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shaka-packager/packager/media/codecs/nalu_reader.cc

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// Copyright 2016 Google LLC. All rights reserved.
//
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file or at
// https://developers.google.com/open-source/licenses/bsd
#include <packager/media/codecs/nalu_reader.h>
#include <iostream>
#include <glog/logging.h>
#include <packager/media/base/buffer_reader.h>
#include <packager/media/codecs/h264_parser.h>
namespace shaka {
namespace media {
namespace {
inline bool IsStartCode(const uint8_t* data) {
return data[0] == 0x00 && data[1] == 0x00 && data[2] == 0x01;
}
// Edits |subsamples| given the number of consumed bytes.
void UpdateSubsamples(uint64_t consumed_bytes,
std::vector<SubsampleEntry>* subsamples) {
if (consumed_bytes == 0 || subsamples->empty()) {
return;
}
size_t num_entries_to_delete = 0;
for (SubsampleEntry& subsample : *subsamples) {
if (subsample.clear_bytes > consumed_bytes) {
subsample.clear_bytes -= consumed_bytes;
consumed_bytes = 0;
break;
}
consumed_bytes -= subsample.clear_bytes;
subsample.clear_bytes = 0;
if (subsample.cipher_bytes > consumed_bytes) {
subsample.cipher_bytes -= consumed_bytes;
consumed_bytes = 0;
break;
}
consumed_bytes -= subsample.cipher_bytes;
subsample.cipher_bytes = 0;
++num_entries_to_delete;
}
subsamples->erase(subsamples->begin(),
subsamples->begin() + num_entries_to_delete);
}
bool IsNaluLengthEncrypted(
uint8_t nalu_length_size,
const std::vector<SubsampleEntry>& subsamples) {
if (subsamples.empty())
return false;
for (const SubsampleEntry& subsample : subsamples) {
if (subsample.clear_bytes >= nalu_length_size) {
return false;
}
nalu_length_size -= subsample.clear_bytes;
if (subsample.cipher_bytes > 0) {
return true;
}
}
// Ran out of subsamples. Assume the rest is in the clear.
return false;
}
} // namespace
Nalu::Nalu() = default;
bool Nalu::Initialize(CodecType type,
const uint8_t* data,
uint64_t size) {
if (type == Nalu::kH264) {
return InitializeFromH264(data, size);
} else {
DCHECK_EQ(Nalu::kH265, type);
return InitializeFromH265(data, size);
}
}
// ITU-T H.264 (02/2014) 7.4.1 NAL unit semantics
bool Nalu::InitializeFromH264(const uint8_t* data, uint64_t size) {
DCHECK(data);
if (size == 0)
return false;
const uint8_t header = data[0];
if ((header & 0x80) != 0) {
LOG(WARNING) << "forbidden_zero_bit shall be equal to 0 (header 0x"
<< std::hex << static_cast<int>(header) << ").";
return false;
}
data_ = data;
header_size_ = 1;
payload_size_ = size - header_size_;
ref_idc_ = (header >> 5) & 0x3;
type_ = header & 0x1F;
// Reserved NAL units are not treated as valid NAL units here.
if (type_ == Nalu::H264_Unspecified || type_ == Nalu::H264_Reserved17 ||
type_ == Nalu::H264_Reserved18 || type_ >= Nalu::H264_Reserved22) {
VLOG(1) << "Unspecified or reserved nal_unit_type " << type_
<< " (header 0x" << std::hex << static_cast<int>(header) << ").";
// Allow reserved NAL units. Some encoders and extended codecs use the
// reserved NAL units to carry their private data.
