1*3f982cf4SFabien Sanglard // Copyright 2019 The Chromium Authors. All rights reserved. 2*3f982cf4SFabien Sanglard // Use of this source code is governed by a BSD-style license that can be 3*3f982cf4SFabien Sanglard // found in the LICENSE file. 4*3f982cf4SFabien Sanglard 5*3f982cf4SFabien Sanglard #ifndef CAST_STREAMING_SSRC_H_ 6*3f982cf4SFabien Sanglard #define CAST_STREAMING_SSRC_H_ 7*3f982cf4SFabien Sanglard 8*3f982cf4SFabien Sanglard #include <stdint.h> 9*3f982cf4SFabien Sanglard 10*3f982cf4SFabien Sanglard namespace openscreen { 11*3f982cf4SFabien Sanglard namespace cast { 12*3f982cf4SFabien Sanglard 13*3f982cf4SFabien Sanglard // A Synchronization Source is a 32-bit opaque identifier used in RTP packets 14*3f982cf4SFabien Sanglard // for identifying the source (or recipient) of a logical sequence of encoded 15*3f982cf4SFabien Sanglard // audio/video frames. In other words, an audio stream will have one sender SSRC 16*3f982cf4SFabien Sanglard // and a video stream will have a different sender SSRC. 17*3f982cf4SFabien Sanglard using Ssrc = uint32_t; 18*3f982cf4SFabien Sanglard 19*3f982cf4SFabien Sanglard // The "not set" or "null" value for the Ssrc type. 20*3f982cf4SFabien Sanglard constexpr Ssrc kNullSsrc{0}; 21*3f982cf4SFabien Sanglard 22*3f982cf4SFabien Sanglard // Computes a new SSRC that will be used to uniquely identify an RTP stream. The 23*3f982cf4SFabien Sanglard // |higher_priority| argument, if true, will generate an SSRC that causes the 24*3f982cf4SFabien Sanglard // system to use a higher priority when scheduling data transmission. Generally, 25*3f982cf4SFabien Sanglard // this is set to true for audio streams and false for video streams. 26*3f982cf4SFabien Sanglard Ssrc GenerateSsrc(bool higher_priority); 27*3f982cf4SFabien Sanglard 28*3f982cf4SFabien Sanglard // Returns a value indicating how to prioritize data transmission for a stream 29*3f982cf4SFabien Sanglard // with |ssrc_a| versus a stream with |ssrc_b|: 30*3f982cf4SFabien Sanglard // 31*3f982cf4SFabien Sanglard // ret < 0: Stream |ssrc_a| has higher priority. 32*3f982cf4SFabien Sanglard // ret == 0: Equal priority. 33*3f982cf4SFabien Sanglard // ret > 0: Stream |ssrc_b| has higher priority. 34*3f982cf4SFabien Sanglard int ComparePriority(Ssrc ssrc_a, Ssrc ssrc_b); 35*3f982cf4SFabien Sanglard 36*3f982cf4SFabien Sanglard } // namespace cast 37*3f982cf4SFabien Sanglard } // namespace openscreen 38*3f982cf4SFabien Sanglard 39*3f982cf4SFabien Sanglard #endif // CAST_STREAMING_SSRC_H_ 40