webrtc/modules/rtp_rtcp/source/rtp_payload_registry.cc - src - Git at Google

 /*
  *  Copyright (c) 2013 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */

 #include "webrtc/modules/rtp_rtcp/include/rtp_payload_registry.h"

 #include "webrtc/base/logging.h"
 #include "webrtc/modules/rtp_rtcp/source/byte_io.h"

 namespace webrtc {

 RTPPayloadRegistry::RTPPayloadRegistry(RTPPayloadStrategy* rtp_payload_strategy)
     : rtp_payload_strategy_(rtp_payload_strategy),
       red_payload_type_(-1),
       ulpfec_payload_type_(-1),
       incoming_payload_type_(-1),
       last_received_payload_type_(-1),
       last_received_media_payload_type_(-1),
       rtx_(false),
       rtx_payload_type_(-1),
       ssrc_rtx_(0) {}

 RTPPayloadRegistry::~RTPPayloadRegistry() {
   while (!payload_type_map_.empty()) {
     RtpUtility::PayloadTypeMap::iterator it = payload_type_map_.begin();
     delete it->second;
     payload_type_map_.erase(it);
   }
 }

 int32_t RTPPayloadRegistry::RegisterReceivePayload(
     const char payload_name[RTP_PAYLOAD_NAME_SIZE],
     const int8_t payload_type,
     const uint32_t frequency,
     const size_t channels,
     const uint32_t rate,
     bool* created_new_payload) {
   assert(payload_type >= 0);
   assert(payload_name);
   *created_new_payload = false;

   // Sanity check.
   switch (payload_type) {
     // Reserved payload types to avoid RTCP conflicts when marker bit is set.
     case 64:        //  192 Full INTRA-frame request.
     case 72:        //  200 Sender report.
     case 73:        //  201 Receiver report.
     case 74:        //  202 Source description.
     case 75:        //  203 Goodbye.
     case 76:        //  204 Application-defined.
     case 77:        //  205 Transport layer FB message.
     case 78:        //  206 Payload-specific FB message.
     case 79:        //  207 Extended report.
       LOG(LS_ERROR) << "Can't register invalid receiver payload type: "
                     << payload_type;
       return -1;
     default:
       break;
   }

   size_t payload_name_length = strlen(payload_name);

   rtc::CritScope cs(&crit_sect_);

   RtpUtility::PayloadTypeMap::iterator it =
       payload_type_map_.find(payload_type);

   if (it != payload_type_map_.end()) {
     // We already use this payload type.
     RtpUtility::Payload* payload = it->second;

     assert(payload);

     size_t name_length = strlen(payload->name);

     // Check if it's the same as we already have.
     // If same, ignore sending an error.
     if (payload_name_length == name_length &&
         RtpUtility::StringCompare(
             payload->name, payload_name, payload_name_length)) {
       if (rtp_payload_strategy_->PayloadIsCompatible(*payload, frequency,
                                                      channels, rate)) {
         rtp_payload_strategy_->UpdatePayloadRate(payload, rate);
         return 0;
       }
     }
     LOG(LS_ERROR) << "Payload type already registered: "
                   << static_cast<int>(payload_type);
     return -1;
   }

   if (rtp_payload_strategy_->CodecsMustBeUnique()) {
     DeregisterAudioCodecOrRedTypeRegardlessOfPayloadType(
         payload_name, payload_name_length, frequency, channels, rate);
   }

   RtpUtility::Payload* payload = rtp_payload_strategy_->CreatePayloadType(
       payload_name, payload_type, frequency, channels, rate);

   payload_type_map_[payload_type] = payload;
   *created_new_payload = true;

   if (RtpUtility::StringCompare(payload_name, "red", 3)) {
     red_payload_type_ = payload_type;
   } else if (RtpUtility::StringCompare(payload_name, "ulpfec", 6)) {
     ulpfec_payload_type_ = payload_type;
   }

   // Successful set of payload type, clear the value of last received payload
   // type since it might mean something else.
   last_received_payload_type_ = -1;
   last_received_media_payload_type_ = -1;
   return 0;
 }

 int32_t RTPPayloadRegistry::DeRegisterReceivePayload(
     const int8_t payload_type) {
   rtc::CritScope cs(&crit_sect_);
   RtpUtility::PayloadTypeMap::iterator it =
       payload_type_map_.find(payload_type);
   assert(it != payload_type_map_.end());
   delete it->second;
   payload_type_map_.erase(it);
   return 0;
 }

