Add packetization and coding/decoding of feedback message format.

webrtc/modules/rtp_rtcp/source/rtcp_packet/feedback_packet.h

+/*
+ *  Copyright (c) 2015 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_SOURCE_RTCP_PACKET_FEEDBACK_PACKET_H_
+#define WEBRTC_MODULES_RTP_RTCP_SOURCE_RTCP_PACKET_FEEDBACK_PACKET_H_
+
+#include <deque>
+#include <vector>
+
+#include "webrtc/base/constructormagic.h"
+#include "webrtc/modules/interface/module_common_types.h"
+#include "webrtc/modules/rtp_rtcp/source/rtcp_packet.h"
+
+namespace webrtc {
+namespace rtcp {
+
+class PacketStatusChunk;
+
+class FeedbackPacket : public RtcpPacket {

[stefan-webrtc, 2015/07/27 11:49:28]

I wonder if maybe we should rename this class to be a bit less generic?

[sprang_webrtc, 2015/07/28 08:28:54]

Renamed to TransportFeedback

+ public:
+  FeedbackPacket();
+  virtual ~FeedbackPacket();
+
+  void WithPacketSenderSsrc(uint32_t ssrc);
+  void WithMediaSourceSsrc(uint32_t ssrc);
+  void WithBase(uint16_t base_sequence,     // Seq# of first packet in this msg.
+                int64_t ref_timestamp_us);  // Reference timestamp for this msg.
+  void WithFeedbackSequenceNumber(uint8_t feedback_sequence);
+  // NOTE: This method require increasing sequence numbers (excepting wraps).

[stefan-webrtc, 2015/07/27 11:49:28]

method requires or methods require :)

[sprang_webrtc, 2015/07/28 08:28:54]

Bah, went too fast..

+  bool WithReceivedPacket(uint16_t sequence_number, int64_t timestamp_us);
+
+  enum class StatusSymbol {
+    kNotReceived,
+    kReceivedSmallDelta,
+    kReceivedLargeDelta,
+  };
+
+  uint16_t GetBaseSequence() const;
+  int32_t GetBaseTime() const;
+  std::vector<FeedbackPacket::StatusSymbol> GetStatusVector() const;
+  std::vector<int16_t> GetReceiveDeltas() const;
+
+  // Get the reference time in microseconds, including any precision loss.
+  int64_t GetBaseTimeUs() const;
+  // Convenience method for getting all deltas as microseconds. The first delta
+  // is relative the base time.
+  std::vector<int64_t> GetReceiveDeltasUs() const;
+
+  static const int kDeltaScaleFactor = 250;  // Convert to multiples of 0.25ms.
+  static const uint8_t kFeedbackMessageType = 15;  // TODO(sprang): IANA reg?
+  static const uint8_t kPayloadType = 205;         // RTPFB, see RFC4585.
+
+  static rtc::scoped_ptr<FeedbackPacket> ParseFrom(const uint8_t* buffer,
+                                                   size_t length);
+
+ protected:
+  bool Create(uint8_t* packet,
+              size_t* position,
+              size_t max_length,
+              PacketReadyCallback* callback) const override;
+
+  size_t BlockLength() const override;
+
+ private:
+  static PacketStatusChunk* ParseChunk(const uint8_t* buffer, size_t max_size);
+
+  int64_t Unwrap(uint16_t sequence_number);
+  bool AddSymbol(StatusSymbol symbol, int64_t seq);
+  bool Encode(StatusSymbol symbol);
+  bool HandleRleCandidate(StatusSymbol symbol,
+                          int current_capacity,
+                          int delta_size);
+  void EmitRemaining();
+  void EmitVectorChunk();
+  void EmitRunLengthChunk();
+
+  uint32_t packet_sender_ssrc_;
+  uint32_t media_source_ssrc_;
+  int32_t base_seq_;
+  int64_t base_time_;
+  uint8_t feedback_seq_;
+  std::vector<PacketStatusChunk*> status_chunks_;
+  std::vector<int16_t> receive_deltas_;
+
+  int64_t last_seq_;
+  int64_t last_timestamp_;
+  std::deque<StatusSymbol> symbol_vec_;
+  uint16_t first_symbol_cardinality_;
+  bool vec_needs_two_bit_symbols_;
+  uint32_t size_bytes_;
+
+  DISALLOW_COPY_AND_ASSIGN(FeedbackPacket);
+};
+
+}  // namespace rtcp
+}  // namespace webrtc
+#endif  // WEBRTC_MODULES_RTP_RTCP_SOURCE_RTCP_PACKET_FEEDBACK_PACKET_H_