Audio software mixer.

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"
@@ skipping 14 matching lines @@
   };
 
   // Telephone quality sample rate, mostly for speech-only audio.
   static const uint32 kTelephoneSampleRate = 8000;
   // CD sampling rate is 44.1 KHz or conveniently 2x2x3x3x5x5x7x7.
   static const uint32 kAudioCDSampleRate = 44100;
   // Digital Audio Tape sample rate.
   static const uint32 kAudioDATSampleRate = 48000;
 
   AudioParameters();
-  AudioParameters(Format format, ChannelLayout channel_layout,
-                  int sample_rate, int bits_per_sample,
+  AudioParameters(Format format,
+                  bool use_browser_mixer,

[scherkus (not reviewing), 2012/03/27 14:34:19]

Is the only reason to have programmatic control over using the mixer is to let
certain clients opt out of using the mixer?

Given we're developing this behind a flag I don't see a reason to include this
until we've proven that the mixer isn't a good fit for those clients. In other
words, reverse the logic and have the flag *enable* the mixer for *all* clients.

That way it stays off by default, the media team can test with it on, fix bugs +
analyze performance, then turn it on by default. If everything works as intended
then there'll be no need to for use_browser_mixer at all.

[enal1, 2012/03/27 15:12:01]

yes, not having that flag is very lukrative suggestion. Among other things it
will drastically reduce amount of changed files.

Unfortunately, there are strong arguments for that flag as well. Main argument
is that it will allow per-client switch to the mixer, as developers for some
clients feel their clients don't need mixer.

Chris was very happy with that flag...

On 2012/03/27 14:34:19, scherkus wrote:

[scherkus (not reviewing), 2012/03/27 15:17:06]

They are arguments that aren't based on any real world data or analysis.

[enal1, 2012/03/27 15:34:08]

Arguments are "my code right now works reasonable, I have lot of my own things
to do, so please don't create me new issues. You need something -- please do it,
and when it works reasonable you can switch my code to it, but don't create any
problems for me right now".

I'd say that is reasonable attitude, and peace between groups may be worth extra
(temporary) code complexity.

On 2012/03/27 15:17:06, scherkus wrote:

+                  ChannelLayout channel_layout,
+                  int sample_rate,
+                  int bits_per_sample,
                   int frames_per_buffer);
-  void Reset(Format format, ChannelLayout channel_layout,
-             int sample_rate, int bits_per_sample,
+  void Reset(Format format,
+             bool use_browser_mixer,
+             ChannelLayout channel_layout,
+             int sample_rate,
+             int bits_per_sample,
              int frames_per_buffer);
 
   // Checks that all values are in the expected range. All limits are specified
   // in media::Limits.
   bool IsValid() const;
 
   // Returns size of audio buffer in bytes.
   int GetBytesPerBuffer() const;
 
   // Returns the number of bytes representing one second of audio.
   int GetBytesPerSecond() const;
 
   // Returns the number of bytes representing a frame of audio.
   int GetBytesPerFrame() const;
 
   Format format() const { return format_; }
   ChannelLayout channel_layout() const { return channel_layout_; }
   int sample_rate() const { return sample_rate_; }
   int bits_per_sample() const { return bits_per_sample_; }
   int frames_per_buffer() const { return frames_per_buffer_; }
   int channels() const { return channels_; }
+  bool use_browser_mixer() const { return use_browser_mixer_; }
 
  private:
   Format format_;                 // Format of the stream.
+  bool use_browser_mixer_;        // Should we use browser-side or operating
+                                  // system audio mixer.
   ChannelLayout channel_layout_;  // Order of surround sound channels.
   int sample_rate_;               // Sampling frequency/rate.
   int bits_per_sample_;           // Number of bits per sample.
   int frames_per_buffer_;         // Number of frames in a buffer.
 
   int channels_;                  // Number of channels. Value set based on
                                   // |channel_layout|.
 };
 
 #endif  // MEDIA_AUDIO_AUDIO_PARAMETERS_H_