Cleanup and reduce memory usage for MultiChannelResampler.

media/base/multi_channel_resampler.cc

Index: media/base/multi_channel_resampler.cc
diff --git a/media/base/multi_channel_resampler.cc b/media/base/multi_channel_resampler.cc
index a9aa8d68909fc2bcb238aeef715282d56cf0b50f..801e5344cf2bb4c6671a6fa883d91c947df19322 100644
--- a/media/base/multi_channel_resampler.cc
+++ b/media/base/multi_channel_resampler.cc
@@ -15,8 +15,8 @@ MultiChannelResampler::MultiChannelResampler(int channels,
                                              double io_sample_rate_ratio,
                                              size_t request_size,
                                              const ReadCB& read_cb)
-    : last_frame_count_(0),
-      read_cb_(read_cb),
+    : read_cb_(read_cb),
+      wrapped_resampler_audio_bus_(AudioBus::CreateWrapper(channels)),
       output_frames_ready_(0) {
   // Allocate each channel's resampler.
   resamplers_.reserve(channels);
@@ -25,6 +25,19 @@ MultiChannelResampler::MultiChannelResampler(int channels,
         io_sample_rate_ratio, request_size, base::Bind(
             &MultiChannelResampler::ProvideInput, base::Unretained(this), i)));
   }
+
+  // Setup the wrapped AudioBus for channel data.
+  wrapped_resampler_audio_bus_->set_frames(request_size);
+
+  // Allocate storage for all channels except the first, which will use the
+  // |destination| provided to ProvideInput() directly.
+  if (channels > 1) {
+    resampler_audio_bus_ = AudioBus::Create(channels - 1, request_size);
+    for (int i = 0; i < resampler_audio_bus_->channels(); ++i) {
+      wrapped_resampler_audio_bus_->SetChannelData(
+          i + 1, resampler_audio_bus_->channel(i));
+    }
+  }
 }
 
 MultiChannelResampler::~MultiChannelResampler() {}
@@ -72,40 +85,20 @@ void MultiChannelResampler::ProvideInput(int channel,
   // for it.  For subsequent channels, we can just dish out the channel data
   // from that (stored in |resampler_audio_bus_|).
   if (channel == 0) {
-    // Allocate staging arrays on the first request and if the frame size or
-    // |destination| changes (should only happen once).
-    if (!resampler_audio_bus_.get() ||
-        resampler_audio_bus_->frames() != frames ||
-        wrapped_resampler_audio_bus_->channel(0) != destination) {
-      resampler_audio_bus_ = AudioBus::Create(resamplers_.size(), frames);
-
-      // Create a channel vector based on |resampler_audio_bus_| but using
-      // |destination| directly for the first channel and then wrap it in a new
-      // AudioBus so we can avoid an extra memcpy later.
-      resampler_audio_data_.clear();
-      resampler_audio_data_.reserve(resampler_audio_bus_->channels());
-      resampler_audio_data_.push_back(destination);
-      for (int i = 1; i < resampler_audio_bus_->channels(); ++i)
-        resampler_audio_data_.push_back(resampler_audio_bus_->channel(i));
-      wrapped_resampler_audio_bus_ = AudioBus::WrapVector(
-          frames, resampler_audio_data_);
-    }
-
-    last_frame_count_ = frames;
+    wrapped_resampler_audio_bus_->SetChannelData(0, destination);
     read_cb_.Run(output_frames_ready_, wrapped_resampler_audio_bus_.get());
   } else {
     // All channels must ask for the same amount.  This should always be the
     // case, but let's just make sure.
-    DCHECK_EQ(frames, last_frame_count_);
+    DCHECK_EQ(frames, wrapped_resampler_audio_bus_->frames());
 
     // Copy the channel data from what we received from |read_cb_|.
-    memcpy(destination, resampler_audio_bus_->channel(channel),
-           sizeof(*resampler_audio_bus_->channel(channel)) * frames);
+    memcpy(destination, wrapped_resampler_audio_bus_->channel(channel),
+           sizeof(*wrapped_resampler_audio_bus_->channel(channel)) * frames);
   }
 }
 
 void MultiChannelResampler::Flush() {
-  last_frame_count_ = 0;
   for (size_t i = 0; i < resamplers_.size(); ++i)
     resamplers_[i]->Flush();
 }