Make sure AudioBufferConverter uses aligned AudioBus channels.

media/base/audio_buffer_converter.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/base/audio_buffer_converter.h"
 
 #include <cmath>
 
 #include "base/logging.h"
 #include "media/base/audio_buffer.h"
@@ skipping 180 matching lines @@
                                 output_params_.sample_rate(),
                                 request_frames);
   scoped_ptr<AudioBus> output_bus =
       AudioBus::CreateWrapper(output_buffer->channel_count());
 
   int frames_remaining = request_frames;
 
   // The AudioConverter wants requests of a fixed size, so we'll slide an
   // AudioBus of that size across the |output_buffer|.
   while (frames_remaining != 0) {
-    int frames_this_iteration =
-        std::min(output_params_.frames_per_buffer(), frames_remaining);
-
-    int offset_into_buffer = output_buffer->frame_count() - frames_remaining;
+    // It's important that this is a multiple of AudioBus::kChannelAlignment in
+    // all requests except for the last, otherwise downstream SIMD optimizations
+    // will crash on unaligned data.
+    const int frames_this_iteration = std::min(
+        static_cast<int>(SincResampler::kDefaultRequestSize), frames_remaining);
+    const int offset_into_buffer =
+        output_buffer->frame_count() - frames_remaining;
 
     // Wrap the portion of the AudioBuffer in an AudioBus so the AudioConverter
     // can fill it.
     output_bus->set_frames(frames_this_iteration);
     for (int ch = 0; ch < output_buffer->channel_count(); ++ch) {
       output_bus->SetChannelData(
           ch,
           reinterpret_cast<float*>(output_buffer->channel_data()[ch]) +
               offset_into_buffer);
     }
@@ skipping 21 matching lines @@
   is_flushing_ = false;
   audio_converter_->Reset();
   DCHECK_EQ(input_frames_, 0);
   DCHECK_EQ(last_input_buffer_offset_, 0);
   DCHECK_LT(buffered_input_frames_, 1.0);
   DCHECK(queued_inputs_.empty());
   buffered_input_frames_ = 0.0;
 }
 
 }  // namespace media