Simulcast Definition: The Tech Behind Efficient Meetings

Media and its transmission have undergone significant transformation in recent years. Just up to one decade ago, it was almost unimaginable that people could easily stream videos or audio from their small-screen devices to big-screen TVs. Whether you’re watching a movie, or sharing video content for a lecture or a conference, Chromecast enhances your viewing experience. Now, you can easily chromecast Macbook to tv and make the files visible on the big screen.

However, technologies evolved even more, and today people can launch their own media channels and broadcast them across a wide audience via multiple platforms.

Suppose you want to start a broadcast, but your viewers are using different platforms. Would you really have to make a choice between TikTok vs YouTube, Instagram vs TikTok, etc.  Not at all! Simulcast streaming technology allows you to run a simultaneous live broadcast for different applications from the same platform. Let’s clarify what this means.

What is simulcasting?

Simulcast is the synchronous broadcasting of programs or events through multiple services using real-time messaging protocol (RTMP). For example, broadcasting a soccer match simultaneously on TV and radio is a simulcast.

The term ”simulcast” came from America when NBC and CBS began broadcasting several programs simultaneously on both radio and TV in 1948. Today’s simulcast refers to content that is shared digitally through websites and social platforms. Virtual events, webinars, speeches, sporting events, or content created for entertainment purposes can be streamed simultaneously to multiple platforms. To capture these events professionally, consider hiring an event photographer. For the simulcast system, special repeaters are installed that allow the system to operate stably over long distances.

Simulcast is a video conferencing architecture with the following data transmission procedure between the server and the endpoints:

1. The server receives several (3-5) video streams from each client containing the camera image in various resolutions and quality.
2. The server sends a video stream copy of the other participants that corresponds to the bandwidth and device capabilities of each endpoint.

How does a simulcast work?

This architecture is a good choice when the layout puts one participant in the bigger video window, while others are displayed in smaller panes.

Simulcast architecture advantages

• Several levels of quality allow for some flexibility as compared to earlier VC architectures.
• Saves the server from processing  video.

Simulcast  architecture disadvantages

• In real life Simulcast rarely manages to use channels and resources efficiently because the image in all streams is transmitted the same, simply with different levels of detail. Redundancy occurs because each participant in the conference sends a larger stream than necessary.
• Simulcast-based systems require significant resources from user’s VC endpoints, but use them inefficiently. In such systems the main network load falls on the endpoints, which is caused by the need for simultaneous support of multiple levels of video quality. This can lead to performance issues, including CPU thermal throttling, affecting the stability of the streaming experience.

Comparison: 4 participants, on the endpoint

Comparison: 4 participants, on the server

Simulcast has been replaced by SVC architecture, which allows changing video quality without creating explicit copies.

What is the difference between simulcasting and multicasting?

Simply put, both of these systems transmit the same signal simultaneously from different sites, but simulcast does so on the same frequency and multicast on different frequencies.