pc/rtp_transceiver.cc - src - Git at Google

 /*
  *  Copyright 2017 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 "pc/rtp_transceiver.h"

 #include <string>
 #include <utility>

 #include "absl/algorithm/container.h"
 #include "api/rtp_parameters.h"
 #include "pc/channel_manager.h"
 #include "pc/rtp_media_utils.h"
 #include "pc/rtp_parameters_conversion.h"
 #include "rtc_base/checks.h"
 #include "rtc_base/logging.h"

 namespace webrtc {
 namespace {
 template <class T>
 RTCError VerifyCodecPreferences(const std::vector<RtpCodecCapability>& codecs,
                                 const std::vector<T>& send_codecs,
                                 const std::vector<T>& recv_codecs) {
   // If the intersection between codecs and
   // RTCRtpSender.getCapabilities(kind).codecs or the intersection between
   // codecs and RTCRtpReceiver.getCapabilities(kind).codecs only contains RTX,
   // RED or FEC codecs or is an empty set, throw InvalidModificationError.
   // This ensures that we always have something to offer, regardless of
   // transceiver.direction.

   if (!absl::c_any_of(codecs, [&recv_codecs](const RtpCodecCapability& codec) {
         return codec.name != cricket::kRtxCodecName &&
                codec.name != cricket::kRedCodecName &&
                codec.name != cricket::kFlexfecCodecName &&
                absl::c_any_of(recv_codecs, [&codec](const T& recv_codec) {
                  return recv_codec.MatchesCapability(codec);
                });
       })) {
     return RTCError(RTCErrorType::INVALID_MODIFICATION,
                     "Invalid codec preferences: Missing codec from recv "
                     "codec capabilities.");
   }

   if (!absl::c_any_of(codecs, [&send_codecs](const RtpCodecCapability& codec) {
         return codec.name != cricket::kRtxCodecName &&
                codec.name != cricket::kRedCodecName &&
                codec.name != cricket::kFlexfecCodecName &&
                absl::c_any_of(send_codecs, [&codec](const T& send_codec) {
                  return send_codec.MatchesCapability(codec);
                });
       })) {
     return RTCError(RTCErrorType::INVALID_MODIFICATION,
                     "Invalid codec preferences: Missing codec from send "
                     "codec capabilities.");
   }

   // Let codecCapabilities be the union of
   // RTCRtpSender.getCapabilities(kind).codecs and
   // RTCRtpReceiver.getCapabilities(kind).codecs. For each codec in codecs, If
   // codec is not in codecCapabilities, throw InvalidModificationError.
   for (const auto& codec_preference : codecs) {
     bool is_recv_codec =
         absl::c_any_of(recv_codecs, [&codec_preference](const T& codec) {
           return codec.MatchesCapability(codec_preference);
         });

     bool is_send_codec =
         absl::c_any_of(send_codecs, [&codec_preference](const T& codec) {
           return codec.MatchesCapability(codec_preference);
         });

     if (!is_recv_codec && !is_send_codec) {
       return RTCError(
           RTCErrorType::INVALID_MODIFICATION,
           std::string("Invalid codec preferences: invalid codec with name \"") +
               codec_preference.name + "\".");
     }
   }

   // Check we have a real codec (not just rtx, red or fec)
   if (absl::c_all_of(codecs, [](const RtpCodecCapability& codec) {
         return codec.name == cricket::kRtxCodecName ||
                codec.name == cricket::kRedCodecName ||
                codec.name == cricket::kUlpfecCodecName;
       })) {
     return RTCError(RTCErrorType::INVALID_MODIFICATION,
                     "Invalid codec preferences: codec list must have a non "
                     "RTX, RED or FEC entry.");
   }

   return RTCError::OK();
 }

 }  // namespace

 RtpTransceiver::RtpTransceiver(cricket::MediaType media_type)
     : unified_plan_(false), media_type_(media_type) {
   RTC_DCHECK(media_type == cricket::MEDIA_TYPE_AUDIO ||
              media_type == cricket::MEDIA_TYPE_VIDEO);
 }

