// Copyright 2023 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "media/parsers/h266_nalu_parser.h"
#include <stddef.h>
#include <algorithm>
#include <cmath>
#include <cstring>
#include "base/logging.h"
#include "media/base/decrypt_config.h"
#include "media/parsers/bit_reader_macros.h"
namespace media {
H266NALU::H266NALU() {
memset(reinterpret_cast<void*>(this), 0, sizeof(*this));
}
H266NaluParser::H266NaluParser() {
Reset();
}
H266NaluParser::~H266NaluParser() = default;
void H266NaluParser::Reset() {
stream_ = nullptr;
bytes_left_ = 0;
encrypted_ranges_.clear();
previous_nalu_range_.clear();
}
void H266NaluParser::SetStream(const uint8_t* stream, off_t stream_size) {
std::vector<SubsampleEntry> subsamples;
SetEncryptedStream(stream, stream_size, subsamples);
}
void H266NaluParser::SetEncryptedStream(
const uint8_t* stream,
off_t stream_size,
const std::vector<SubsampleEntry>& subsamples) {
DCHECK(stream);
DCHECK_GT(stream_size, 0);
stream_ = stream;
bytes_left_ = stream_size;
previous_nalu_range_.clear();
encrypted_ranges_.clear();
const uint8_t* start = stream;
const uint8_t* stream_end = stream_ + bytes_left_;
for (size_t i = 0; i < subsamples.size() && start < stream_end; ++i) {
start += subsamples[i].clear_bytes;
const uint8_t* end =
std::min(start + subsamples[i].cypher_bytes, stream_end);
encrypted_ranges_.Add(start, end);
start = end;
}
}
bool H266NaluParser::LocateNALU(off_t* nalu_size, off_t* start_code_size) {
// Find the start code of next NALU.
off_t nalu_start_off = 0;
off_t annexb_start_code_size = 0;
if (!H264Parser::FindStartCodeInClearRanges(
stream_, bytes_left_, encrypted_ranges_, &nalu_start_off,
&annexb_start_code_size)) {
DVLOG(4) << "Could not find start code, end of stream?";
return false;
}
// Move the stream to the beginning of the NALU (pointing at the start code).
stream_ += nalu_start_off;
bytes_left_ -= nalu_start_off;
const uint8_t* nalu_data = stream_ + annexb_start_code_size;
off_t max_nalu_data_size = bytes_left_ - annexb_start_code_size;
if (max_nalu_data_size <= 0) {
DVLOG(3) << "End of stream";
return false;
}
// Find the start code of next NALU;
// if successful, |nalu_size_without_start_code| is the number of bytes from
// after previous start code to before this one;
// if next start code is not found, it is still a valid NALU since there
// are some bytes left after the first start code: all the remaining bytes
// belong to the current NALU.
off_t next_start_code_size = 0;
off_t nalu_size_without_start_code = 0;
if (!H264Parser::FindStartCodeInClearRanges(
nalu_data, max_nalu_data_size, encrypted_ranges_,
&nalu_size_without_start_code, &next_start_code_size)) {
nalu_size_without_start_code = max_nalu_data_size;
}
*nalu_size = nalu_size_without_start_code + annexb_start_code_size;
*start_code_size = annexb_start_code_size;
return true;
}
H266NaluParser::Result H266NaluParser::AdvanceToNextNALU(H266NALU* nalu) {
off_t start_code_size;
off_t nalu_size_with_start_code;
if (!LocateNALU(&nalu_size_with_start_code, &start_code_size)) {
DVLOG(4) << "Could not find next NALU, bytes left in stream: "
<< bytes_left_;
return kEndOfStream;
}
DCHECK(nalu);
nalu->data = stream_ + start_code_size;
nalu->size = nalu_size_with_start_code - start_code_size;
DVLOG(4) << "NALU found: size=" << nalu_size_with_start_code;
// Initialize bit reader at the start of found NALU.
if (!br_.Initialize(nalu->data, nalu->size)) {
return kEndOfStream;
}
// Move parser state to after this NALU, so next time AdvanceToNextNALU
// is called, we will effectively be skipping it;
// other parsing functions will use the position saved
// in bit reader for parsing, so we don't have to remember it here.
stream_ += nalu_size_with_start_code;
bytes_left_ -= nalu_size_with_start_code;
// Read NALU header, skip the forbidden_zero_bit, but check for it.
int data;
READ_BITS_OR_RETURN(1, &data);
TRUE_OR_RETURN(data == 0);
// nuh_reserved_zero_bit
READ_BITS_OR_RETURN(1, &data);
if (data == 1) {
// Current spec requires ignoring NALU with nuh_reserved_zero_bit == 1.
return kIgnored;
}
READ_BITS_OR_RETURN(6, &nalu->nuh_layer_id);
if (nalu->nuh_layer_id < 0 || nalu->nuh_layer_id > 55) {
return kIgnored;
}
READ_BITS_OR_RETURN(5, &nalu->nal_unit_type);
READ_BITS_OR_RETURN(3, &nalu->nuh_temporal_id_plus1);
TRUE_OR_RETURN(nalu->nuh_temporal_id_plus1 != 0);
if (nalu->nal_unit_type >= H266NALU::kIDRWithRADL &&
nalu->nal_unit_type <= H266NALU::kReservedIRAP11) {
TRUE_OR_RETURN(nalu->nuh_temporal_id_plus1 == 1);
}
DVLOG(4) << "NALU type: " << static_cast<int>(nalu->nal_unit_type)
<< " at: " << reinterpret_cast<const void*>(nalu->data)
<< " size: " << nalu->size;
previous_nalu_range_.clear();
previous_nalu_range_.Add(nalu->data, nalu->data + nalu->size);
return kOk;
}
std::vector<SubsampleEntry> H266NaluParser::GetCurrentSubsamples() {
DCHECK_EQ(previous_nalu_range_.size(), 1u)
<< "This should only be called after a "
"successful call to AdvanceToNextNalu()";
auto intersection = encrypted_ranges_.IntersectionWith(previous_nalu_range_);
return EncryptedRangesToSubsampleEntry(
previous_nalu_range_.start(0), previous_nalu_range_.end(0), intersection);
}
} // namespace media
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