Add HE AAC support to ISO BMFF.

media/mp4/es_descriptor.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/mp4/es_descriptor.h"
+
+#include "media/base/bit_reader.h"
+#include "media/mp4/rcheck.h"
+
+// The elementary stream size is specific by up to 4 bytes.
+// The MSB of a byte indicates if there are more bytes for the size.
+static bool ReadESSize(media::BitReader* reader, uint32* size) {
+  uint8 msb;
+  uint8 byte;
+
+  *size = 0;
+
+  for (size_t i = 0; i < 4; ++i) {
+    RCHECK(reader->ReadBits(1, &msb));
+    RCHECK(reader->ReadBits(7, &byte));
+    *size = (*size << 7) + byte;
+
+    if (msb == 0)
+      break;
+  }
+
+  return true;
+}
+
+namespace media {
+
+namespace mp4 {
+
+ESDescriptor::ESDescriptor()
+    : object_type_(kForbidden) {
+}
+
+ESDescriptor::~ESDescriptor() {}
+
+bool ESDescriptor::Parse(const std::vector<uint8>& data) {
+  BitReader reader(&data[0], data.size());
+  uint8 tag;
+  uint32 size;
+  uint8 stream_dependency_flag;
+  uint8 url_flag;
+  uint8 ocr_stream_flag;
+
+  RCHECK(reader.ReadBits(8, &tag));
+  RCHECK(tag == kESDescrTag);
+  RCHECK(ReadESSize(&reader, &size));
+  RCHECK(static_cast<off_t>(size * CHAR_BIT) <= reader.NumBitsLeft());

[acolwell GONE FROM CHROMIUM, 2012/07/17 20:07:32]

Any reason not to use 8 instead of CHAR_BIT here and below?

[xiaomings, 2012/07/17 22:09:44]

Use 8 instead.

+
+  RCHECK(reader.SkipBits(16));  // ES_ID
+  RCHECK(reader.ReadBits(1, &stream_dependency_flag));
+  RCHECK(reader.ReadBits(1, &url_flag));
+  RCHECK(reader.ReadBits(1, &ocr_stream_flag));
+  RCHECK(reader.SkipBits(5));  // streamPriority
+
+  if (stream_dependency_flag)
+    reader.SkipBits(16);  // dependsOn_ES_ID;
+  RCHECK(!url_flag);  // We don't support url flag
+  if (ocr_stream_flag)
+    reader.SkipBits(16);  // OCR_ES_Id
+
+  RCHECK(ParseDecoderConfigDescriptor(&reader));
+
+  return true;
+}
+
+uint8 ESDescriptor::object_type() const {
+  return object_type_;
+}
+
+const std::vector<uint8>& ESDescriptor::decoder_specific_info() const {
+  return decoder_specific_info_;
+}
+
+bool ESDescriptor::ParseDecoderConfigDescriptor(BitReader* reader) {
+  uint8 tag;
+  uint32 size;
+
+  RCHECK(reader->ReadBits(8, &tag));
+  RCHECK(tag == kDecoderConfigDescrTag);
+  RCHECK(ReadESSize(reader, &size));
+  RCHECK(static_cast<off_t>(size * CHAR_BIT) <= reader->NumBitsLeft());
+
+  RCHECK(reader->ReadBits(8, &object_type_));
+  RCHECK(reader->SkipBits(96));
+  RCHECK(ParseDecoderSpecificInfo(reader));
+
+  return true;
+}
+
+bool ESDescriptor::ParseDecoderSpecificInfo(BitReader* reader) {
+  uint8 tag;
+  uint32 size;
+
+  RCHECK(reader->ReadBits(8, &tag));
+  RCHECK(tag == kDecoderSpecificInfoTag);
+  RCHECK(ReadESSize(reader, &size));
+  RCHECK(static_cast<off_t>(size * CHAR_BIT) <= reader->NumBitsLeft());
+
+  decoder_specific_info_.resize(size);
+  for (uint32 i = 0; i < size; ++i)
+    RCHECK(reader->ReadBits(8, &decoder_specific_info_[i]));
+
+  return true;
+}
+
+}  // namespace mp4
+
+}  // namespace media