 RtpTransceiver::RtpTransceiver(
     rtc::scoped_refptr<RtpSenderProxyWithInternal<RtpSenderInternal>> sender,
     rtc::scoped_refptr<RtpReceiverProxyWithInternal<RtpReceiverInternal>>
         receiver,
     cricket::ChannelManager* channel_manager,
     std::vector<RtpHeaderExtensionCapability> header_extensions_offered)
     : unified_plan_(true),
       media_type_(sender->media_type()),
       channel_manager_(channel_manager),
       HeaderExtensionsToOffer_(std::move(header_extensions_offered)) {
   RTC_DCHECK(media_type_ == cricket::MEDIA_TYPE_AUDIO ||
              media_type_ == cricket::MEDIA_TYPE_VIDEO);
   RTC_DCHECK_EQ(sender->media_type(), receiver->media_type());
   senders_.push_back(sender);
   receivers_.push_back(receiver);
 }

 RtpTransceiver::~RtpTransceiver() {
   Stop();
 }

 void RtpTransceiver::SetChannel(cricket::ChannelInterface* channel) {
   // Cannot set a non-null channel on a stopped transceiver.
   if (stopped_ && channel) {
     return;
   }

   if (channel) {
     RTC_DCHECK_EQ(media_type(), channel->media_type());
   }

   if (channel_) {
     channel_->SignalFirstPacketReceived().disconnect(this);
   }

   channel_ = channel;

   if (channel_) {
     channel_->SignalFirstPacketReceived().connect(
         this, &RtpTransceiver::OnFirstPacketReceived);
   }

   for (const auto& sender : senders_) {
     sender->internal()->SetMediaChannel(channel_ ? channel_->media_channel()
                                                  : nullptr);
   }

   for (const auto& receiver : receivers_) {
     if (!channel_) {
       receiver->internal()->Stop();
     }

     receiver->internal()->SetMediaChannel(channel_ ? channel_->media_channel()
                                                    : nullptr);
   }
 }

 void RtpTransceiver::AddSender(
     rtc::scoped_refptr<RtpSenderProxyWithInternal<RtpSenderInternal>> sender) {
   RTC_DCHECK(!stopped_);
   RTC_DCHECK(!unified_plan_);
   RTC_DCHECK(sender);
   RTC_DCHECK_EQ(media_type(), sender->media_type());
   RTC_DCHECK(!absl::c_linear_search(senders_, sender));
   senders_.push_back(sender);
 }

 bool RtpTransceiver::RemoveSender(RtpSenderInterface* sender) {
   RTC_DCHECK(!unified_plan_);
   if (sender) {
     RTC_DCHECK_EQ(media_type(), sender->media_type());
   }
   auto it = absl::c_find(senders_, sender);
   if (it == senders_.end()) {
     return false;
   }
   (*it)->internal()->Stop();
   senders_.erase(it);
   return true;
 }

 void RtpTransceiver::AddReceiver(
     rtc::scoped_refptr<RtpReceiverProxyWithInternal<RtpReceiverInternal>>
         receiver) {
   RTC_DCHECK(!stopped_);
   RTC_DCHECK(!unified_plan_);
   RTC_DCHECK(receiver);
   RTC_DCHECK_EQ(media_type(), receiver->media_type());
   RTC_DCHECK(!absl::c_linear_search(receivers_, receiver));
   receivers_.push_back(receiver);
 }

 bool RtpTransceiver::RemoveReceiver(RtpReceiverInterface* receiver) {
   RTC_DCHECK(!unified_plan_);
   if (receiver) {
     RTC_DCHECK_EQ(media_type(), receiver->media_type());
   }
   auto it = absl::c_find(receivers_, receiver);
   if (it == receivers_.end()) {
     return false;
   }
   (*it)->internal()->Stop();
   // After the receiver has been removed, there's no guarantee that the
   // contained media channel isn't deleted shortly after this. To make sure that
   // the receiver doesn't spontaneously try to use it's (potentially stale)
   // media channel reference, we clear it out.
   (*it)->internal()->SetMediaChannel(nullptr);
   receivers_.erase(it);
   return true;
 }

 rtc::scoped_refptr<RtpSenderInternal> RtpTransceiver::sender_internal() const {
   RTC_DCHECK(unified_plan_);
   RTC_CHECK_EQ(1u, senders_.size());
   return senders_[0]->internal();
 }

 rtc::scoped_refptr<RtpReceiverInternal> RtpTransceiver::receiver_internal()
     const {
   RTC_DCHECK(unified_plan_);
   RTC_CHECK_EQ(1u, receivers_.size());
   return receivers_[0]->internal();
 }

 cricket::MediaType RtpTransceiver::media_type() const {
   return media_type_;
 }