} else if (type_ == Nalu::H264_IDRSlice || type_ == Nalu::H264_SPS ||
type_ == Nalu::H264_SPSExtension ||
type_ == Nalu::H264_SubsetSPS || type_ == Nalu::H264_PPS) {
if (ref_idc_ == 0) {
LOG(WARNING) << "nal_ref_idc shall not be equal to 0 for nalu type "
<< type_ << " (header 0x" << std::hex
<< static_cast<int>(header) << ").";
return false;
}
} else if (type_ == Nalu::H264_SEIMessage ||
(type_ >= Nalu::H264_AUD && type_ <= Nalu::H264_FillerData)) {
if (ref_idc_ != 0) {
LOG(WARNING) << "nal_ref_idc shall be equal to 0 for nalu type " << type_
<< " (header 0x" << std::hex << static_cast<int>(header)
<< ").";
return false;
}
}
is_aud_ = type_ == H264_AUD;
is_vcl_ = (type_ >= Nalu::H264_NonIDRSlice && type_ <= Nalu::H264_IDRSlice);
is_video_slice_ =
(type_ == Nalu::H264_NonIDRSlice || type_ == Nalu::H264_IDRSlice);
can_start_access_unit_ =
(is_vcl_ || type_ == Nalu::H264_AUD || type_ == Nalu::H264_SPS ||
type_ == Nalu::H264_PPS || type_ == Nalu::H264_SEIMessage ||
(type_ >= Nalu::H264_PrefixNALUnit && type_ <= Nalu::H264_Reserved18));
return true;
}
// ITU-T H.265 (04/2015) 7.4.2.2 NAL unit header semantics
bool Nalu::InitializeFromH265(const uint8_t* data, uint64_t size) {
DCHECK(data);
if (size < 2)
return false;
const uint16_t header = (data[0] << 8) | data[1];
if ((header & 0x8000) != 0) {
LOG(WARNING) << "forbidden_zero_bit shall be equal to 0 (header 0x"
<< std::hex << header << ").";
return false;
}
data_ = data;
header_size_ = 2;
payload_size_ = size - header_size_;
type_ = (header >> 9) & 0x3F;
nuh_layer_id_ = (header >> 3) & 0x3F;
const int nuh_temporal_id_plus1 = header & 0x7;
if (nuh_temporal_id_plus1 == 0) {
LOG(WARNING) << "nul_temporal_id_plus1 shall not be equal to 0 (header 0x"
<< std::hex << header << ").";
return false;
}
nuh_temporal_id_ = nuh_temporal_id_plus1 - 1;
if (type_ == Nalu::H265_EOB && nuh_layer_id_ != 0) {
LOG(WARNING) << "nuh_layer_id shall be equal to 0 for nalu type " << type_
<< " (header 0x" << std::hex << header << ").";
return false;
}
// Reserved NAL units are not treated as valid NAL units here.
if ((type_ >= Nalu::H265_RSV_VCL_N10 && type_ <= Nalu::H265_RSV_VCL_R15) ||
(type_ >= Nalu::H265_RSV_IRAP_VCL22 && type_ < Nalu::H265_RSV_VCL31) ||
(type_ >= Nalu::H265_RSV_NVCL41)) {
VLOG(1) << "Unspecified or reserved nal_unit_type " << type_
<< " (header 0x" << std::hex << header << ").";
// Allow reserved NAL units. Some encoders and extended codecs use the
// reserved NAL units to carry their private data. For example, Dolby Vision
// uses NAL unit type 62.
} else if ((type_ >= Nalu::H265_BLA_W_LP &&
type_ <= Nalu::H265_RSV_IRAP_VCL23) ||
type_ == Nalu::H265_VPS || type_ == Nalu::H265_SPS ||
type_ == Nalu::H265_EOS || type_ == Nalu::H265_EOB) {
if (nuh_temporal_id_ != 0) {
LOG(WARNING) << "TemporalId shall be equal to 0 for nalu type " << type_
<< " (header 0x" << std::hex << header << ").";
return false;
}
} else if (type_ == Nalu::H265_TSA_N || type_ == Nalu::H265_TSA_R ||
(nuh_layer_id_ == 0 &&
(type_ == Nalu::H265_STSA_N || type_ == Nalu::H265_STSA_R))) {
if (nuh_temporal_id_ == 0) {
LOG(WARNING) << "TemporalId shall not be equal to 0 for nalu type "
<< type_ << " (header 0x" << std::hex << header << ").";
return false;
}
}
is_aud_ = type_ == H265_AUD;
is_vcl_ = type_ >= Nalu::H265_TRAIL_N && type_ <= Nalu::H265_RSV_VCL31;
is_video_slice_ = is_vcl_;
can_start_access_unit_ =
nuh_layer_id_ == 0 &&
(is_vcl_ || type_ == Nalu::H265_AUD || type_ == Nalu::H265_VPS ||
type_ == Nalu::H265_SPS || type_ == Nalu::H265_PPS ||
type_ == Nalu::H265_PREFIX_SEI ||
(type_ >= Nalu::H265_RSV_NVCL41 && type_ <= Nalu::H265_RSV_NVCL44) ||