 // There can't be several codecs with the same rate, frequency and channels
 // for audio codecs, but there can for video.
 // Always called from within a critical section.
 void RTPPayloadRegistry::DeregisterAudioCodecOrRedTypeRegardlessOfPayloadType(
     const char payload_name[RTP_PAYLOAD_NAME_SIZE],
     const size_t payload_name_length,
     const uint32_t frequency,
     const size_t channels,
     const uint32_t rate) {
   RtpUtility::PayloadTypeMap::iterator iterator = payload_type_map_.begin();
   for (; iterator != payload_type_map_.end(); ++iterator) {
     RtpUtility::Payload* payload = iterator->second;
     size_t name_length = strlen(payload->name);

     if (payload_name_length == name_length &&
         RtpUtility::StringCompare(
             payload->name, payload_name, payload_name_length)) {
       // We found the payload name in the list.
       // If audio, check frequency and rate.
       if (payload->audio) {
         if (rtp_payload_strategy_->PayloadIsCompatible(*payload, frequency,
                                                        channels, rate)) {
           // Remove old setting.
           delete payload;
           payload_type_map_.erase(iterator);
           break;
         }
       } else if (RtpUtility::StringCompare(payload_name, "red", 3)) {
         delete payload;
         payload_type_map_.erase(iterator);
         break;
       }
     }
   }
 }

 int32_t RTPPayloadRegistry::ReceivePayloadType(
     const char payload_name[RTP_PAYLOAD_NAME_SIZE],
     const uint32_t frequency,
     const size_t channels,
     const uint32_t rate,
     int8_t* payload_type) const {
   assert(payload_type);
   size_t payload_name_length = strlen(payload_name);

   rtc::CritScope cs(&crit_sect_);

   RtpUtility::PayloadTypeMap::const_iterator it = payload_type_map_.begin();

   for (; it != payload_type_map_.end(); ++it) {
     RtpUtility::Payload* payload = it->second;
     assert(payload);

     size_t name_length = strlen(payload->name);
     if (payload_name_length == name_length &&
         RtpUtility::StringCompare(
             payload->name, payload_name, payload_name_length)) {
       // Name matches.
       if (payload->audio) {
         if (rate == 0) {
           // [default] audio, check freq and channels.
           if (payload->typeSpecific.Audio.frequency == frequency &&
               payload->typeSpecific.Audio.channels == channels) {
             *payload_type = it->first;
             return 0;
           }
         } else {
           // Non-default audio, check freq, channels and rate.
           if (payload->typeSpecific.Audio.frequency == frequency &&
               payload->typeSpecific.Audio.channels == channels &&
               payload->typeSpecific.Audio.rate == rate) {
             // extra rate condition added
             *payload_type = it->first;
             return 0;
           }
         }
       } else {
         // Video.
         *payload_type = it->first;
         return 0;
       }
     }
   }
   return -1;
 }

 bool RTPPayloadRegistry::RtxEnabled() const {
   rtc::CritScope cs(&crit_sect_);
   return rtx_;
 }

 bool RTPPayloadRegistry::IsRtx(const RTPHeader& header) const {
   rtc::CritScope cs(&crit_sect_);
   return IsRtxInternal(header);
 }

 bool RTPPayloadRegistry::IsRtxInternal(const RTPHeader& header) const {
   return rtx_ && ssrc_rtx_ == header.ssrc;
 }

 bool RTPPayloadRegistry::RestoreOriginalPacket(uint8_t* restored_packet,
                                                const uint8_t* packet,
                                                size_t* packet_length,
                                                uint32_t original_ssrc,
                                                const RTPHeader& header) const {
   if (kRtxHeaderSize + header.headerLength + header.paddingLength >
       *packet_length) {
     return false;
   }
   const uint8_t* rtx_header = packet + header.headerLength;
   uint16_t original_sequence_number = (rtx_header[0] << 8) + rtx_header[1];

   // Copy the packet into the restored packet, except for the RTX header.
   memcpy(restored_packet, packet, header.headerLength);
   memcpy(restored_packet + header.headerLength,
          packet + header.headerLength + kRtxHeaderSize,
          *packet_length - header.headerLength - kRtxHeaderSize);
   *packet_length -= kRtxHeaderSize;

