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// Copyright 2020 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include <memory>
#include <string>
#include <utility>
#include <vector>
#include "cast/common/public/message_port.h"
#include "cast/streaming/answer_messages.h"
#include "cast/streaming/capture_configs.h"
#include "cast/streaming/offer_messages.h"
#include "cast/streaming/sender.h"
#include "cast/streaming/sender_packet_router.h"
#include "cast/streaming/session_config.h"
#include "cast/streaming/session_messager.h"
#include "json/value.h"
#include "util/json/json_serialization.h"
namespace openscreen {
namespace cast {
namespace capture_recommendations {
struct Recommendations;
class Environment;
class Sender;
class SenderSession final {
// Upon successful negotiation, a set of configured senders is constructed
// for handling audio and video. Note that either sender may be null.
struct ConfiguredSenders {
// In practice, we may have 0, 1, or 2 senders configured, depending
// on if the device supports audio and video, and if we were able to
// successfully negotiate a sender configuration.
// If the sender is audio- or video-only, either of the senders
// may be nullptr. However, in the majority of cases they will be populated.
Sender* audio_sender;
AudioCaptureConfig audio_config;
Sender* video_sender;
VideoCaptureConfig video_config;
// The embedder should provide a client for handling the negotiation.
// When the negotiation is complete, the OnNegotiated callback is called.
class Client {
// Called when a new set of senders has been negotiated. This may be
// called multiple times during a session, once for every time Negotiate()
// is called on the SenderSession object. The negotiation call also includes
// capture recommendations that can be used by the sender to provide
// an optimal video stream for the receiver.
virtual void OnNegotiated(
const SenderSession* session,
ConfiguredSenders senders,
capture_recommendations::Recommendations capture_recommendations) = 0;
// Called whenever an error occurs. Ends the ongoing session, and the caller
// must call Negotiate() again if they wish to re-establish streaming.
virtual void OnError(const SenderSession* session, Error error) = 0;
virtual ~Client();
// The SenderSession assumes that the passed in client, environment, and
// message port persist for at least the lifetime of the SenderSession. If
// one of these classes needs to be reset, a new SenderSession should be
// created.
// |message_source_id| and |message_destination_id| are the local and remote
// ID, respectively, to use when sending or receiving control messages (e.g.,
// OFFERs or ANSWERs) over the |message_port|. |message_port|'s SetClient()
// method will be called.
SenderSession(IPAddress remote_address,
Client* const client,
Environment* environment,
MessagePort* message_port,
std::string message_source_id,
std::string message_destination_id);
SenderSession(const SenderSession&) = delete;
SenderSession(SenderSession&&) noexcept = delete;
SenderSession& operator=(const SenderSession&) = delete;
SenderSession& operator=(SenderSession&&) = delete;
// Starts an OFFER/ANSWER exchange with the already configured receiver
// over the message port. The caller should assume any configured senders
// become invalid when calling this method.
Error Negotiate(std::vector<AudioCaptureConfig> audio_configs,
std::vector<VideoCaptureConfig> video_configs);
// We store the current negotiation, so that when we get an answer from the
// receiver we can line up the selected streams with the original
// configuration.
struct Negotiation {
Offer offer;
std::vector<AudioCaptureConfig> audio_configs;
std::vector<VideoCaptureConfig> video_configs;
// Specific message type handler methods.
void OnAnswer(ReceiverMessage message);
// Used by SpawnSenders to generate a sender for a specific stream.
std::unique_ptr<Sender> CreateSender(Ssrc receiver_ssrc,
const Stream& stream,
RtpPayloadType type);
// Helper methods for spawning specific senders from the Answer message.
void SpawnAudioSender(ConfiguredSenders* senders,
Ssrc receiver_ssrc,
int send_index,
int config_index);
void SpawnVideoSender(ConfiguredSenders* senders,
Ssrc receiver_ssrc,
int send_index,
int config_index);
// Spawn a set of configured senders from the currently stored negotiation.
ConfiguredSenders SpawnSenders(const Answer& answer);
// The remote address of the receiver we are communicating with. Used
// for both TLS and UDP traffic.
const IPAddress remote_address_;
// The embedder is expected to provide us a client for notifications about
// negotiations and errors, a valid cast environment, and a messaging
// port for communicating to the Receiver over TLS.
Client* const client_;
Environment* const environment_;
SenderSessionMessager messager_;
// The packet router used for messaging across all senders.
SenderPacketRouter packet_router_;
// Each negotiation has its own sequence number, and the receiver replies
// with the same sequence number that we send. Each message to the receiver
// advances our current sequence number.
int current_sequence_number_ = 0;
// The current negotiation. If present, we are expected an ANSWER from
// the receiver. If not present, any provided ANSWERS are rejected.
std::unique_ptr<Negotiation> current_negotiation_;
// If the negotiation has succeeded, we store the current audio and video
// senders used for this session. Either or both may be nullptr.
std::unique_ptr<Sender> current_audio_sender_;
std::unique_ptr<Sender> current_video_sender_;
}; // namespace cast
} // namespace cast
} // namespace openscreen