Add HE AAC support to ISO BMFF.

media/mp4/aac.h

+// 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.
+
+#ifndef MEDIA_MP4_AAC_H_
+#define MEDIA_MP4_AAC_H_
+
+#include <vector>
+
+#include "base/basictypes.h"
+#include "media/base/channel_layout.h"
+#include "media/base/media_export.h"
+
+namespace media {
+
+class BitReader;
+
+namespace mp4 {
+
+// This class parses the AAC information from decoder specific information
+// embedded in the esds box in an ISO BMFF file.
+// Please refer to ISO 14496 Part 3 Table 1.13 - Syntax of AudioSpecificConfig
+// for more details.
+class MEDIA_EXPORT AAC {
+ public:
+  AAC();
+  ~AAC();
+
+  // Parse the AAC config from the raw binary data embedded in esds box.
+  // The function will parse the data and get the ElementaryStreamDescriptor,
+  // then it will parse the ElementaryStreamDescriptor to get audio stream
+  // configurations.
+  bool Parse(const std::vector<uint8>& data);
+
+  uint32 frequency() const;
+  ChannelLayout channel_layout() const;
+
+  // This function converts a raw AAC frame into an AAC frame with an ADTS
+  // header. On success, the function returns true and stores the converted data
+  // in the buffer. The function returns false on failure and leaves the buffer
+  // unchanged.
+  bool ConvertEsdsToADTS(std::vector<uint8>* buffer) const;
+
+ private:
+  bool SkipDecoderGASpecificConfig(BitReader* bit_reader) const;
+  bool SkipErrorSpecificConfig() const;
+  bool SkipGASpecificConfig(BitReader* bit_reader) const;
+
+  // The following variables store the AAC specific configuration information
+  // that are used to generate the ADTS header.
+  uint8 profile_;
+  uint8 frequency_index_;
+  uint8 channel_config_;
+
+  // The following variables store audio configuration information that
+  // can be used by Chromium. They are based on the AAC specific
+  // configuration but can be overridden by extensions in elementary
+  // stream descriptor.
+  uint32 frequency_;
+  ChannelLayout channel_layout_;
+};
+
+}  // namespace mp4
+
+}  // namespace media
+
+#endif  // MEDIA_MP4_AAC_H_