   // Replace the SSRC and the sequence number with the originals.
   ByteWriter<uint16_t>::WriteBigEndian(restored_packet + 2,
                                        original_sequence_number);
   ByteWriter<uint32_t>::WriteBigEndian(restored_packet + 8, original_ssrc);

   rtc::CritScope cs(&crit_sect_);
   if (!rtx_)
     return true;

   int associated_payload_type;
   auto apt_mapping = rtx_payload_type_map_.find(header.payloadType);
   if (apt_mapping == rtx_payload_type_map_.end())
     return false;
   associated_payload_type = apt_mapping->second;
   if (red_payload_type_ != -1) {
     // Assume red will be used if it's configured.
     // This is a workaround for a Chrome sdp bug where rtx is associated
     // with the media codec even though media is sent over red.
     // TODO(holmer): Remove once the Chrome versions exposing this bug are
     // old enough, which should be once Chrome Stable reaches M53 as this
     // work-around went into M50.
     associated_payload_type = red_payload_type_;
   }
   restored_packet[1] = static_cast<uint8_t>(associated_payload_type);
   if (header.markerBit) {
     restored_packet[1] |= kRtpMarkerBitMask;  // Marker bit is set.
   }
   return true;
 }

 void RTPPayloadRegistry::SetRtxSsrc(uint32_t ssrc) {
   rtc::CritScope cs(&crit_sect_);
   ssrc_rtx_ = ssrc;
   rtx_ = true;
 }

 bool RTPPayloadRegistry::GetRtxSsrc(uint32_t* ssrc) const {
   rtc::CritScope cs(&crit_sect_);
   *ssrc = ssrc_rtx_;
   return rtx_;
 }

 void RTPPayloadRegistry::SetRtxPayloadType(int payload_type,
                                            int associated_payload_type) {
   rtc::CritScope cs(&crit_sect_);
   if (payload_type < 0) {
     LOG(LS_ERROR) << "Invalid RTX payload type: " << payload_type;
     return;
   }

   rtx_payload_type_map_[payload_type] = associated_payload_type;
   rtx_ = true;
   rtx_payload_type_ = payload_type;
 }

 bool RTPPayloadRegistry::IsRed(const RTPHeader& header) const {
   rtc::CritScope cs(&crit_sect_);
   return red_payload_type_ == header.payloadType;
 }

 bool RTPPayloadRegistry::IsEncapsulated(const RTPHeader& header) const {
   return IsRed(header) || IsRtx(header);
 }

 bool RTPPayloadRegistry::GetPayloadSpecifics(uint8_t payload_type,
                                              PayloadUnion* payload) const {
   rtc::CritScope cs(&crit_sect_);
   RtpUtility::PayloadTypeMap::const_iterator it =
       payload_type_map_.find(payload_type);

   // Check that this is a registered payload type.
   if (it == payload_type_map_.end()) {
     return false;
   }
   *payload = it->second->typeSpecific;
   return true;
 }

 int RTPPayloadRegistry::GetPayloadTypeFrequency(
     uint8_t payload_type) const {
   const RtpUtility::Payload* payload = PayloadTypeToPayload(payload_type);
   if (!payload) {
     return -1;
   }
   rtc::CritScope cs(&crit_sect_);
   return rtp_payload_strategy_->GetPayloadTypeFrequency(*payload);
 }

 const RtpUtility::Payload* RTPPayloadRegistry::PayloadTypeToPayload(
     uint8_t payload_type) const {
   rtc::CritScope cs(&crit_sect_);

   RtpUtility::PayloadTypeMap::const_iterator it =
       payload_type_map_.find(payload_type);

