Mojo interfaces needed for switching audio rendering stream creation and closing from IPC to Mojo

media/mojo/interfaces/audio_output.mojom

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+module content.mojom;
+
+struct AudioOutputStreamParameters {
+
+  enum Format {
+    AUDIO_PCM_LINEAR = 0,            // PCM is 'raw' amplitude samples.
+    AUDIO_PCM_LOW_LATENCY,           // Linear PCM, low latency requested.
+    AUDIO_FAKE,                      // Creates a fake AudioOutputStream object.
+    AUDIO_FORMAT_LAST = AUDIO_FAKE,  // Only used for validation of format.
+  };
+
+  // Enumerates the various representations of the ordering of audio channels.
+  // Logged to UMA, so never reuse a value, always add new/greater ones!
+  enum ChannelLayout {
+    CHANNEL_LAYOUT_NONE = 0,
+    CHANNEL_LAYOUT_UNSUPPORTED = 1,
+
+    // Front C
+    CHANNEL_LAYOUT_MONO = 2,
+
+    // Front L, Front R
+    CHANNEL_LAYOUT_STEREO = 3,
+
+    // Front L, Front R, Back C
+    CHANNEL_LAYOUT_2_1 = 4,
+
+    // Front L, Front R, Front C
+    CHANNEL_LAYOUT_SURROUND = 5,
+
+    // Front L, Front R, Front C, Back C
+    CHANNEL_LAYOUT_4_0 = 6,
+
+    // Front L, Front R, Side L, Side R
+    CHANNEL_LAYOUT_2_2 = 7,
+
+    // Front L, Front R, Back L, Back R
+    CHANNEL_LAYOUT_QUAD = 8,
+
+    // Front L, Front R, Front C, Side L, Side R
+    CHANNEL_LAYOUT_5_0 = 9,
+
+    // Front L, Front R, Front C, LFE, Side L, Side R
+    CHANNEL_LAYOUT_5_1 = 10,
+
+    // Front L, Front R, Front C, Back L, Back R
+    CHANNEL_LAYOUT_5_0_BACK = 11,
+
+    // Front L, Front R, Front C, LFE, Back L, Back R
+    CHANNEL_LAYOUT_5_1_BACK = 12,
+
+    // Front L, Front R, Front C, Side L, Side R, Back L, Back R
+    CHANNEL_LAYOUT_7_0 = 13,
+
+    // Front L, Front R, Front C, LFE, Side L, Side R, Back L, Back R
+    CHANNEL_LAYOUT_7_1 = 14,
+
+    // Front L, Front R, Front C, LFE, Side L, Side R, Front LofC, Front RofC
+    CHANNEL_LAYOUT_7_1_WIDE = 15,
+
+    // Stereo L, Stereo R
+    CHANNEL_LAYOUT_STEREO_DOWNMIX = 16,
+
+    // Stereo L, Stereo R, LFE
+    CHANNEL_LAYOUT_2POINT1 = 17,
+
+    // Stereo L, Stereo R, Front C, LFE
+    CHANNEL_LAYOUT_3_1 = 18,
+
+    // Stereo L, Stereo R, Front C, Rear C, LFE
+    CHANNEL_LAYOUT_4_1 = 19,
+
+    // Stereo L, Stereo R, Front C, Side L, Side R, Back C
+    CHANNEL_LAYOUT_6_0 = 20,
+
+    // Stereo L, Stereo R, Side L, Side R, Front LofC, Front RofC
+    CHANNEL_LAYOUT_6_0_FRONT = 21,
+
+    // Stereo L, Stereo R, Front C, Rear L, Rear R, Rear C
+    CHANNEL_LAYOUT_HEXAGONAL = 22,
+
+    // Stereo L, Stereo R, Front C, LFE, Side L, Side R, Rear Center
+    CHANNEL_LAYOUT_6_1 = 23,
+
+    // Stereo L, Stereo R, Front C, LFE, Back L, Back R, Rear Center
+    CHANNEL_LAYOUT_6_1_BACK = 24,
+
+    // Stereo L, Stereo R, Side L, Side R, Front LofC, Front RofC, LFE
+    CHANNEL_LAYOUT_6_1_FRONT = 25,
+
+    // Front L, Front R, Front C, Side L, Side R, Front LofC, Front RofC
+    CHANNEL_LAYOUT_7_0_FRONT = 26,
+
+    // Front L, Front R, Front C, LFE, Back L, Back R, Front LofC, Front RofC
+    CHANNEL_LAYOUT_7_1_WIDE_BACK = 27,
+
+    // Front L, Front R, Front C, Side L, Side R, Rear L, Back R, Back C.
+    CHANNEL_LAYOUT_OCTAGONAL = 28,
+
+    // Channels are not explicitly mapped to speakers.
+    CHANNEL_LAYOUT_DISCRETE = 29,
+
+    // Front L, Front R, Front C. Front C contains the keyboard mic audio. This
+    // layout is only intended for input for WebRTC. The Front C channel
+    // is stripped away in the WebRTC audio input pipeline and never seen outside

