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+/*
+ *  Copyright 2018 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 MEDIA_BASE_RID_DESCRIPTION_H_
+#define MEDIA_BASE_RID_DESCRIPTION_H_
+
+#include <map>
+#include <string>
+#include <vector>
+
+namespace cricket {
+
+enum class RidDirection { kSend, kReceive };
+
+// Description of a Restriction Id (RID) according to:
+// https://tools.ietf.org/html/draft-ietf-mmusic-rid-15
+// A Restriction Identifier serves two purposes:
+//   1. Uniquely identifies an RTP stream inside an RTP session.
+//      When combined with MIDs (https://tools.ietf.org/html/rfc5888),
+//      RIDs uniquely identify an RTP stream within an RTP session.
+//      The MID will identify the media section and the RID will identify
+//      the stream within the section.
+//      RID identifiers must be unique within the media section.
+//   2. Allows indicating further restrictions to the stream.
+//      These restrictions are added according to the direction specified.
+//      The direction field identifies the direction of the RTP stream packets
+//      to which the restrictions apply. The direction is independent of the
+//      transceiver direction and can be one of {send, recv}.
+//      The following are some examples of these restrictions:
+//        a. max-width, max-height, max-fps, max-br, ...
+//        b. further restricting the codec set (from what m= section specified)
+//
+// Note: Indicating dependencies between streams (using depend) will not be
+// supported, since the WG is adopting a different approach to achieve this.
+// As of 2018-12-04, the new SVC (Scalable Video Coder) approach is still not
+// mature enough to be implemented as part of this work.
+// See: https://w3c.github.io/webrtc-svc/ for more details.
+struct RidDescription final {
+  RidDescription();
+  RidDescription(const std::string& rid, RidDirection direction);
+  RidDescription(const RidDescription& other);
+  ~RidDescription();
+  RidDescription& operator=(const RidDescription& other);
+
+  // This is currently required for unit tests of StreamParams which contains
+  // RidDescription objects and checks for equality using operator==.
+  bool operator==(const RidDescription& other) const;
+  bool operator!=(const RidDescription& other) const {
+    return !(*this == other);
+  }
+
+  // The RID identifier that uniquely identifies the stream within the session.
+  std::string rid;
+
+  // Specifies the direction for which the specified restrictions hold.
+  // This direction is either send or receive and is independent of the
+  // direction of the transceiver.
+  // https://tools.ietf.org/html/draft-ietf-mmusic-rid-15#section-4 :
+  // The "direction" field identifies the direction of the RTP Stream
+  // packets to which the indicated restrictions are applied.  It may be
+  // either "send" or "recv".  Note that these restriction directions are
+  // expressed independently of any "inactive", "sendonly", "recvonly", or
+  // "sendrecv" attributes associated with the media section.  It is, for
+  // example, valid to indicate "recv" restrictions on a "sendonly"
+  // stream; those restrictions would apply if, at a future point in time,
+  // the stream were changed to "sendrecv" or "recvonly".
+  RidDirection direction;
+
+  // The list of codec payload types for this stream.
+  // It should be a subset of the payloads supported for the media section.
+  std::vector<int> payload_types;
+
+  // Contains key-value pairs for restrictions.
+  // The keys are not validated against a known set.
+  // The meaning to infer for the values depends on each key.
+  // Examples:
+  // 1. An entry for max-width will have a value that is interpreted as an int.
+  // 2. An entry for max-bpp (bits per pixel) will have a float value.
+  // Interpretation (and validation of value) is left for the implementation.
+  // I.E. the media engines should validate values for parameters they support.
+  std::map<std::string, std::string> restrictions;
+};
+
+}  // namespace cricket
+
+#endif  // MEDIA_BASE_RID_DESCRIPTION_H_