 absl::optional<std::string> RtpTransceiver::mid() const {
   return mid_;
 }

 void RtpTransceiver::OnFirstPacketReceived(cricket::ChannelInterface*) {
   for (const auto& receiver : receivers_) {
     receiver->internal()->NotifyFirstPacketReceived();
   }
 }

 rtc::scoped_refptr<RtpSenderInterface> RtpTransceiver::sender() const {
   RTC_DCHECK(unified_plan_);
   RTC_CHECK_EQ(1u, senders_.size());
   return senders_[0];
 }

 rtc::scoped_refptr<RtpReceiverInterface> RtpTransceiver::receiver() const {
   RTC_DCHECK(unified_plan_);
   RTC_CHECK_EQ(1u, receivers_.size());
   return receivers_[0];
 }

 void RtpTransceiver::set_current_direction(RtpTransceiverDirection direction) {
   RTC_LOG(LS_INFO) << "Changing transceiver (MID=" << mid_.value_or("<not set>")
                    << ") current direction from "
                    << (current_direction_ ? RtpTransceiverDirectionToString(
                                                 *current_direction_)
                                           : "<not set>")
                    << " to " << RtpTransceiverDirectionToString(direction)
                    << ".";
   current_direction_ = direction;
   if (RtpTransceiverDirectionHasSend(*current_direction_)) {
     has_ever_been_used_to_send_ = true;
   }
 }

 void RtpTransceiver::set_fired_direction(RtpTransceiverDirection direction) {
   fired_direction_ = direction;
 }

 bool RtpTransceiver::stopped() const {
   return stopped_;
 }

 RtpTransceiverDirection RtpTransceiver::direction() const {
   return direction_;
 }

 void RtpTransceiver::SetDirection(RtpTransceiverDirection new_direction) {
   if (stopped()) {
     return;
   }
   if (new_direction == direction_) {
     return;
   }
   direction_ = new_direction;
   SignalNegotiationNeeded();
 }

 absl::optional<RtpTransceiverDirection> RtpTransceiver::current_direction()
     const {
   return current_direction_;
 }

 absl::optional<RtpTransceiverDirection> RtpTransceiver::fired_direction()
     const {
   return fired_direction_;
 }

 void RtpTransceiver::Stop() {
   for (const auto& sender : senders_) {
     sender->internal()->Stop();
   }
   for (const auto& receiver : receivers_) {
     receiver->internal()->Stop();
   }
   stopped_ = true;
   current_direction_ = absl::nullopt;
 }

 RTCError RtpTransceiver::SetCodecPreferences(
     rtc::ArrayView<RtpCodecCapability> codec_capabilities) {
   RTC_DCHECK(unified_plan_);

   // 3. If codecs is an empty list, set transceiver's [[PreferredCodecs]] slot
   // to codecs and abort these steps.
   if (codec_capabilities.empty()) {
     codec_preferences_.clear();
     return RTCError::OK();
   }

   // 4. Remove any duplicate values in codecs.
   std::vector<RtpCodecCapability> codecs;
   absl::c_remove_copy_if(codec_capabilities, std::back_inserter(codecs),
                          [&codecs](const RtpCodecCapability& codec) {
                            return absl::c_linear_search(codecs, codec);
                          });

   // 6. to 8.
   RTCError result;
   if (media_type_ == cricket::MEDIA_TYPE_AUDIO) {
     std::vector<cricket::AudioCodec> recv_codecs, send_codecs;
     channel_manager_->GetSupportedAudioReceiveCodecs(&recv_codecs);
     channel_manager_->GetSupportedAudioSendCodecs(&send_codecs);

     result = VerifyCodecPreferences(codecs, send_codecs, recv_codecs);
   } else if (media_type_ == cricket::MEDIA_TYPE_VIDEO) {
     std::vector<cricket::VideoCodec> recv_codecs, send_codecs;
     channel_manager_->GetSupportedVideoReceiveCodecs(&recv_codecs);
     channel_manager_->GetSupportedVideoSendCodecs(&send_codecs);

     result = VerifyCodecPreferences(codecs, send_codecs, recv_codecs);
   }

   if (result.ok()) {
     codec_preferences_ = codecs;
   }

   return result;
 }

 std::vector<RtpHeaderExtensionCapability>
 RtpTransceiver::HeaderExtensionsToOffer() const {
   return HeaderExtensionsToOffer_;
 }