   // Check that this is a registered payload type.
   if (it == payload_type_map_.end()) {
     return nullptr;
   }

   return it->second;
 }

 void RTPPayloadRegistry::SetIncomingPayloadType(const RTPHeader& header) {
   rtc::CritScope cs(&crit_sect_);
   if (!IsRtxInternal(header))
     incoming_payload_type_ = header.payloadType;
 }

 bool RTPPayloadRegistry::ReportMediaPayloadType(uint8_t media_payload_type) {
   rtc::CritScope cs(&crit_sect_);
   if (last_received_media_payload_type_ == media_payload_type) {
     // Media type unchanged.
     return true;
   }
   last_received_media_payload_type_ = media_payload_type;
   return false;
 }

 class RTPPayloadAudioStrategy : public RTPPayloadStrategy {
  public:
   bool CodecsMustBeUnique() const override { return true; }

   bool PayloadIsCompatible(const RtpUtility::Payload& payload,
                            const uint32_t frequency,
                            const size_t channels,
                            const uint32_t rate) const override {
     return
         payload.audio &&
         payload.typeSpecific.Audio.frequency == frequency &&
         payload.typeSpecific.Audio.channels == channels &&
         (payload.typeSpecific.Audio.rate == rate ||
             payload.typeSpecific.Audio.rate == 0 || rate == 0);
   }

   void UpdatePayloadRate(RtpUtility::Payload* payload,
                          const uint32_t rate) const override {
     payload->typeSpecific.Audio.rate = rate;
   }

   RtpUtility::Payload* CreatePayloadType(
       const char payloadName[RTP_PAYLOAD_NAME_SIZE],
       const int8_t payloadType,
       const uint32_t frequency,
       const size_t channels,
       const uint32_t rate) const override {
     RtpUtility::Payload* payload = new RtpUtility::Payload;
     payload->name[RTP_PAYLOAD_NAME_SIZE - 1] = 0;
     strncpy(payload->name, payloadName, RTP_PAYLOAD_NAME_SIZE - 1);
     assert(frequency >= 1000);
     payload->typeSpecific.Audio.frequency = frequency;
     payload->typeSpecific.Audio.channels = channels;
     payload->typeSpecific.Audio.rate = rate;
     payload->audio = true;
     return payload;
   }

   int GetPayloadTypeFrequency(
       const RtpUtility::Payload& payload) const override {
     return payload.typeSpecific.Audio.frequency;
   }
 };

 class RTPPayloadVideoStrategy : public RTPPayloadStrategy {
  public:
   bool CodecsMustBeUnique() const override { return false; }

   bool PayloadIsCompatible(const RtpUtility::Payload& payload,
                            const uint32_t frequency,
                            const size_t channels,
                            const uint32_t rate) const override {
     return !payload.audio;
   }

   void UpdatePayloadRate(RtpUtility::Payload* payload,
                          const uint32_t rate) const override {}

   RtpUtility::Payload* CreatePayloadType(
       const char payloadName[RTP_PAYLOAD_NAME_SIZE],
       const int8_t payloadType,
       const uint32_t frequency,
       const size_t channels,
       const uint32_t rate) const override {
     RtpVideoCodecTypes videoType = kRtpVideoGeneric;

     if (RtpUtility::StringCompare(payloadName, "VP8", 3)) {
       videoType = kRtpVideoVp8;
     } else if (RtpUtility::StringCompare(payloadName, "VP9", 3)) {
       videoType = kRtpVideoVp9;
     } else if (RtpUtility::StringCompare(payloadName, "H264", 4)) {
       videoType = kRtpVideoH264;
     } else if (RtpUtility::StringCompare(payloadName, "I420", 4)) {
       videoType = kRtpVideoGeneric;
     } else if (RtpUtility::StringCompare(payloadName, "ULPFEC", 6) ||
         RtpUtility::StringCompare(payloadName, "RED", 3)) {
       videoType = kRtpVideoNone;
     } else {
       videoType = kRtpVideoGeneric;
     }
     RtpUtility::Payload* payload = new RtpUtility::Payload;

     payload->name[RTP_PAYLOAD_NAME_SIZE - 1] = 0;
     strncpy(payload->name, payloadName, RTP_PAYLOAD_NAME_SIZE - 1);
     payload->typeSpecific.Video.videoCodecType = videoType;
     payload->audio = false;
     return payload;
   }

   int GetPayloadTypeFrequency(
       const RtpUtility::Payload& payload) const override {
     return kVideoPayloadTypeFrequency;
   }
 };

 RTPPayloadStrategy* RTPPayloadStrategy::CreateStrategy(
     const bool handling_audio) {
   if (handling_audio) {
     return new RTPPayloadAudioStrategy();
   } else {
     return new RTPPayloadVideoStrategy();
   }
 }

