AudioBus: Add a ToInterleavedFloat() method to AudioBus

media/cast/sender/audio_encoder.cc

 // Copyright 2014 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.
 
 #include "media/cast/sender/audio_encoder.h"
 
 #include <stdint.h>
 
 #include <algorithm>
 #include <limits>
@@ skipping 265 matching lines @@
              OPUS_OK);
   }
 
  private:
   ~OpusImpl() final {}
 
   void TransferSamplesIntoBuffer(const AudioBus* audio_bus,
                                  int source_offset,
                                  int buffer_fill_offset,
                                  int num_samples) final {
+    DCHECK_EQ(audio_bus->channels(), num_channels_);

[mcasas, 2016/04/11 23:47:08]

nit: Expected value goes first, and I 
think in this case that's |num_channels_|.

     // Opus requires channel-interleaved samples in a single array.
-    for (int ch = 0; ch < audio_bus->channels(); ++ch) {
-      const float* src = audio_bus->channel(ch) + source_offset;
-      const float* const src_end = src + num_samples;
-      float* dest = buffer_.get() + buffer_fill_offset * num_channels_ + ch;
-      for (; src < src_end; ++src, dest += num_channels_)
-        *dest = *src;
-    }
+    audio_bus->ToInterleavedFloat(source_offset,
+                                  buffer_fill_offset * num_channels_,
+                                  num_samples, buffer_.get());
   }
 
   bool EncodeFromFilledBuffer(std::string* out) final {
     out->resize(kOpusMaxPayloadSize);
     const opus_int32 result = opus_encode_float(
         opus_encoder_, buffer_.get(), samples_per_frame_,
         reinterpret_cast<uint8_t*>(string_as_array(out)), kOpusMaxPayloadSize);
     if (result > 1) {
       out->resize(result);
       return true;
@@ skipping 564 matching lines @@
   cast_environment_->PostTask(CastEnvironment::AUDIO,
                               FROM_HERE,
                               base::Bind(&AudioEncoder::ImplBase::EncodeAudio,
                                          impl_,
                                          base::Passed(&audio_bus),
                                          recorded_time));
 }
 
 }  // namespace cast
 }  // namespace media