S.3 Audio

26.1143GPPIP Multimedia Subsystem (IMS)Media handling and interactionMultimedia telephonyRelease 18TS

S.3.1 General

An MSMTSI client in terminal shall be capable of receiving and may be capable of sending multiple simultaneous audio RTP streams. The number of multiple audio streams received at the MSMTSI client may be different than the number of multiple audio streams sent from the same MSMTSI client.

Support for multiple audio streams in the direction from an MSMTSI MRF to an MSMTSI client in the terminal shall be interpreted as originating from different group call participants.

An MSMTSI client in terminal shall support local mixing of received audio streams, and may support use of spatial rendering tools, such as local Head-Related Transfer Function (HRTF), to perform audio panning and mixing of the multiple audio streams. Audio panning may enable the rendering device to choose to vary the audio levels of participants by adjusting the mixing gains.

Multi-stream audio is not to be confused with multichannel audio where multi-stream audio may include one or more of mono, stereo, or multichannel audio RTP streams originating from different group call participants.

S.3.2 De-jitter buffer

The functional requirements for jitter-buffer management of MSMTSI client in terminal shall meet the same minimum performance requirements per audio stream that are set for MTSI clients (Clause 8).