 }  // namespace webrtc
	/*
	* Copyright (c) 2013 The WebRTC project authors. All Rights Reserved.
	*
	* Use of this source code is governed by a BSD-style license
	* that can be found in the LICENSE file in the root of the source
	* tree. An additional intellectual property rights grant can be found
	* in the file PATENTS. All contributing project authors may
	* be found in the AUTHORS file in the root of the source tree.
	*/

	#include "webrtc/modules/rtp_rtcp/include/rtp_payload_registry.h"

	#include "webrtc/base/logging.h"
	#include "webrtc/modules/rtp_rtcp/source/byte_io.h"

	namespace webrtc {

	RTPPayloadRegistry::RTPPayloadRegistry(RTPPayloadStrategy* rtp_payload_strategy)
	: rtp_payload_strategy_(rtp_payload_strategy),
	red_payload_type_(-1),
	ulpfec_payload_type_(-1),
	incoming_payload_type_(-1),
	last_received_payload_type_(-1),
	last_received_media_payload_type_(-1),
	rtx_(false),
	rtx_payload_type_(-1),
	ssrc_rtx_(0) {}

	RTPPayloadRegistry::~RTPPayloadRegistry() {
	while (!payload_type_map_.empty()) {
	RtpUtility::PayloadTypeMap::iterator it = payload_type_map_.begin();
	delete it->second;
	payload_type_map_.erase(it);
	}
	}

	int32_t RTPPayloadRegistry::RegisterReceivePayload(
	const char payload_name[RTP_PAYLOAD_NAME_SIZE],
	const int8_t payload_type,
	const uint32_t frequency,
	const size_t channels,
	const uint32_t rate,
	bool* created_new_payload) {
	assert(payload_type >= 0);
	assert(payload_name);
	*created_new_payload = false;

	// Sanity check.
	switch (payload_type) {
	// Reserved payload types to avoid RTCP conflicts when marker bit is set.
	case 64: // 192 Full INTRA-frame request.
	case 72: // 200 Sender report.
	case 73: // 201 Receiver report.
	case 74: // 202 Source description.
	case 75: // 203 Goodbye.
	case 76: // 204 Application-defined.
	case 77: // 205 Transport layer FB message.
	case 78: // 206 Payload-specific FB message.
	case 79: // 207 Extended report.
	LOG(LS_ERROR) << "Can't register invalid receiver payload type: "
	<< payload_type;
	return -1;
	default:
	break;
	}

	size_t payload_name_length = strlen(payload_name);

	rtc::CritScope cs(&crit_sect_);

	RtpUtility::PayloadTypeMap::iterator it =
	payload_type_map_.find(payload_type);

	if (it != payload_type_map_.end()) {
	// We already use this payload type.
	RtpUtility::Payload* payload = it->second;

	assert(payload);

	size_t name_length = strlen(payload->name);

	// Check if it's the same as we already have.
	// If same, ignore sending an error.
	if (payload_name_length == name_length &&
	RtpUtility::StringCompare(
	payload->name, payload_name, payload_name_length)) {
	if (rtp_payload_strategy_->PayloadIsCompatible(*payload, frequency,
	channels, rate)) {
	rtp_payload_strategy_->UpdatePayloadRate(payload, rate);
	return 0;
	}
	}
	LOG(LS_ERROR) << "Payload type already registered: "
	<< static_cast<int>(payload_type);
	return -1;
	}

	if (rtp_payload_strategy_->CodecsMustBeUnique()) {
	DeregisterAudioCodecOrRedTypeRegardlessOfPayloadType(
	payload_name, payload_name_length, frequency, channels, rate);
	}

	RtpUtility::Payload* payload = rtp_payload_strategy_->CreatePayloadType(
	payload_name, payload_type, frequency, channels, rate);

	payload_type_map_[payload_type] = payload;
	*created_new_payload = true;

	if (RtpUtility::StringCompare(payload_name, "red", 3)) {
	red_payload_type_ = payload_type;
	} else if (RtpUtility::StringCompare(payload_name, "ulpfec", 6)) {
	ulpfec_payload_type_ = payload_type;
	}

	// Successful set of payload type, clear the value of last received payload
	// type since it might mean something else.
	last_received_payload_type_ = -1;
	last_received_media_payload_type_ = -1;
	return 0;
	}

	int32_t RTPPayloadRegistry::DeRegisterReceivePayload(
	const int8_t payload_type) {
	rtc::CritScope cs(&crit_sect_);
	RtpUtility::PayloadTypeMap::iterator it =
	payload_type_map_.find(payload_type);
	assert(it != payload_type_map_.end());
	delete it->second;
	payload_type_map_.erase(it);
	return 0;
	}

