118 lines
2.8 KiB
C++
118 lines
2.8 KiB
C++
// Copyright (c) 2012 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#include "media/mp4/es_descriptor.h"
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#include "media/base/bit_reader.h"
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#include "media/mp4/rcheck.h"
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// The elementary stream size is specific by up to 4 bytes.
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// The MSB of a byte indicates if there are more bytes for the size.
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static bool ReadESSize(media::BitReader* reader, uint32* size) {
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uint8 msb;
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uint8 byte;
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*size = 0;
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for (size_t i = 0; i < 4; ++i) {
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RCHECK(reader->ReadBits(1, &msb));
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RCHECK(reader->ReadBits(7, &byte));
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*size = (*size << 7) + byte;
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if (msb == 0)
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break;
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}
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return true;
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}
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namespace media {
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namespace mp4 {
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// static
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bool ESDescriptor::IsAAC(ObjectType object_type) {
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return object_type == kISO_14496_3 || object_type == kISO_13818_7_AAC_LC;
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}
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ESDescriptor::ESDescriptor()
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: object_type_(kForbidden) {
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}
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ESDescriptor::~ESDescriptor() {}
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bool ESDescriptor::Parse(const std::vector<uint8>& data) {
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BitReader reader(&data[0], data.size());
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uint8 tag;
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uint32 size;
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uint8 stream_dependency_flag;
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uint8 url_flag;
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uint8 ocr_stream_flag;
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uint16 dummy;
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RCHECK(reader.ReadBits(8, &tag));
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RCHECK(tag == kESDescrTag);
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RCHECK(ReadESSize(&reader, &size));
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RCHECK(reader.ReadBits(16, &dummy)); // ES_ID
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RCHECK(reader.ReadBits(1, &stream_dependency_flag));
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RCHECK(reader.ReadBits(1, &url_flag));
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RCHECK(!url_flag); // We don't support url flag
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RCHECK(reader.ReadBits(1, &ocr_stream_flag));
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RCHECK(reader.ReadBits(5, &dummy)); // streamPriority
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if (stream_dependency_flag)
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RCHECK(reader.ReadBits(16, &dummy)); // dependsOn_ES_ID
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if (ocr_stream_flag)
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RCHECK(reader.ReadBits(16, &dummy)); // OCR_ES_Id
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RCHECK(ParseDecoderConfigDescriptor(&reader));
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return true;
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}
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ObjectType ESDescriptor::object_type() const {
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return object_type_;
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}
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const std::vector<uint8>& ESDescriptor::decoder_specific_info() const {
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return decoder_specific_info_;
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}
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bool ESDescriptor::ParseDecoderConfigDescriptor(BitReader* reader) {
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uint8 tag;
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uint32 size;
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uint64 dummy;
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RCHECK(reader->ReadBits(8, &tag));
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RCHECK(tag == kDecoderConfigDescrTag);
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RCHECK(ReadESSize(reader, &size));
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RCHECK(reader->ReadBits(8, &object_type_));
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RCHECK(reader->ReadBits(64, &dummy));
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RCHECK(reader->ReadBits(32, &dummy));
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RCHECK(ParseDecoderSpecificInfo(reader));
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return true;
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}
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bool ESDescriptor::ParseDecoderSpecificInfo(BitReader* reader) {
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uint8 tag;
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uint32 size;
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RCHECK(reader->ReadBits(8, &tag));
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RCHECK(tag == kDecoderSpecificInfoTag);
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RCHECK(ReadESSize(reader, &size));
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decoder_specific_info_.resize(size);
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for (uint32 i = 0; i < size; ++i)
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RCHECK(reader->ReadBits(8, &decoder_specific_info_[i]));
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return true;
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}
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} // namespace mp4
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} // namespace media
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