Introduce AudioBus to replace std::vector<float*>.

media/base/audio_bus.cc

+// 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.
+
+#include "media/base/audio_bus.h"
+
+#include "base/logging.h"
+#include "base/memory/aligned_memory.h"
+#include "media/base/decrypt_config.h"
+
+namespace media {
+
+// Ensure each channel is 16-byte aligned for easy SSE optimizations.
+static const int kChannelAlignment = 16;
+
+AudioBus::AudioBus(int channels, int frames, ChannelLayout channel_layout)
+    : frames_(frames),
+      channel_layout_(channel_layout) {
+  // Choose a size such that each channel is aligned by kChannelAlignment.

[Chris Rogers, 2012/08/06 19:40:26]

do we want sanity checking DCHECKS, etc. on channels and frames (negative
values, wildly high values?)

[DaleCurtis, 2012/08/07 01:36:32]

Done.

+  int aligned_frames =
+      (frames_ + kChannelAlignment - 1) & ~(kChannelAlignment - 1);
+  audio_data_size_ = sizeof(float) * channels * aligned_frames;

[Chris Rogers, 2012/08/06 19:40:26]

The security guys seemed keen on using size_t for all of this kind of stuff:
http://trac.webkit.org/changeset/93749

Not sure if this is an issue, but you could talk with Chris Palmer...

Seems like we'd at least want sanity check for negative value if we're using
int...

[DaleCurtis, 2012/08/07 01:36:32]

Used CHECK() above plus limits to ensure this can't happen.

+
+  audio_data_.reset(static_cast<float*>(base::AlignedAlloc(
+      audio_data_size_, kChannelAlignment)));
+
+  // Seperate audio data out into channels for easy lookup later.

[Chris Rogers, 2012/08/06 19:40:26]

typo: Seperate

[DaleCurtis, 2012/08/07 01:36:32]

Done.

+  audio_data_vector_.reserve(channels);
+  for (int i = 0; i < channels; ++i)
+    audio_data_vector_.push_back(audio_data_.get() + i * aligned_frames);
+}
+
+AudioBus::AudioBus(int frames, const std::vector<float*>& audio_data_vector)
+    : audio_data_vector_(audio_data_vector),
+      frames_(frames),
+      channel_layout_(CHANNEL_LAYOUT_NONE) {
+  // Sanity check wrapped vector for alignment and channel count.
+  for (size_t i = 0; i < audio_data_vector_.size(); ++i) {
+    DCHECK_EQ(reinterpret_cast<uintptr_t>(audio_data_vector_[i]) &

[scherkus (not reviewing), 2012/08/06 18:55:34]

idea: add static IsAligned() function at top by constant for a more readable
DCHECK

[DaleCurtis, 2012/08/07 01:36:32]

Done.

+              (kChannelAlignment - 1), 0U);
+  }
+}
+
+AudioBus::~AudioBus() {}
+
+scoped_ptr<AudioBus> AudioBus::Create(int channels, int frames) {
+  return scoped_ptr<AudioBus>(new AudioBus(
+      channels, frames, CHANNEL_LAYOUT_NONE));
+}
+
+scoped_ptr<AudioBus> AudioBus::Create(const AudioParameters& params) {
+  return scoped_ptr<AudioBus>(new AudioBus(
+      params.channels(), params.frames_per_buffer(), params.channel_layout()));
+}
+
+scoped_ptr<AudioBus> AudioBus::WrapVector(
+    int frames, const std::vector<float*>& audio_data_vector) {
+  return scoped_ptr<AudioBus>(new AudioBus(frames, audio_data_vector));
+}
+
+void AudioBus::Zero(int frames) {
+  DCHECK_LE(frames, frames_);
+  for (size_t i = 0; i < audio_data_vector_.size(); ++i)
+    memset(audio_data_vector_[i], 0, frames * sizeof(*audio_data_vector_[i]));
+}
+
+}  // namespace media