	// There can't be several codecs with the same rate, frequency and channels
	// for audio codecs, but there can for video.
	// Always called from within a critical section.
	void RTPPayloadRegistry::DeregisterAudioCodecOrRedTypeRegardlessOfPayloadType(
	const char payload_name[RTP_PAYLOAD_NAME_SIZE],
	const size_t payload_name_length,
	const uint32_t frequency,
	const size_t channels,
	const uint32_t rate) {
	RtpUtility::PayloadTypeMap::iterator iterator = payload_type_map_.begin();
	for (; iterator != payload_type_map_.end(); ++iterator) {
	RtpUtility::Payload* payload = iterator->second;
	size_t name_length = strlen(payload->name);

	if (payload_name_length == name_length &&
	RtpUtility::StringCompare(
	payload->name, payload_name, payload_name_length)) {
	// We found the payload name in the list.
	// If audio, check frequency and rate.
	if (payload->audio) {
	if (rtp_payload_strategy_->PayloadIsCompatible(*payload, frequency,
	channels, rate)) {
	// Remove old setting.
	delete payload;
	payload_type_map_.erase(iterator);
	break;
	}
	} else if (RtpUtility::StringCompare(payload_name, "red", 3)) {
	delete payload;
	payload_type_map_.erase(iterator);
	break;
	}
	}
	}
	}

	int32_t RTPPayloadRegistry::ReceivePayloadType(
	const char payload_name[RTP_PAYLOAD_NAME_SIZE],
	const uint32_t frequency,
	const size_t channels,
	const uint32_t rate,
	int8_t* payload_type) const {
	assert(payload_type);
	size_t payload_name_length = strlen(payload_name);

	rtc::CritScope cs(&crit_sect_);

	RtpUtility::PayloadTypeMap::const_iterator it = payload_type_map_.begin();

	for (; it != payload_type_map_.end(); ++it) {
	RtpUtility::Payload* payload = it->second;
	assert(payload);

	size_t name_length = strlen(payload->name);
	if (payload_name_length == name_length &&
	RtpUtility::StringCompare(
	payload->name, payload_name, payload_name_length)) {
	// Name matches.
	if (payload->audio) {
	if (rate == 0) {
	// [default] audio, check freq and channels.
	if (payload->typeSpecific.Audio.frequency == frequency &&
	payload->typeSpecific.Audio.channels == channels) {
	*payload_type = it->first;
	return 0;
	}
	} else {
	// Non-default audio, check freq, channels and rate.
	if (payload->typeSpecific.Audio.frequency == frequency &&
	payload->typeSpecific.Audio.channels == channels &&
	payload->typeSpecific.Audio.rate == rate) {
	// extra rate condition added
	*payload_type = it->first;
	return 0;
	}
	}
	} else {
	// Video.
	*payload_type = it->first;
	return 0;
	}
	}
	}
	return -1;
	}

	bool RTPPayloadRegistry::RtxEnabled() const {
	rtc::CritScope cs(&crit_sect_);
	return rtx_;
	}

	bool RTPPayloadRegistry::IsRtx(const RTPHeader& header) const {
	rtc::CritScope cs(&crit_sect_);
	return IsRtxInternal(header);
	}

	bool RTPPayloadRegistry::IsRtxInternal(const RTPHeader& header) const {
	return rtx_ && ssrc_rtx_ == header.ssrc;
	}

	bool RTPPayloadRegistry::RestoreOriginalPacket(uint8_t* restored_packet,
	const uint8_t* packet,
	size_t* packet_length,
	uint32_t original_ssrc,
	const RTPHeader& header) const {
	if (kRtxHeaderSize + header.headerLength + header.paddingLength >
	*packet_length) {
	return false;
	}
	const uint8_t* rtx_header = packet + header.headerLength;
	uint16_t original_sequence_number = (rtx_header[0] << 8) + rtx_header[1];

