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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 <stddef.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_t* size) {
- uint8_t msb;
- uint8_t 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_t object_type) {
- return object_type == kISO_14496_3 || object_type == kISO_13818_7_AAC_LC;
- }
- ESDescriptor::ESDescriptor()
- : object_type_(kForbidden) {
- }
- ESDescriptor::~ESDescriptor() = default;
- bool ESDescriptor::Parse(const std::vector<uint8_t>& data) {
- BitReader reader(&data[0], data.size());
- uint8_t tag;
- uint32_t size;
- uint8_t stream_dependency_flag;
- uint8_t url_flag;
- uint8_t ocr_stream_flag;
- uint16_t 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_t ESDescriptor::object_type() const {
- return object_type_;
- }
- const std::vector<uint8_t>& ESDescriptor::decoder_specific_info() const {
- return decoder_specific_info_;
- }
- bool ESDescriptor::ParseDecoderConfigDescriptor(BitReader* reader) {
- uint8_t tag;
- uint32_t size;
- uint64_t 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_t tag;
- uint32_t size;
- RCHECK(reader->ReadBits(8, &tag));
- RCHECK(tag == kDecoderSpecificInfoTag);
- RCHECK(ReadESSize(reader, &size));
- decoder_specific_info_.resize(size);
- for (uint32_t i = 0; i < size; ++i)
- RCHECK(reader->ReadBits(8, &decoder_specific_info_[i]));
- return true;
- }
- } // namespace mp4
- } // namespace media
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