(type_ >= Nalu::H265_UNSPEC48 && type_ <= Nalu::H265_UNSPEC55));
return true;
}
NaluReader::NaluReader(Nalu::CodecType type,
uint8_t nal_length_size,
const uint8_t* stream,
uint64_t stream_size)
: NaluReader(type,
nal_length_size,
stream,
stream_size,
std::vector<SubsampleEntry>()) {}
NaluReader::NaluReader(Nalu::CodecType type,
uint8_t nal_length_size,
const uint8_t* stream,
uint64_t stream_size,
const std::vector<SubsampleEntry>& subsamples)
: stream_(stream),
stream_size_(stream_size),
nalu_type_(type),
nalu_length_size_(nal_length_size),
format_(nal_length_size == 0 ? kAnnexbByteStreamFormat
: kNalUnitStreamFormat),
subsamples_(subsamples) {
DCHECK(stream);
}
NaluReader::~NaluReader() {}
NaluReader::Result NaluReader::Advance(Nalu* nalu) {
if (stream_size_ <= 0)
return NaluReader::kEOStream;
uint8_t nalu_length_size_or_start_code_size;
uint64_t nalu_length;
if (format_ == kAnnexbByteStreamFormat) {
// This will move |stream_| to the start code.
uint64_t nalu_length_with_header;
if (!LocateNaluByStartCode(&nalu_length_with_header,
&nalu_length_size_or_start_code_size)) {
LOG(ERROR) << "Could not find next NALU, bytes left in stream: "
<< stream_size_;
// This is actually an error. Since we always move to past the end of
// each NALU, if there is no next start code, then this is the first call
// and there are no start codes in the stream.
return NaluReader::kInvalidStream;
}
nalu_length = nalu_length_with_header - nalu_length_size_or_start_code_size;
} else {
BufferReader reader(stream_, stream_size_);
if (IsNaluLengthEncrypted(nalu_length_size_, subsamples_)) {
LOG(ERROR) << "NALU length is encrypted.";
return NaluReader::kInvalidStream;
}
if (!reader.ReadNBytesInto8(&nalu_length, nalu_length_size_))
return NaluReader::kInvalidStream;
nalu_length_size_or_start_code_size = nalu_length_size_;
if (nalu_length + nalu_length_size_ > stream_size_) {
LOG(ERROR) << "NALU length exceeds stream size: "
<< stream_size_ << " < " << nalu_length;
return NaluReader::kInvalidStream;
}
if (nalu_length == 0) {
LOG(ERROR) << "NALU size 0";
return NaluReader::kInvalidStream;
}
}
const uint8_t* nalu_data = stream_ + nalu_length_size_or_start_code_size;
if (!nalu->Initialize(nalu_type_, nalu_data, nalu_length))
return NaluReader::kInvalidStream;
// Move parser state to after this NALU, so next time Advance
// is called, we will effectively be skipping it.
stream_ += nalu_length_size_or_start_code_size + nalu_length;
stream_size_ -= nalu_length_size_or_start_code_size + nalu_length;
UpdateSubsamples(nalu_length_size_or_start_code_size + nalu_length,
&subsamples_);
DVLOG(4) << "NALU type: " << static_cast<int>(nalu->type())
<< " at: " << reinterpret_cast<const void*>(nalu->data())
<< " data size: " << nalu->payload_size();
return NaluReader::kOk;
}
bool NaluReader::StartsWithStartCode() {
if (stream_size_ >= 3) {
if (IsStartCode(stream_))
return true;
}
if (stream_size_ >= 4) {
if (stream_[0] == 0x00 && IsStartCode(stream_ + 1))
return true;
}
return false;
}
// static
bool NaluReader::FindStartCode(const uint8_t* data,
uint64_t data_size,
uint64_t* offset,
uint8_t* start_code_size) {
uint64_t bytes_left = data_size;
while (bytes_left >= 3) {
if (IsStartCode(data)) {
// Found three-byte start code, set pointer at its beginning.
*offset = data_size - bytes_left;
*start_code_size = 3;
// If there is a zero byte before this start code,
// then it's actually a four-byte start code, so backtrack one byte.
if (*offset > 0 && *(data - 1) == 0x00) {
--(*offset);
++(*start_code_size);
}
return true;
}
++data;
--bytes_left;
}
// End of data: offset is pointing to the first byte that was not considered
// as a possible start of a start code.