	// Copy the packet into the restored packet, except for the RTX header.
	memcpy(restored_packet, packet, header.headerLength);
	memcpy(restored_packet + header.headerLength,
	packet + header.headerLength + kRtxHeaderSize,
	*packet_length - header.headerLength - kRtxHeaderSize);
	*packet_length -= kRtxHeaderSize;

	// Replace the SSRC and the sequence number with the originals.
	ByteWriter<uint16_t>::WriteBigEndian(restored_packet + 2,
	original_sequence_number);
	ByteWriter<uint32_t>::WriteBigEndian(restored_packet + 8, original_ssrc);

	rtc::CritScope cs(&crit_sect_);
	if (!rtx_)
	return true;

	int associated_payload_type;
	auto apt_mapping = rtx_payload_type_map_.find(header.payloadType);
	if (apt_mapping == rtx_payload_type_map_.end())
	return false;
	associated_payload_type = apt_mapping->second;
	if (red_payload_type_ != -1) {
	// Assume red will be used if it's configured.
	// This is a workaround for a Chrome sdp bug where rtx is associated
	// with the media codec even though media is sent over red.
	// TODO(holmer): Remove once the Chrome versions exposing this bug are
	// old enough, which should be once Chrome Stable reaches M53 as this
	// work-around went into M50.
	associated_payload_type = red_payload_type_;
	}
	restored_packet[1] = static_cast<uint8_t>(associated_payload_type);
	if (header.markerBit) {
	restored_packet[1] \|= kRtpMarkerBitMask; // Marker bit is set.
	}
	return true;
	}

	void RTPPayloadRegistry::SetRtxSsrc(uint32_t ssrc) {
	rtc::CritScope cs(&crit_sect_);
	ssrc_rtx_ = ssrc;
	rtx_ = true;
	}

	bool RTPPayloadRegistry::GetRtxSsrc(uint32_t* ssrc) const {
	rtc::CritScope cs(&crit_sect_);
	*ssrc = ssrc_rtx_;
	return rtx_;
	}

	void RTPPayloadRegistry::SetRtxPayloadType(int payload_type,
	int associated_payload_type) {
	rtc::CritScope cs(&crit_sect_);
	if (payload_type < 0) {
	LOG(LS_ERROR) << "Invalid RTX payload type: " << payload_type;
	return;
	}

	rtx_payload_type_map_[payload_type] = associated_payload_type;
	rtx_ = true;
	rtx_payload_type_ = payload_type;
	}

	bool RTPPayloadRegistry::IsRed(const RTPHeader& header) const {
	rtc::CritScope cs(&crit_sect_);
	return red_payload_type_ == header.payloadType;
	}

	bool RTPPayloadRegistry::IsEncapsulated(const RTPHeader& header) const {
	return IsRed(header) \|\| IsRtx(header);
	}

	bool RTPPayloadRegistry::GetPayloadSpecifics(uint8_t payload_type,
	PayloadUnion* payload) const {
	rtc::CritScope cs(&crit_sect_);
	RtpUtility::PayloadTypeMap::const_iterator it =
	payload_type_map_.find(payload_type);

	// Check that this is a registered payload type.
	if (it == payload_type_map_.end()) {
	return false;
	}
	*payload = it->second->typeSpecific;
	return true;
	}

	int RTPPayloadRegistry::GetPayloadTypeFrequency(
	uint8_t payload_type) const {
	const RtpUtility::Payload* payload = PayloadTypeToPayload(payload_type);
	if (!payload) {
	return -1;
	}
	rtc::CritScope cs(&crit_sect_);
	return rtp_payload_strategy_->GetPayloadTypeFrequency(*payload);
	}

	const RtpUtility::Payload* RTPPayloadRegistry::PayloadTypeToPayload(
	uint8_t payload_type) const {
	rtc::CritScope cs(&crit_sect_);

	RtpUtility::PayloadTypeMap::const_iterator it =
	payload_type_map_.find(payload_type);

