(Committing on behalf of Chris Rogers -- original CL...

webkit/glue/media/audio_decoder.cc

+// Copyright (c) 2010 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 "webkit/glue/media/audio_decoder.h"
+
+#include <vector>
+#include "base/basictypes.h"
+#include "base/string_util.h"
+#include "base/time.h"
+#include "media/filters/audio_file_reader.h"
+#include "third_party/WebKit/WebKit/chromium/public/WebAudioBus.h"
+
+using media::AudioFileReader;
+using media::InMemoryDataReader;
+using std::vector;
+using WebKit::WebAudioBus;
+
+namespace webkit_glue {
+
+// Decode in-memory audio file data.
+bool DecodeAudioFileData(
+    WebKit::WebAudioBus* destination_bus,
+    const char* data, size_t data_size, double sample_rate) {
+  DCHECK(destination_bus);
+  if (!destination_bus)
+    return false;
+
+  // Uses the FFmpeg library for audio file reading.
+  InMemoryDataReader data_reader(data, data_size);
+  AudioFileReader reader(&data_reader);
+
+  if (!reader.Open())
+    return false;
+
+  size_t number_of_channels = reader.channels();
+  double file_sample_rate = reader.sample_rate();
+  double duration = reader.duration().InSecondsF();
+  size_t number_of_frames = static_cast<size_t>(reader.number_of_frames());
+
+  // TODO(crogers) : do sample-rate conversion with FFmpeg.
+  // For now, we're ignoring the requested 'sample_rate' and returning
+  // the WebAudioBus at the file's sample-rate.
+  // double destination_sample_rate =
+  //   (sample_rate != 0.0) ? sample_rate : file_sample_rate;
+  double destination_sample_rate = file_sample_rate;
+
+  DLOG(INFO) << "Decoding file data -"
+      << " data: " << data
+      << " data size: " << data_size
+      << " duration: " << duration
+      << " number of frames: " << number_of_frames
+      << " sample rate: " << file_sample_rate
+      << " number of channels: " << number_of_channels;
+
+  // Change to destination sample-rate.
+  number_of_frames = static_cast<size_t>(number_of_frames *
+      (destination_sample_rate / file_sample_rate));
+
+  // Allocate and configure the output audio channel data.
+  destination_bus->initialize(number_of_channels,
+                              number_of_frames,
+                              destination_sample_rate);
+
+  // Wrap the channel pointers which will receive the decoded PCM audio.
+  vector<float*> audio_data;
+  audio_data.reserve(number_of_channels);
+  for (size_t i = 0; i < number_of_channels; ++i) {
+    audio_data.push_back(destination_bus->channelData(i));
+  }
+
+  // Decode the audio file data.
+  return reader.Read(audio_data, number_of_frames);
+}
+
+}  // namespace webkit_glue