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H264RtpDepacketizer: De-packetize access units rather than individual NALUs #1135

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Apr 25, 2024
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H264RtpDepacketizer: De-packetize access units rather than individual NALUs #1135

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7 changes: 6 additions & 1 deletion include/rtc/h264rtpdepacketizer.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -15,6 +15,7 @@
#include "common.hpp"
#include "mediahandler.hpp"
#include "message.hpp"
#include "nalunit.hpp"
#include "rtp.hpp"

#include <iterator>
Expand All @@ -24,14 +25,18 @@ namespace rtc {
/// RTP depacketization for H264
class RTC_CPP_EXPORT H264RtpDepacketizer : public MediaHandler {
public:
H264RtpDepacketizer() = default;
using Separator = NalUnit::Separator;

H264RtpDepacketizer(Separator separator = Separator::LongStartSequence);
virtual ~H264RtpDepacketizer() = default;

void incoming(message_vector &messages, const message_callback &send) override;

private:
std::vector<message_ptr> mRtpBuffer;
const NalUnit::Separator mSeparator;

void addSeparator(binary &accessUnit);
message_vector buildFrames(message_vector::iterator firstPkt, message_vector::iterator lastPkt,
uint8_t payloadType, uint32_t timestamp);
};
Expand Down
112 changes: 61 additions & 51 deletions src/h264rtpdepacketizer.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -10,96 +10,105 @@

#include "h264rtpdepacketizer.hpp"
#include "nalunit.hpp"
#include "track.hpp"

#include "impl/logcounter.hpp"

#include <cmath>
#include <utility>

#ifdef _WIN32
#include <winsock2.h>
#else
#include <arpa/inet.h>
#endif
#include "impl/internals.hpp"

namespace rtc {

const unsigned long stapaHeaderSize = 1;
const auto fuaHeaderSize = 2;
const binary naluLongStartCode = {byte{0}, byte{0}, byte{0}, byte{1}};
const binary naluShortStartCode = {byte{0}, byte{0}, byte{1}};

const uint8_t naluTypeSTAPA = 24;
const uint8_t naluTypeFUA = 28;

H264RtpDepacketizer::H264RtpDepacketizer(Separator separator) : mSeparator(separator) {
if (separator != Separator::StartSequence && separator != Separator::LongStartSequence &&
separator != Separator::ShortStartSequence) {
throw std::invalid_argument("Invalid separator");
}
}

void H264RtpDepacketizer::addSeparator(binary &accessUnit) {
if (mSeparator == Separator::StartSequence || mSeparator == Separator::LongStartSequence) {
accessUnit.insert(accessUnit.end(), naluLongStartCode.begin(), naluLongStartCode.end());
} else if (mSeparator == Separator::ShortStartSequence) {
accessUnit.insert(accessUnit.end(), naluShortStartCode.begin(), naluShortStartCode.end());
} else {
throw std::invalid_argument("Invalid separator");
}
}

message_vector H264RtpDepacketizer::buildFrames(message_vector::iterator begin,
message_vector::iterator end, uint8_t payloadType, uint32_t timestamp) {
message_vector::iterator end, uint8_t payloadType,
uint32_t timestamp) {
message_vector out = {};
auto fua_buffer = std::vector<std::byte>{};
auto accessUnit = binary{};
auto frameInfo = std::make_shared<FrameInfo>(payloadType, timestamp);
auto nFrags = 0;

for (auto it = begin; it != end; it++) {
for (auto it = begin; it != end; ++it) {
auto pkt = it->get();
auto pktParsed = reinterpret_cast<const rtc::RtpHeader *>(pkt->data());
auto headerSize =
sizeof(rtc::RtpHeader) + pktParsed->csrcCount() + pktParsed->getExtensionHeaderSize();
auto paddingSize = 0;
auto rtpHeaderSize = pktParsed->getSize() + pktParsed->getExtensionHeaderSize();
auto rtpPaddingSize = 0;

if (pktParsed->padding()) {
paddingSize = std::to_integer<uint8_t>(pkt->at(pkt->size() - 1));
rtpPaddingSize = std::to_integer<uint8_t>(pkt->at(pkt->size() - 1));
}