	// Check that this is a registered payload type.
	if (it == payload_type_map_.end()) {
	return nullptr;
	}

	return it->second;
	}

	void RTPPayloadRegistry::SetIncomingPayloadType(const RTPHeader& header) {
	rtc::CritScope cs(&crit_sect_);
	if (!IsRtxInternal(header))
	incoming_payload_type_ = header.payloadType;
	}

	bool RTPPayloadRegistry::ReportMediaPayloadType(uint8_t media_payload_type) {
	rtc::CritScope cs(&crit_sect_);
	if (last_received_media_payload_type_ == media_payload_type) {
	// Media type unchanged.
	return true;
	}
	last_received_media_payload_type_ = media_payload_type;
	return false;
	}

	class RTPPayloadAudioStrategy : public RTPPayloadStrategy {
	public:
	bool CodecsMustBeUnique() const override { return true; }

	bool PayloadIsCompatible(const RtpUtility::Payload& payload,
	const uint32_t frequency,
	const size_t channels,
	const uint32_t rate) const override {
	return
	payload.audio &&
	payload.typeSpecific.Audio.frequency == frequency &&
	payload.typeSpecific.Audio.channels == channels &&
	(payload.typeSpecific.Audio.rate == rate \|\|
	payload.typeSpecific.Audio.rate == 0 \|\| rate == 0);
	}

	void UpdatePayloadRate(RtpUtility::Payload* payload,
	const uint32_t rate) const override {
	payload->typeSpecific.Audio.rate = rate;
	}

	RtpUtility::Payload* CreatePayloadType(
	const char payloadName[RTP_PAYLOAD_NAME_SIZE],
	const int8_t payloadType,
	const uint32_t frequency,
	const size_t channels,
	const uint32_t rate) const override {
	RtpUtility::Payload* payload = new RtpUtility::Payload;
	payload->name[RTP_PAYLOAD_NAME_SIZE - 1] = 0;
	strncpy(payload->name, payloadName, RTP_PAYLOAD_NAME_SIZE - 1);
	assert(frequency >= 1000);
	payload->typeSpecific.Audio.frequency = frequency;
	payload->typeSpecific.Audio.channels = channels;
	payload->typeSpecific.Audio.rate = rate;
	payload->audio = true;
	return payload;
	}

	int GetPayloadTypeFrequency(
	const RtpUtility::Payload& payload) const override {
	return payload.typeSpecific.Audio.frequency;
	}
	};

	class RTPPayloadVideoStrategy : public RTPPayloadStrategy {
	public:
	bool CodecsMustBeUnique() const override { return false; }

	bool PayloadIsCompatible(const RtpUtility::Payload& payload,
	const uint32_t frequency,
	const size_t channels,
	const uint32_t rate) const override {
	return !payload.audio;
	}

	void UpdatePayloadRate(RtpUtility::Payload* payload,
	const uint32_t rate) const override {}

	RtpUtility::Payload* CreatePayloadType(
	const char payloadName[RTP_PAYLOAD_NAME_SIZE],
	const int8_t payloadType,
	const uint32_t frequency,
	const size_t channels,
	const uint32_t rate) const override {
	RtpVideoCodecTypes videoType = kRtpVideoGeneric;

	if (RtpUtility::StringCompare(payloadName, "VP8", 3)) {
	videoType = kRtpVideoVp8;
	} else if (RtpUtility::StringCompare(payloadName, "VP9", 3)) {
	videoType = kRtpVideoVp9;
	} else if (RtpUtility::StringCompare(payloadName, "H264", 4)) {
	videoType = kRtpVideoH264;
	} else if (RtpUtility::StringCompare(payloadName, "I420", 4)) {
	videoType = kRtpVideoGeneric;
	} else if (RtpUtility::StringCompare(payloadName, "ULPFEC", 6) \|\|
	RtpUtility::StringCompare(payloadName, "RED", 3)) {
	videoType = kRtpVideoNone;
	} else {
	videoType = kRtpVideoGeneric;
	}
	RtpUtility::Payload* payload = new RtpUtility::Payload;

	payload->name[RTP_PAYLOAD_NAME_SIZE - 1] = 0;
	strncpy(payload->name, payloadName, RTP_PAYLOAD_NAME_SIZE - 1);
	payload->typeSpecific.Video.videoCodecType = videoType;
	payload->audio = false;
	return payload;
	}

	int GetPayloadTypeFrequency(
	const RtpUtility::Payload& payload) const override {
	return kVideoPayloadTypeFrequency;
	}
	};

	RTPPayloadStrategy* RTPPayloadStrategy::CreateStrategy(
	const bool handling_audio) {
	if (handling_audio) {
	return new RTPPayloadAudioStrategy();
	} else {
	return new RTPPayloadVideoStrategy();
	}
	}

	} // namespace webrtc