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