[Henrik Grunell, 2016/04/19 15:36:08]

Nit: 80 chars.

[rchtara, 2016/04/21 09:10:17]

Done.

+    // of that.
+    CHANNEL_LAYOUT_STEREO_AND_KEYBOARD_MIC = 30,
+
+    // Front L, Front R, Side L, Side R, LFE
+    CHANNEL_LAYOUT_4_1_QUAD_SIDE = 31,
+
+    // Max value, must always equal the largest entry ever logged.
+    CHANNEL_LAYOUT_MAX = CHANNEL_LAYOUT_4_1_QUAD_SIDE
+  };
+
+
+  Format format_;                 // Format of the stream.
+  ChannelLayout channel_layout_;  // Order of surround sound channels.
+  int32 channels_;                  // Number of channels. Value set based on

[Henrik Grunell, 2016/04/19 15:36:08]

Align the comments.

[rchtara, 2016/04/21 09:10:17]

Done.

+                                  // |channel_layout|.
+  int32 sample_rate_;               // Sampling frequency/rate.
+  int32 bits_per_sample_;           // Number of bits per sample.
+  int32 frames_per_buffer_;         // Number of frames in a buffer.
+  int32 effects_;                   // Bitmask using PlatformEffectsMask.
+
+};
+
+// Used on the renderer side.

[Henrik Grunell, 2016/04/19 15:36:08]

Remove this comment and same below. The interface is general and should not care
about processes etc. (I had that comment (I think) in the proposal just to point
out how it will be used.)

[rchtara, 2016/04/21 09:10:17]

Acknowledged.

+interface AudioOutputStream {
+  Close();

[Henrik Grunell, 2016/04/19 15:36:08]

Did you look into if it's possible to use delete/unbind of the object as a way
to notify the service that it should be closed?

[rchtara, 2016/04/21 09:10:17]

yes, I did. but as you probably remember, we decided to keep that to report
errors from the browser to renderer as it's harder to do. 

+};
+
+// Used on the renderer side.
+interface AudioOutput {
+  CreateStream(
+      int32 stream_id_,

[Henrik Grunell, 2016/04/19 15:36:08]

Add a comment (before CreateStream) and explain why the stream_id is needed.

[Henrik Grunell, 2016/04/19 15:36:08]

No trailing _ in these variables.

[rchtara, 2016/04/21 09:10:17]

Done.

[rchtara, 2016/04/21 09:10:17]

Done.

+      int32 render_frame_id_,
+      AudioOutputStreamParameters params) =>
+      (AudioOutputStream? stream,
+       int32 stream_id,

[Henrik Grunell, 2016/04/19 15:36:08]

Put stream_id first.

[rchtara, 2016/04/21 09:10:17]

Done.

+       handle<shared_buffer>? shared_buffer,
+       handle? socket_descriptor);
+};