Multi-stream Multiparty Video Conferencing

Description

Multi-stream Multiparty Video Conferencing (MMVC) is a standardized service defined by 3GPP that significantly enhances traditional video conferencing. It operates by establishing a centralized media processing function, often within an application server or a dedicated Multimedia Resource Function (MRF) in the IP Multimedia Subsystem (IMS) core. Unlike legacy conferencing where a single composite video mix is sent to all participants, MMVC allows the conference server to generate and manage multiple independent media streams for each participant. This includes separate streams for each active speaker, a presentation stream, and potentially streams for different camera angles or layouts. The key architectural component is the Media Control Function, which negotiates capabilities with user equipment, manages the mixing and routing of these multiple streams, and handles floor control for speaking privileges.

The service works by utilizing the Session Initiation Protocol (SIP) and the Session Description Protocol (SDP) for session establishment and media negotiation. During session setup, the User Equipment (UE) indicates its support for MMVC and its capability to decode multiple simultaneous Real-time Transport Protocol (RTP) streams. The network's conference focus, typically an IMS Application Server (AS), coordinates the session. It instructs the media processing resource on which streams to create, encode, and forward to each participant based on their requests and network conditions. This allows a participant, for example, to choose a main view of the current speaker while having a secondary picture-in-picture view of a shared presentation, all delivered as separate RTP streams.

The role of MMVC in the network is to provide a rich, flexible, and personalized conferencing experience that leverages the increasing bandwidth and processing power of mobile devices. It shifts complexity from the endpoint to the network, enabling advanced features on simpler devices. The service integrates with core IMS functions like the Call Session Control Function (CSCF) for routing and the Home Subscriber Server (HSS) for service profile data. It also interfaces with policy control (PCRF/PCF) to ensure appropriate Quality of Service (QoS) for the multiple high-bandwidth streams, making it a key enabler for professional-grade mobile collaboration.

Purpose & Motivation

MMVC was created to address the limitations of traditional 3G-324M-based or early IMS video telephony conferencing, which typically provided a single, fixed video composition (a 'video mix') to all participants. This old model offered no personalization, wasted bandwidth by sending unwanted video content, and provided a poor user experience, especially in meetings with many participants or multiple content sources. The rise of high-speed LTE networks and powerful smartphones created a demand for business and consumer video conferencing services that could rival or integrate with popular over-the-top (OTT) applications.

The primary problem MMVC solves is the lack of user control and layout flexibility in mobile network-provided conferencing. By standardizing a multi-stream approach, 3GPP enabled network operators to offer a competitive, carrier-grade service. This allows participants to choose their own view (e.g., active speaker, gallery, or presentation focus), which is crucial for effective remote collaboration. Furthermore, it optimizes network resource usage by allowing the network to send only the streams a user has selected, rather than a single high-bitrate composite of all video sources. Its creation was motivated by the need for operators to move beyond basic voice and SMS, leveraging their IMS investments to offer advanced, value-added multimedia services that generate new revenue streams and reduce customer churn.

Key Features

• Simultaneous transmission of multiple independent RTP video streams to a single endpoint
• Dynamic participant-controlled layout and stream selection (e.g., active speaker, presentation view)
• Network-based media processing and mixing, reducing endpoint complexity
• Integration with IMS core for session control, authentication, and charging
• Support for floor control mechanisms to manage speaking rights
• Quality of Service (QoS) negotiation and policy enforcement for multiple media flows

Evolution Across Releases

Defining Specifications