 }  // namespace webrtc
	/*
	* Copyright 2017 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 "pc/rtp_transceiver.h"

	#include <string>
	#include <utility>

	#include "absl/algorithm/container.h"
	#include "api/rtp_parameters.h"
	#include "pc/channel_manager.h"
	#include "pc/rtp_media_utils.h"
	#include "pc/rtp_parameters_conversion.h"
	#include "rtc_base/checks.h"
	#include "rtc_base/logging.h"

	namespace webrtc {
	namespace {
	template <class T>
	RTCError VerifyCodecPreferences(const std::vector<RtpCodecCapability>& codecs,
	const std::vector<T>& send_codecs,
	const std::vector<T>& recv_codecs) {
	// If the intersection between codecs and
	// RTCRtpSender.getCapabilities(kind).codecs or the intersection between
	// codecs and RTCRtpReceiver.getCapabilities(kind).codecs only contains RTX,
	// RED or FEC codecs or is an empty set, throw InvalidModificationError.
	// This ensures that we always have something to offer, regardless of
	// transceiver.direction.

	if (!absl::c_any_of(codecs, [&recv_codecs](const RtpCodecCapability& codec) {
	return codec.name != cricket::kRtxCodecName &&
	codec.name != cricket::kRedCodecName &&
	codec.name != cricket::kFlexfecCodecName &&
	absl::c_any_of(recv_codecs, [&codec](const T& recv_codec) {
	return recv_codec.MatchesCapability(codec);
	});
	})) {
	return RTCError(RTCErrorType::INVALID_MODIFICATION,
	"Invalid codec preferences: Missing codec from recv "
	"codec capabilities.");
	}

	if (!absl::c_any_of(codecs, [&send_codecs](const RtpCodecCapability& codec) {
	return codec.name != cricket::kRtxCodecName &&
	codec.name != cricket::kRedCodecName &&
	codec.name != cricket::kFlexfecCodecName &&
	absl::c_any_of(send_codecs, [&codec](const T& send_codec) {
	return send_codec.MatchesCapability(codec);
	});
	})) {
	return RTCError(RTCErrorType::INVALID_MODIFICATION,
	"Invalid codec preferences: Missing codec from send "
	"codec capabilities.");
	}

	// Let codecCapabilities be the union of
	// RTCRtpSender.getCapabilities(kind).codecs and
	// RTCRtpReceiver.getCapabilities(kind).codecs. For each codec in codecs, If
	// codec is not in codecCapabilities, throw InvalidModificationError.
	for (const auto& codec_preference : codecs) {
	bool is_recv_codec =
	absl::c_any_of(recv_codecs, [&codec_preference](const T& codec) {
	return codec.MatchesCapability(codec_preference);
	});

	bool is_send_codec =
	absl::c_any_of(send_codecs, [&codec_preference](const T& codec) {
	return codec.MatchesCapability(codec_preference);
	});

	if (!is_recv_codec && !is_send_codec) {
	return RTCError(
	RTCErrorType::INVALID_MODIFICATION,
	std::string("Invalid codec preferences: invalid codec with name \"") +
	codec_preference.name + "\".");
	}
	}

	// Check we have a real codec (not just rtx, red or fec)
	if (absl::c_all_of(codecs, [](const RtpCodecCapability& codec) {
	return codec.name == cricket::kRtxCodecName \|\|
	codec.name == cricket::kRedCodecName \|\|
	codec.name == cricket::kUlpfecCodecName;
	})) {
	return RTCError(RTCErrorType::INVALID_MODIFICATION,
	"Invalid codec preferences: codec list must have a non "
	"RTX, RED or FEC entry.");
	}

	return RTCError::OK();
	}

	} // namespace

	RtpTransceiver::RtpTransceiver(cricket::MediaType media_type)
	: unified_plan_(false), media_type_(media_type) {
	RTC_DCHECK(media_type == cricket::MEDIA_TYPE_AUDIO \|\|
	media_type == cricket::MEDIA_TYPE_VIDEO);
	}

