Adds Analog Gain Control (AGC) to the WebRTC client.

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"
 
+#pragma pack(push, 1)

[tommi (sloooow) - chröme, 2012/03/16 13:31:05]

Can you add a note why we set the packing to 1?

Actually, since we intend to use this only for shared memory and not for network
buffers, I wonder if we can solve the problem of calculating the buffer size in
a different way.

I know that the problem is that with default 32bit packing, sizeof  the |audio|
member will be 4 (not 1) and that messes up the calculation for
kSizeOfStructMinusArr (which I think should be named kSizeOfStructMinusPacket
but maybe we don't need it...).

So, how about this approach instead:

struct MEDIA_EXPORT AudioInputBufferParameters {
  double volume;
  uint32 size;
};

struct MEDIA_EXPORT AudioInputBuffer {
  AudioInputBufferParameters params;
  int8 audio[1];
};

and then instead of kSizeOfStructMinusArr, we'll use
sizeof(AudioInputBufferParameters).  WDYT?

oh, and if we do it that way, can you add comments on why we separate the
parameters from the data based on the above.

[henrika (OOO until Aug 14), 2012/03/21 10:16:04]

Done.

+struct MEDIA_EXPORT AudioInputBuffer {
+  double volume;
+  uint32 size;
+  int8 audio[1];
+
+  static const int kSizeOfStructMinusArr;
+};
+#pragma pack(pop)
+
 // TODO(vrk): This should probably be changed to an immutable object instead of
 // a struct. See crbug.com/115902.
 struct MEDIA_EXPORT AudioParameters {
   // Compare is useful when AudioParameters is used as a key in std::map.
   class MEDIA_EXPORT Compare {
    public:
     bool operator()(const AudioParameters& a, const AudioParameters& b) const;
   };
 
   enum Format {
@@ skipping 28 matching lines @@
   ChannelLayout channel_layout;  // Order of surround sound channels.
   int sample_rate;               // Sampling frequency/rate.
   int bits_per_sample;           // Number of bits per sample.
   int samples_per_packet;        // Size of a packet in frames.
 
   int channels;                  // Number of channels. Value set based on
                                  // |channel_layout|.
 };
 
 #endif  // MEDIA_AUDIO_AUDIO_PARAMETERS_H_