Audio software mixer.

media/audio/audio_parameters.h

Index: media/audio/audio_parameters.h
===================================================================
--- media/audio/audio_parameters.h	(revision 128216)
+++ media/audio/audio_parameters.h	(working copy)
@@ -32,11 +32,17 @@
   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
@@ -58,9 +64,12 @@
   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.