	RtpTransceiver::RtpTransceiver(
	rtc::scoped_refptr<RtpSenderProxyWithInternal<RtpSenderInternal>> sender,
	rtc::scoped_refptr<RtpReceiverProxyWithInternal<RtpReceiverInternal>>
	receiver,
	cricket::ChannelManager* channel_manager,
	std::vector<RtpHeaderExtensionCapability> header_extensions_offered)
	: unified_plan_(true),
	media_type_(sender->media_type()),
	channel_manager_(channel_manager),
	HeaderExtensionsToOffer_(std::move(header_extensions_offered)) {
	RTC_DCHECK(media_type_ == cricket::MEDIA_TYPE_AUDIO \|\|
	media_type_ == cricket::MEDIA_TYPE_VIDEO);
	RTC_DCHECK_EQ(sender->media_type(), receiver->media_type());
	senders_.push_back(sender);
	receivers_.push_back(receiver);
	}

	RtpTransceiver::~RtpTransceiver() {
	Stop();
	}

	void RtpTransceiver::SetChannel(cricket::ChannelInterface* channel) {
	// Cannot set a non-null channel on a stopped transceiver.
	if (stopped_ && channel) {
	return;
	}

	if (channel) {
	RTC_DCHECK_EQ(media_type(), channel->media_type());
	}

	if (channel_) {
	channel_->SignalFirstPacketReceived().disconnect(this);
	}

	channel_ = channel;

	if (channel_) {
	channel_->SignalFirstPacketReceived().connect(
	this, &RtpTransceiver::OnFirstPacketReceived);
	}

	for (const auto& sender : senders_) {
	sender->internal()->SetMediaChannel(channel_ ? channel_->media_channel()
	: nullptr);
	}

	for (const auto& receiver : receivers_) {
	if (!channel_) {
	receiver->internal()->Stop();
	}

	receiver->internal()->SetMediaChannel(channel_ ? channel_->media_channel()
	: nullptr);
	}
	}

	void RtpTransceiver::AddSender(
	rtc::scoped_refptr<RtpSenderProxyWithInternal<RtpSenderInternal>> sender) {
	RTC_DCHECK(!stopped_);
	RTC_DCHECK(!unified_plan_);
	RTC_DCHECK(sender);
	RTC_DCHECK_EQ(media_type(), sender->media_type());
	RTC_DCHECK(!absl::c_linear_search(senders_, sender));
	senders_.push_back(sender);
	}

	bool RtpTransceiver::RemoveSender(RtpSenderInterface* sender) {
	RTC_DCHECK(!unified_plan_);
	if (sender) {
	RTC_DCHECK_EQ(media_type(), sender->media_type());
	}
	auto it = absl::c_find(senders_, sender);
	if (it == senders_.end()) {
	return false;
	}
	(*it)->internal()->Stop();
	senders_.erase(it);
	return true;
	}

	void RtpTransceiver::AddReceiver(
	rtc::scoped_refptr<RtpReceiverProxyWithInternal<RtpReceiverInternal>>
	receiver) {
	RTC_DCHECK(!stopped_);
	RTC_DCHECK(!unified_plan_);
	RTC_DCHECK(receiver);
	RTC_DCHECK_EQ(media_type(), receiver->media_type());
	RTC_DCHECK(!absl::c_linear_search(receivers_, receiver));
	receivers_.push_back(receiver);
	}

	bool RtpTransceiver::RemoveReceiver(RtpReceiverInterface* receiver) {
	RTC_DCHECK(!unified_plan_);
	if (receiver) {
	RTC_DCHECK_EQ(media_type(), receiver->media_type());
	}
	auto it = absl::c_find(receivers_, receiver);
	if (it == receivers_.end()) {
	return false;
	}
	(*it)->internal()->Stop();
	// After the receiver has been removed, there's no guarantee that the
	// contained media channel isn't deleted shortly after this. To make sure that
	// the receiver doesn't spontaneously try to use it's (potentially stale)
	// media channel reference, we clear it out.
	(*it)->internal()->SetMediaChannel(nullptr);
	receivers_.erase(it);
	return true;
	}

	rtc::scoped_refptr<RtpSenderInternal> RtpTransceiver::sender_internal() const {
	RTC_DCHECK(unified_plan_);
	RTC_CHECK_EQ(1u, senders_.size());
	return senders_[0]->internal();
	}

	rtc::scoped_refptr<RtpReceiverInternal> RtpTransceiver::receiver_internal()
	const {
	RTC_DCHECK(unified_plan_);
	RTC_CHECK_EQ(1u, receivers_.size());
	return receivers_[0]->internal();
	}

