Strip away the keyboard mic channel if no audio processing.

content/renderer/media/media_stream_audio_processor.cc

Index: content/renderer/media/media_stream_audio_processor.cc
diff --git a/content/renderer/media/media_stream_audio_processor.cc b/content/renderer/media/media_stream_audio_processor.cc
index ac41187c832214d49f44e0a759d87c07361b6d8e..6dfe6b04e7365114e2ca49b16f19fe5880bf0e8f 100644
--- a/content/renderer/media/media_stream_audio_processor.cc
+++ b/content/renderer/media/media_stream_audio_processor.cc
@@ -227,7 +227,22 @@ void MediaStreamAudioProcessor::PushCaptureData(
     const media::AudioBus* audio_source) {
   DCHECK(capture_thread_checker_.CalledOnValidThread());
 
-  capture_fifo_->Push(audio_source);
+  // If we don't use audio processing we strip any keyboard mic channel before
+  // putting it in the fifo.
+  if (input_format_.channel_layout() ==

[no longer working on chromium, 2014/09/24 12:41:27]

you should move these code to MediaStreamAudioFifo

[Henrik Grunell, 2014/09/24 20:01:29]

Yep, but I need the additional info about layout and audio processing enabled.

[Henrik Grunell, 2014/09/26 10:04:27]

Changed to what I proposed offline: take source and destination channels in the
fifo ctor, use that info to possibly strip away channels.

+          media::CHANNEL_LAYOUT_STEREO_AND_KEYBOARD_MIC &&
+      !audio_processing_) {
+    scoped_ptr<media::AudioBus> audio_source_stereo =

[no longer working on chromium, 2014/09/24 12:41:27]

use a member in MediaStreamAudioFifo, and set it up when MediaStreamAudioFifo is
created.

[Henrik Grunell, 2014/09/26 10:04:27]

Done.

+        media::AudioBus::CreateWrapper(2);
+    audio_source_stereo->SetChannelData(
+        0, const_cast<float*>(audio_source->channel(0)));
+    audio_source_stereo->SetChannelData(
+        1, const_cast<float*>(audio_source->channel(1)));
+    audio_source_stereo->set_frames(audio_source->frames());
+    capture_fifo_->Push(audio_source_stereo.get());
+  } else {
+    capture_fifo_->Push(audio_source);
+  }
 }
 
 bool MediaStreamAudioProcessor::ProcessAndConsumeData(
@@ -466,7 +481,7 @@ void MediaStreamAudioProcessor::InitializeCaptureFifo(
   // format it would prefer.
   const int output_sample_rate = audio_processing_ ?
       kAudioProcessingSampleRate : input_format.sample_rate();
-  const media::ChannelLayout output_channel_layout = audio_processing_ ?
+  media::ChannelLayout output_channel_layout = audio_processing_ ?
       media::GuessChannelLayout(kAudioProcessingNumberOfChannels) :
       input_format.channel_layout();

[no longer working on chromium, 2014/09/24 12:41:27]

can the output_channel_layout be media::CHANNEL_LAYOUT_STEREO_AND_KEYBOARD_MIC
at all?

[Henrik Grunell, 2014/09/24 20:01:29]

No.

 
@@ -487,6 +502,19 @@ void MediaStreamAudioProcessor::InitializeCaptureFifo(
     output_frames = processing_frames;
   }
 
+  int capture_fifo_channels = input_format.channels();
+
+  // Special cases for if we have a keyboard mic channel on the input and no
+  // audio processing is used. We will then strip away that channel before
+  // putting it in the fifo. We keep the layout in |input_format_| since that's
+  // what we expect as input to this class.
+  if (input_format.channel_layout() ==
+          media::CHANNEL_LAYOUT_STEREO_AND_KEYBOARD_MIC &&
+      !audio_processing_) {
+    capture_fifo_channels = 2;
+    output_channel_layout = media::CHANNEL_LAYOUT_STEREO;
+  }
+
   output_format_ = media::AudioParameters(
       media::AudioParameters::AUDIO_PCM_LOW_LATENCY,
       output_channel_layout,
@@ -495,7 +523,7 @@ void MediaStreamAudioProcessor::InitializeCaptureFifo(
       output_frames);
 
   capture_fifo_.reset(
-      new MediaStreamAudioFifo(input_format.channels(),
+      new MediaStreamAudioFifo(capture_fifo_channels,

[no longer working on chromium, 2014/09/24 12:41:27]

how about modify MediaStreamAudioFifo constructor and inject a boolean there to
indicate if audio processing is enabled or not, then all these channel layout
things will be handled internally in MediaStreamAudioFifo.

[Henrik Grunell, 2014/09/24 20:01:29]

Yes, but the fifo would need to know about the layout, since we can have 3
channels in other layouts as well.

                                input_format.frames_per_buffer(),
                                processing_frames));