if (pkt->size() == headerSize + paddingSize) {
if (pkt->size() == rtpHeaderSize + rtpPaddingSize) {
PLOG_VERBOSE << "H.264 RTP packet has empty payload";
continue;
}

auto nalUnitHeader = NalUnitHeader{std::to_integer<uint8_t>(pkt->at(headerSize))};
auto nalUnitHeader = NalUnitHeader{std::to_integer<uint8_t>(pkt->at(rtpHeaderSize))};

if (fua_buffer.size() != 0 || nalUnitHeader.unitType() == naluTypeFUA) {
if (fua_buffer.size() == 0) {
fua_buffer.push_back(std::byte(0));
}

auto nalUnitFragmentHeader =
NalUnitFragmentHeader{std::to_integer<uint8_t>(pkt->at(headerSize + 1))};

std::copy(pkt->begin() + headerSize + fuaHeaderSize, pkt->end(),
std::back_inserter(fua_buffer));

if (nalUnitFragmentHeader.isEnd()) {
fua_buffer.at(0) =
std::byte(nalUnitHeader.idc() | nalUnitFragmentHeader.unitType());
if (nalUnitHeader.unitType() == naluTypeFUA) {
auto nalUnitFragmentHeader = NalUnitFragmentHeader{
std::to_integer<uint8_t>(pkt->at(rtpHeaderSize + sizeof(NalUnitHeader)))};

out.push_back(
make_message(std::move(fua_buffer), Message::Binary, 0, nullptr, frameInfo));
fua_buffer.clear();
if (nFrags++ == 0) {
addSeparator(accessUnit);
accessUnit.emplace_back(
byte(nalUnitHeader.idc() | nalUnitFragmentHeader.unitType()));
}

accessUnit.insert(accessUnit.end(),
pkt->begin() + rtpHeaderSize + sizeof(NalUnitHeader) +
sizeof(NalUnitFragmentHeader),
pkt->end());
} else if (nalUnitHeader.unitType() > 0 && nalUnitHeader.unitType() < 24) {
out.push_back(make_message(pkt->begin() + headerSize, pkt->end(), Message::Binary, 0,
nullptr, frameInfo));
addSeparator(accessUnit);
accessUnit.insert(accessUnit.end(), pkt->begin() + rtpHeaderSize, pkt->end());
} else if (nalUnitHeader.unitType() == naluTypeSTAPA) {
auto currOffset = stapaHeaderSize + headerSize;
auto currOffset = rtpHeaderSize + sizeof(NalUnitHeader);

while (currOffset < pkt->size()) {
auto naluSize =
uint16_t(pkt->at(currOffset)) << 8 | uint8_t(pkt->at(currOffset + 1));
while (currOffset + sizeof(uint16_t) < pkt->size()) {
auto naluSize = std::to_integer<uint16_t>(pkt->at(currOffset)) << 8 |
std::to_integer<uint16_t>(pkt->at(currOffset + 1));

currOffset += 2;
currOffset += sizeof(uint16_t);

if (pkt->size() < currOffset + naluSize) {
throw std::runtime_error("STAP-A declared size is larger then buffer");
throw std::runtime_error("H264 STAP-A declared size is larger than buffer");
}

out.push_back(make_message(pkt->begin() + currOffset,
pkt->begin() + currOffset + naluSize, Message::Binary, 0,
nullptr, frameInfo));
addSeparator(accessUnit);
accessUnit.insert(accessUnit.end(), pkt->begin() + currOffset,
pkt->begin() + currOffset + naluSize);

currOffset += naluSize;
}
} else {
throw std::runtime_error("Unknown H264 RTP Packetization");
}
}

if (!accessUnit.empty()) {
out.emplace_back(make_message(accessUnit.begin(), accessUnit.end(), Message::Binary, 0,
nullptr, frameInfo));
}

return out;
}

Expand Down Expand Up @@ -131,7 +140,8 @@ void H264RtpDepacketizer::incoming(message_vector &messages, const message_callb

if (current_timestamp == 0) {
current_timestamp = p->timestamp();
payload_type = p->payloadType(); // should all be the same for data of the same codec
payload_type =
p->payloadType(); // should all be the same for data of the same codec
} else if (current_timestamp != p->timestamp()) {
break;
}
Expand Down
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