Browser-wide audio mirroring for TabCapture API

media/audio/audio_parameters.h

 // Copyright (c) 2012 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.
 
 #ifndef MEDIA_AUDIO_AUDIO_PARAMETERS_H_
 #define MEDIA_AUDIO_AUDIO_PARAMETERS_H_
 
 #include "base/basictypes.h"
 #include "media/base/channel_layout.h"
 #include "media/base/media_export.h"
 
 namespace media {
 
 struct MEDIA_EXPORT AudioInputBufferParameters {
   double volume;
   uint32 size;
 };
 
 // Use a struct-in-struct approach to ensure that we can calculate the required
 // size as sizeof(AudioInputBufferParameters) + #(bytes in audio buffer) without
 // using packing.
 struct MEDIA_EXPORT AudioInputBuffer {
   AudioInputBufferParameters params;
   int8 audio[1];
 };
 
 class MEDIA_EXPORT AudioParameters {
  public:
   enum Format {

[miu, 2012/11/22 00:53:50]

Observation: Looks like this enum is polluted.  It doesn't just mean "format,"
but also "stream implementation."  Not sure how/whether to fix this.

Suggest you add a TODO comment for someone to rethink what the enum should be,
or if we need two enums, or other?

[justinlin, 2012/11/26 20:19:20]

Hmm, maybe Dale can comment on this?

[DaleCurtis, 2012/11/28 23:43:18]

Yeah, eventually this could be something like NORMAL, FAKE, VIRTUAL. It's grown
poorly in organic ways.

     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_LAST_FORMAT         // Only used for validation of format.
+    AUDIO_WEB_CONTENTS,       // Audio streams from a specific tab.

[miu, 2012/11/22 00:53:50]

Naming: Right now, this is browser-wide audio mirroring.  So, maybe name it
something like AUDIO_MIRROR_ALL?

[justinlin, 2012/11/26 20:19:20]

Done. How about AUDIO_MIRROR_BROWSER?

[DaleCurtis, 2012/11/28 23:43:18]

I think this is an odd name and if you plan to use this code in the future for
non-browser mirroring then it'd be worth keeping the name generic.
AUDIO_MIRRORING or AUDIO_VIRTUAL sounds better to me, but it's up to you.

[justinlin, 2012/11/29 10:08:33]

Let's stick with nouns: AUDIO_VIRTUAL.

+    AUDIO_LAST_FORMAT,        // Only used for validation of format.
   };
 
   enum {
     // Telephone quality sample rate, mostly for speech-only audio.
     kTelephoneSampleRate = 8000,
     // CD sampling rate is 44.1 KHz or conveniently 2x2x3x3x5x5x7x7.
     kAudioCDSampleRate = 44100,
   };
 
   AudioParameters();
@@ skipping 44 matching lines @@
   if (a.sample_rate() != b.sample_rate())
     return a.sample_rate() < b.sample_rate();
   if (a.bits_per_sample() != b.bits_per_sample())
     return a.bits_per_sample() < b.bits_per_sample();
   return a.frames_per_buffer() < b.frames_per_buffer();
 }
 
 }  // namespace media
 
 #endif  // MEDIA_AUDIO_AUDIO_PARAMETERS_H_