*offset = data_size - bytes_left;
*start_code_size = 0;
return false;
}
// static
bool NaluReader::FindStartCodeInClearRange(
const uint8_t* data,
uint64_t data_size,
uint64_t* offset,
uint8_t* start_code_size,
const std::vector<SubsampleEntry>& subsamples) {
if (subsamples.empty()) {
return FindStartCode(data, data_size, offset, start_code_size);
}
uint64_t current_offset = 0;
for (const SubsampleEntry& subsample : subsamples) {
uint16_t clear_bytes = subsample.clear_bytes;
if (current_offset + clear_bytes > data_size) {
LOG(WARNING) << "The sum of subsample sizes is greater than data_size.";
clear_bytes = data_size - current_offset;
}
// Note that calling FindStartCode() here should get the correct
// start_code_size, even tho data + current_offset may be in the middle of
// the buffer because data + current_offset - 1 is either it shouldn't be
// accessed because it's data - 1 or it is encrypted.
const bool found_start_code = FindStartCode(
data + current_offset, clear_bytes, offset, start_code_size);
if (found_start_code) {
*offset += current_offset;
return true;
}
const uint64_t subsample_size =
subsample.clear_bytes + subsample.cipher_bytes;
current_offset += subsample_size;
if (current_offset > data_size) {
// Assign data_size here so that the returned offset points to the end of
// the data.
current_offset = data_size;
LOG(WARNING) << "The sum of subsamples is greater than data_size.";
break;
}
}
// If there is more that's not specified by the subsample entries, assume it
// is in the clear.
if (current_offset < data_size) {
const bool found_start_code =
FindStartCode(data + current_offset, data_size - current_offset, offset,
start_code_size);
*offset += current_offset;
return found_start_code;
}
// End of data: offset is pointing to the first byte that was not considered
// as a possible start of a start code.
*offset = current_offset;
*start_code_size = 0;
return false;
}
bool NaluReader::LocateNaluByStartCode(uint64_t* nalu_size,
uint8_t* start_code_size) {
// Find the start code of next NALU.
uint64_t nalu_start_off = 0;
uint8_t annexb_start_code_size = 0;
if (!FindStartCodeInClearRange(
stream_, stream_size_,
&nalu_start_off, &annexb_start_code_size, subsamples_)) {
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;
stream_size_ -= nalu_start_off;
// Shift the subsamples so that next call to FindStartCode() takes the updated
// subsample info.
UpdateSubsamples(nalu_start_off, &subsamples_);
const uint8_t* nalu_data = stream_ + annexb_start_code_size;
// This is a temporary subsample entries for finding next nalu. subsamples_
// should not be updated below.
std::vector<SubsampleEntry> subsamples_for_finding_next_nalu;
if (!subsamples_.empty()) {
subsamples_for_finding_next_nalu = subsamples_;
UpdateSubsamples(annexb_start_code_size, &subsamples_for_finding_next_nalu);
}
uint64_t max_nalu_data_size = stream_size_ - 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.
uint64_t nalu_size_without_start_code = 0;
uint8_t next_start_code_size = 0;
while (true) {
if (!FindStartCodeInClearRange(
nalu_data, max_nalu_data_size,
&nalu_size_without_start_code, &next_start_code_size,
subsamples_for_finding_next_nalu)) {
nalu_data += max_nalu_data_size;
break;
}
nalu_data += nalu_size_without_start_code + next_start_code_size;
max_nalu_data_size -= nalu_size_without_start_code + next_start_code_size;
UpdateSubsamples(nalu_size_without_start_code + next_start_code_size,
&subsamples_for_finding_next_nalu);
// If it is not a valid NAL unit, we will continue searching. This is to
// handle the case where emulation prevention are not applied.
Nalu nalu;
if (nalu.Initialize(nalu_type_, nalu_data, max_nalu_data_size)) {
nalu_data -= next_start_code_size;
break;
}
LOG(WARNING) << "Seeing invalid NAL unit. Emulation prevention may not "
"have been applied properly. Assuming it is part of the "
"previous NAL unit.";
}
*nalu_size = nalu_data - stream_;
*start_code_size = annexb_start_code_size;
return true;
}
} // namespace media
} // namespace shaka
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