Added AudioBuffer/AudioChunk abstractions for speech recognition and improved speech_recognizer_impl_unittest.

audio_encoder  - Introduced AudioBuffer class in order to hide the current string-based implementation (which involved a lot of dirty and distributed casts) and make room for future implementations based on a circular buffer.

speech_recognizer_impl_unittest
 - Created MockAudioManager class, in order to avoid using the true audio manager on trybots, which could lead to errors accessing the audio device.

BUG=116954
TEST=speech_recognizer_impl_uinittest should never raise errors related to the audio driver (e.g, device in use, no microphone attached, etc).


Review URL: http://codereview.chromium.org/9646031

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@126512 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 91 insertions, 0 deletions

diff --git a/content/browser/speech/audio_buffer.cc b/content/browser/speech/audio_buffer.cc
new file mode 100644
index 0000000..5b887d7
--- /dev/null
+++ b/content/browser/speech/audio_buffer.cc
@@ -0,0 +1,91 @@
+// 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 "base/logging.h"
+#include "base/stl_util.h"
+#include "content/browser/speech/audio_buffer.h"
+
+namespace speech {
+
+AudioChunk::AudioChunk(int bytes_per_sample)
+    : bytes_per_sample_(bytes_per_sample) {
+}
+
+AudioChunk::AudioChunk(const uint8* data, size_t length, int bytes_per_sample)
+    : data_string_(reinterpret_cast<const char*>(data), length),
+      bytes_per_sample_(bytes_per_sample) {
+  DCHECK_EQ(length % bytes_per_sample, 0U);
+}
+
+bool AudioChunk::IsEmpty() const {
+  return data_string_.empty();
+}
+
+size_t AudioChunk::NumSamples() const {
+  return data_string_.size() / bytes_per_sample_;
+}
+
+const std::string& AudioChunk::AsString() const {
+  return data_string_;
+}
+
+int16 AudioChunk::GetSample16(size_t index) const {
+  DCHECK(index < (data_string_.size() / sizeof(int16)));
+  return SamplesData16()[index];
+}
+
+const int16* AudioChunk::SamplesData16() const {
+  return reinterpret_cast<const int16*>(data_string_.data());
+}
+
+
+AudioBuffer::AudioBuffer(int bytes_per_sample)
+    : bytes_per_sample_(bytes_per_sample) {
+  DCHECK(bytes_per_sample == 1 ||
+         bytes_per_sample == 2 ||
+         bytes_per_sample == 4);
+}
+
+AudioBuffer::~AudioBuffer() {
+  Clear();
+}
+
+void AudioBuffer::Enqueue(const uint8* data, size_t length) {
+  AudioChunk* chunk = new AudioChunk(data, length, bytes_per_sample_);
+  chunks_.push_back(chunk);
+}
+
+scoped_ptr<AudioChunk> AudioBuffer::DequeueSingleChunk() {
+  DCHECK(!chunks_.empty());
+  AudioChunk* chunk = *chunks_.begin();
+  chunks_.weak_erase(chunks_.begin());
+  return scoped_ptr<AudioChunk>(chunk);
+}
+
+scoped_ptr<AudioChunk> AudioBuffer::DequeueAll() {
+  AudioChunk* chunk = new AudioChunk(bytes_per_sample_);
+  size_t resulting_length = 0;
+  ChunksContainer::const_iterator it;
+  // In order to improve performance, calulate in advance the total length
+  // and then copy the chunks.
+  for (it = chunks_.begin(); it != chunks_.end(); ++it) {
+    resulting_length += (*it)->data_string_.length();
+  }
+  chunk->data_string_.reserve(resulting_length);
+  for (it = chunks_.begin(); it != chunks_.end(); ++it) {
+    chunk->data_string_.append((*it)->data_string_);
+  }
+  Clear();
+  return scoped_ptr<AudioChunk>(chunk);
+}
+
+void AudioBuffer::Clear() {
+  chunks_.erase(chunks_.begin(), chunks_.end());
+}
+
+bool AudioBuffer::IsEmpty() const {
+  return chunks_.empty();
+}
+
+}  // namespace speech