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// Copyright 2014 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/formats/mp4/es_descriptor.h"
#include "media/base/bit_reader.h"
#include "media/formats/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 {
// static
bool ESDescriptor::IsAAC(uint8 object_type) {
return object_type == kISO_14496_3 || object_type == kISO_13818_7_AAC_LC;
}
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;
uint16 dummy;
RCHECK(reader.ReadBits(8, &tag));
RCHECK(tag == kESDescrTag);
RCHECK(ReadESSize(&reader, &size));
RCHECK(reader.ReadBits(16, &dummy)); // ES_ID
RCHECK(reader.ReadBits(1, &stream_dependency_flag));
RCHECK(reader.ReadBits(1, &url_flag));
RCHECK(!url_flag); // We don't support url flag
RCHECK(reader.ReadBits(1, &ocr_stream_flag));
RCHECK(reader.ReadBits(5, &dummy)); // streamPriority
if (stream_dependency_flag)
RCHECK(reader.ReadBits(16, &dummy)); // dependsOn_ES_ID
if (ocr_stream_flag)
RCHECK(reader.ReadBits(16, &dummy)); // 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;
uint64 dummy;
RCHECK(reader->ReadBits(8, &tag));
RCHECK(tag == kDecoderConfigDescrTag);
RCHECK(ReadESSize(reader, &size));
RCHECK(reader->ReadBits(8, &object_type_));
RCHECK(reader->ReadBits(64, &dummy));
RCHECK(reader->ReadBits(32, &dummy));
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));
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
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