	cricket::MediaType RtpTransceiver::media_type() const {
	return media_type_;
	}

	absl::optional<std::string> RtpTransceiver::mid() const {
	return mid_;
	}

	void RtpTransceiver::OnFirstPacketReceived(cricket::ChannelInterface*) {
	for (const auto& receiver : receivers_) {
	receiver->internal()->NotifyFirstPacketReceived();
	}
	}

	rtc::scoped_refptr<RtpSenderInterface> RtpTransceiver::sender() const {
	RTC_DCHECK(unified_plan_);
	RTC_CHECK_EQ(1u, senders_.size());
	return senders_[0];
	}

	rtc::scoped_refptr<RtpReceiverInterface> RtpTransceiver::receiver() const {
	RTC_DCHECK(unified_plan_);
	RTC_CHECK_EQ(1u, receivers_.size());
	return receivers_[0];
	}

	void RtpTransceiver::set_current_direction(RtpTransceiverDirection direction) {
	RTC_LOG(LS_INFO) << "Changing transceiver (MID=" << mid_.value_or("<not set>")
	<< ") current direction from "
	<< (current_direction_ ? RtpTransceiverDirectionToString(
	*current_direction_)
	: "<not set>")
	<< " to " << RtpTransceiverDirectionToString(direction)
	<< ".";
	current_direction_ = direction;
	if (RtpTransceiverDirectionHasSend(*current_direction_)) {
	has_ever_been_used_to_send_ = true;
	}
	}

	void RtpTransceiver::set_fired_direction(RtpTransceiverDirection direction) {
	fired_direction_ = direction;
	}

	bool RtpTransceiver::stopped() const {
	return stopped_;
	}

	RtpTransceiverDirection RtpTransceiver::direction() const {
	return direction_;
	}

	void RtpTransceiver::SetDirection(RtpTransceiverDirection new_direction) {
	if (stopped()) {
	return;
	}
	if (new_direction == direction_) {
	return;
	}
	direction_ = new_direction;
	SignalNegotiationNeeded();
	}

	absl::optional<RtpTransceiverDirection> RtpTransceiver::current_direction()
	const {
	return current_direction_;
	}

	absl::optional<RtpTransceiverDirection> RtpTransceiver::fired_direction()
	const {
	return fired_direction_;
	}

	void RtpTransceiver::Stop() {
	for (const auto& sender : senders_) {
	sender->internal()->Stop();
	}
	for (const auto& receiver : receivers_) {
	receiver->internal()->Stop();
	}
	stopped_ = true;
	current_direction_ = absl::nullopt;
	}

	RTCError RtpTransceiver::SetCodecPreferences(
	rtc::ArrayView<RtpCodecCapability> codec_capabilities) {
	RTC_DCHECK(unified_plan_);

	// 3. If codecs is an empty list, set transceiver's [[PreferredCodecs]] slot
	// to codecs and abort these steps.
	if (codec_capabilities.empty()) {
	codec_preferences_.clear();
	return RTCError::OK();
	}

	// 4. Remove any duplicate values in codecs.
	std::vector<RtpCodecCapability> codecs;
	absl::c_remove_copy_if(codec_capabilities, std::back_inserter(codecs),
	[&codecs](const RtpCodecCapability& codec) {
	return absl::c_linear_search(codecs, codec);
	});

	// 6. to 8.
	RTCError result;
	if (media_type_ == cricket::MEDIA_TYPE_AUDIO) {
	std::vector<cricket::AudioCodec> recv_codecs, send_codecs;
	channel_manager_->GetSupportedAudioReceiveCodecs(&recv_codecs);
	channel_manager_->GetSupportedAudioSendCodecs(&send_codecs);

	result = VerifyCodecPreferences(codecs, send_codecs, recv_codecs);
	} else if (media_type_ == cricket::MEDIA_TYPE_VIDEO) {
	std::vector<cricket::VideoCodec> recv_codecs, send_codecs;
	channel_manager_->GetSupportedVideoReceiveCodecs(&recv_codecs);
	channel_manager_->GetSupportedVideoSendCodecs(&send_codecs);

	result = VerifyCodecPreferences(codecs, send_codecs, recv_codecs);
	}

	if (result.ok()) {
	codec_preferences_ = codecs;
	}

	return result;
	}

	std::vector<RtpHeaderExtensionCapability>
	RtpTransceiver::HeaderExtensionsToOffer() const {
	return HeaderExtensionsToOffer_;
	}

	} // namespace webrtc