeholder indicating sample format is unknown.
-  UNKNOWN,
-
+enum AudioSampleFormat {
   // Placeholder indicating any sample format.
   ANY,
 
@@ -128,67 +90,15 @@ enum LpcmSampleFormat {
 
   // 24-bit signed samples in 32 bits, host-endian, sample size 4 bytes.
   // TODO(johngro): describe the packing for this
-  SIGNED_24_IN_32,  // Host endian
+  SIGNED_24_IN_32,
 
   // 32-bit floating-point samples, sample size 4 bytes.
   FLOAT,
 };
 
-// Media type details for the Multiplexed scheme.
-struct MultiplexedMediaTypeDetails {
-  // Describes how the streams are multiplexed.
-  MediaType multiplex_type;
-
-  // Media type for each substream.
-  array<MediaType> substream_types;
-};
-
-// Media type set details for the Multiplexed scheme.
-struct MultiplexedMediaTypeSetDetails {
-  // Describes how the streams can be multiplexed.
-  MediaTypeSet multiplex_type_set;
-
-  // Possible substream types.
-  array<MediaTypeSet> substream_type_sets;
-};
-
-// Audio encodings.
-// TODO(dalesat): Add more audio encodings.
-enum AudioEncoding {
-  // Placeholder indicating audio encoding is unknown.
-  UNKNOWN,
-
-  // Placeholder indicating any audio encoding.
-  ANY,
-
-  VORBIS,
-};
-
-// Media type details for the COMPRESSED_AUDIO scheme.
-struct CompressedAudioMediaTypeDetails {
-  AudioEncoding encoding;
-  LpcmSampleFormat sample_format;
-  uint32 channels;
-  uint32 frames_per_second;
-
-  // Encoding-specific parameter provided by demuxes and used by decoders.
-  string extra_data_base64;
-};
-
-// Media type set details for the COMPRESSED_AUDIO scheme.
-struct CompressedAudioMediaTypeSetDetails {
-  AudioEncoding encoding;
-  LpcmSampleFormat sample_format;
-  uint32 min_channels;
-  uint32 max_channels;
-  uint32 min_frames_per_second;
-  uint32 max_frames_per_second;
-};
-
-// Media type details for the VIDEO scheme.
-// TODO(dalesat): Expand and document.
+// Media type details for the VIDEO medium.
+// TODO(dalesat): Refine and document.
 struct VideoMediaTypeDetails {
-  VideoEncoding encoding;
   VideoProfile profile;
   PixelFormat pixel_format;
   ColorSpace color_space;
@@ -196,34 +106,17 @@ struct VideoMediaTypeDetails {
   uint32 height;
   uint32 coded_width;
   uint32 coded_height;
-
-  // Encoding-specific parameter provided by demuxes and used by decoders.
-  string extra_data_base64;
 };
 
-// Media type set details for the VIDEO scheme.
+// Media type set details for the VIDEO medium.
 // TODO(dalesat): Expand and document.
 struct VideoMediaTypeSetDetails {
-  VideoEncoding encoding;
   uint32 min_width;
   uint32 max_width;
   uint32 min_height;
   uint32 max_height;
 };
 
-// Video encodings.
-// TODO(dalesat): Add more video encodings.
-enum VideoEncoding {
-  // Placeholder indicating video encoding is unknown.
-  UNKNOWN,
-
-  // Placeholder indicating any video encoding.
-  ANY,
-
-  THEORA,
-  VP8,
-};
-
 // Video profiles.
 // TODO(dalesat): Blindly copied from Chromium, revisit.
 enum VideoProfile {
@@ -272,3 +165,23 @@ enum ColorSpace {
   HD_REC709,
   SD_REC601,
 };
+
+// Media type details for the TEXT medium.
+// TODO(dalesat): Define.
+struct TextMediaTypeDetails {
+};
+
+// Media type set details for the TEXT medium.
+// TODO(dalesat): Define.
+struct TextMediaTypeSetDetails {
+};
+
+// Media type details for the SUBPICTURE medium.
+// TODO(dalesat): Define.
+struct SubpictureMediaTypeDetails {
+};
+
+// Media type set details for the SUBPICTURE medium.
+// TODO(dalesat): Define.
+struct SubpictureMediaTypeSetDetails {
+};