Add FlexfecSender.

webrtc/modules/rtp_rtcp/include/flexfec_sender.h

+/*
+ *  Copyright (c) 2016 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.
+ */
+
+#ifndef WEBRTC_MODULES_RTP_RTCP_INCLUDE_FLEXFEC_SENDER_H_
+#define WEBRTC_MODULES_RTP_RTCP_INCLUDE_FLEXFEC_SENDER_H_
+
+#include <memory>
+#include <vector>
+
+#include "webrtc/config.h"
+#include "webrtc/base/basictypes.h"
+#include "webrtc/modules/include/module_common_types.h"
+#include "webrtc/modules/rtp_rtcp/source/rtp_packet_to_send.h"
+#include "webrtc/system_wrappers/include/clock.h"
+
+namespace webrtc {
+
+// TODO(brandtr): Update this interface when FlexfecSender is hooked up
+// to PacedSender.
+class FlexfecSender {
+ public:
+  static std::unique_ptr<FlexfecSender> Create(
+      int flexfec_payload_type,
+      uint32_t flexfec_ssrc,
+      uint32_t protected_media_ssrc,
+      const std::vector<RtpExtension>& rtp_header_extensions,
+      Clock* clock);
+  virtual ~FlexfecSender() = default;
+
+  // Sets the FEC rate, max frames sent before FEC packets are sent,
+  // and what type of generator matrices are used.
+  virtual void SetFecParameters(const FecProtectionParams& params) = 0;
+
+  // Adds a media packet to the internal buffer. When enough media packets
+  // have been added, the FEC packets are generated and stored internally.
+  // These FEC packets are then obtained by calling GetFecPackets().
+  // Returns 0 on success, and a negative value if the erasure coding failed.

[danilchap, 2016/10/24 15:29:12]

can it return different negative values?
may be change return value to bool

[brandtr, 2016/10/25 06:39:54]

Nope, can only return from the set {-1,0}. Changing to bool. I should probably
change the underlying code as well.

+  virtual int AddRtpPacketAndGenerateFec(const RtpPacketToSend& packet) = 0;
+
+  // Returns true if there are generated FEC packets available.
+  virtual bool FecAvailable() const = 0;
+
+  // Returns generated FlexFEC packets.
+  virtual std::vector<std::unique_ptr<RtpPacketToSend>> GetFecPackets() = 0;

[danilchap, 2016/10/24 15:29:12]

actually since RtpPacketToSend is inside unique_ptr, you may be can
forward-declare instead of include.
(will make slightly easier for me to move RtpPacketToSend to different module)

[brandtr, 2016/10/25 06:39:54]

Done.

+
+  // Returns the overhead, per packet, for FlexFEC.
+  virtual size_t MaxPacketOverhead() const = 0;
+};
+
+}  // namespace webrtc
+
+#endif  // WEBRTC_MODULES_RTP_RTCP_INCLUDE_FLEXFEC_SENDER_H_