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Content for TR 26.980 Word version: 18.0.0

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2 References p. 7

3 Definitions and abbreviations p. 9

3.1 Definitions p. 9

3.2 Abbreviations p. 10

4 Overview p. 10

5 Media Handling in Current 3GPP Conferencing p. 10

6 Use cases p. 12

6.1 Overview p. 12

6.2 Use case A: Transcoding Free Continuous Presence p. 12

6.2.1 Problem Description p. 13

6.2.2 Proposed Solution p. 13

6.3 Use case B: Screen Sharing p. 14

6.3.1 Problem Description p. 14

6.3.2 Proposed Solution p. 15

6.4 Use Case C: Bandwidth Handling p. 17

6.4.1 Problem Description p. 17

6.4.2 Proposed Solution p. 17

6.4.2.1 Single-stream to multi-stream p. 18

6.4.2.2 Multi-stream to single-stream p. 18

6.4.2.3 Multi-stream to multi-stream without bandwidth restriction p. 18

6.4.2.4 Multi-stream to multi-stream with minor bandwidth restrictions p. 19

6.4.2.5 Multi-stream to multi-stream with severe bandwidth restriction p. 20

6.4.2.6 Multi-stream UE to multi-stream UE in point-to-point p. 20

6.5 Use Case D: Active Speaker Override p. 21

6.5.1 Problem Description p. 21

6.5.2 Proposed Solution p. 22

6.6 Use Case E: Pausing Unused Streams p. 23

6.6.1 Problem Description p. 24

6.6.2 Proposed Solution p. 25

6.7 Use Case F: Conference Rate Adaptation Considerations p. 26

6.7.1 Problem Description p. 26

6.7.2 Proposed Solution p. 26

6.8 Use Case G: Multi-stream Audio Steering or Panning p. 29

6.9 Use Case H: De-jitter Buffer Handling p. 30

6.10 Use Case I: Audio Spatialization based on head-tracking p. 31

6.11 Use Case J: Mixing at the Rendering Device - Media Handling, Distribution via Multi-Unicast p. 32

6.11.1 Concurrent Codec Capabilities Exchange p. 32

6.11.1.1 Concurrent Decoding p. 32

6.11.1.2 Concurrent Encoding p. 33

6.11.1.3 Further Considerations in Concurrency p. 34

6.11.1.4 Prioritizing and Ignoring of Received Media Streams p. 34

6.11.1.5 Conclusions p. 34

6.12 Use Case K: Mixing at the Rendering Device - Media Handling, Distribution via Multicast p. 35

6.12.1 Session Establishment p. 35

6.12.1.1 In the presence of a Conference Focus p. 35

6.12.2 Media Handling p. 35

6.12.2.1 In the absence of a Conference Focus for media handling p. 35

6.13 Use Case L: Mixing at the Rendering Device - Media Handling, Distribution via Single Source Multi-Unicast p. 36

6.13.1 Session Establishment p. 38

6.13.2 Media Handling p. 38

6.13.3 Multi-stream Concurrent Encoding/Decoding Capabilities |R14| p. 38

6.13.3.1 Querying and Capabilities Exchange - SIP OPTIONS p. 39

6.13.3.2 Common/Preferred Codec Identification and Usage p. 42

6.13.3.2.1 General p. 42

6.13.3.2.2 Common/Preferred Codec Information Exchange p. 42

6.13.3.2.3 Indicating the Common and Preferred Codec Selection Through SDP p. 43

6.13.4 MSMTSI MRF Handling with Reduced m-lines |R14| p. 43

6.13.4.1 Introduction p. 43

6.13.4.2 RTP Stream Selective Forwarding p. 43

6.14 Use Case M: Provisioning of Talker ID p. 45

6.14.1 Use Case Description p. 45

6.14.2 Problem Description p. 45

6.14.3 Suggested Solution p. 46

6.15 Use Case N: Mixing at the Rendering Device - Media Handling, Concurrent Codec Capabilities Exchange p. 47

6.15.1 Format of the Concurrent Codec Capabilities Information p. 47

6.15.1.1 Using Current SDP Parameters p. 47

6.15.1.2 Using Compact SDP Parameters p. 48

6.15.1.2.1 SDP Line Compression |R14| p. 49

6.15.1.2.2 SDP Line Compression for Terminal Performing Trimming of Streams |R14| p. 51

6.15.1.2.3 Conclusions |R14| p. 51

6.15.2 Protocol for Concurrent Codec Capabilities Exchange (CCCEx) p. 51

6.15.2.1 Recommended Requirements for the CCCEx p. 51

6.15.2.2 Potential Solution for the CCCEx p. 51

6.15.3 Examples of Concurrent Codec Capabilities (CCC) Usage p. 51

6.15.4 Compact CCC SDP Parameter for Session Initiation |R14| p. 56

6.15.4.1 Introduction p. 56

6.15.4.2 Compression Gains p. 56

6.15.4.3 Offer-Answer Rules p. 58

6.15.4.4 Conclusions p. 59

6.16 Use Case O: Media Distribution Without Conference Focus - Session Establishment Aspects p. 59

6.16.1 Session Establishment Without a Conference Focus in Multi-unicast Topology p. 59

6.17 Use Case P: Codec Migration |R14| p. 60

6.17.1 General p. 60

6.17.2 Problem Description p. 60

6.17.3 Proposed Solution p. 61

6.17.3.1 General p. 61

6.17.3.2 Codec Fall-back p. 61

6.17.3.3 Transcoding p. 61

6.17.3.4 Codec Simulcast p. 62

6.17.3.5 Recommended Requirements for Codec Simulcast p. 63

7 Conclusion p. 64

A SDP examples for Multi-stream Multiparty Conference Media Handling p. 65

A.1 General p. 65

A.2 MSMTSI video offer/answer examples p. 65

A.2.1 MSMTSI offer/answer towards an MTSI client p. 65

A.2.2 MSMTSI answer from an MSMTSI MRF p. 67

A.2.3 MSMTSI answer from an MSMTSI client in terminal p. 70

A.2.4 MSMTSI Offer and Answer Using Codec Simulcast |R14| p. 71

A.3 MSMTSI audio offer/answer examples p. 73

A.3.1 MSMTSI offer with multi-stream audio support p. 73

A.3.2 MSMTSI answer with multi-stream audio support p. 74

A.3.3 MSMTSI CCCEx SDP offer/answer example p. 76

B QoS for Multi-stream Multiparty Conference Media Handling |R14| p. 80

B.1 General p. 80

B.2 QoS for MSMTSI video offer/answer examples p. 80

C Technical Background |R14| p. 81

C.1 General p. 81

C.2 Simulcast Stream Identification p. 81

C.2.1 General p. 81

C.2.2 Codec Identification in SDP p. 81

C.2.3 Sampling Identification in SDP p. 82

C.2.4 Bandwidth Identification in SDP p. 82

C.2.5 Simulcast Usage for WebRTC p. 82

C.2.5.1 General p. 82

C.2.5.2 RTP Payload Type Uniqueness p. 82

C.2.5.3 RTP Payload Type Depletion p. 83

C.2.6 Conclusion p. 83

$ Change history p. 84