How Zoom Audio and Video Codecs Affect Bandwidth Usage

Zoom-enabled devices and Zoom products utilize proprietary codec technology to adapt to network conditions and CPU usage

Zoom’s Adaptive Codec at the application layer optimizes performance with what we call the “Reactive QoS Layer.” The Zoom application will adjust the video streams temporally (frames per second) and spatially (resolution).

Example

If the Zoom Workplace desktop app is sending 720P resolution at 30 frames per second and the Reactive QOS layer detects that the CPU is highly utilized, the app will attempt to keep the same resolution but adjust to 15 frames per second to reduce the load on the CPU. If the Reactive QOS layer detects that the network I/O of the device itself is a bottleneck the Adaptive Codec will drop the resolution of all send/receive video streams to work within the available bandwidth. Taking these actions helps preserve audio for intelligible communication at low bandwidth.

Zoom uses industry-leading audio and video codecs to maintain high-quality media during varying network conditions and video layouts

The following table shows which audio and video software codecs are utilized by Zoom applications and Zoom-enabled devices.

Zoom Product	H.264 scalable video codec	Opus audio codec	SILK audio codec
Zoom Workplace desktop app	✔	✔	✔
Zoom Workplace mobile app	✔	✔	✔
Zoom Workplace VDI app	✔	✔	✔
Zoom Rooms	✔	✔	✔
Zoom Phone		✔	✔
Zoom Contact Center	✔	✔	✔

The H.264 Scalable Video Codec adapts to video layouts, resolutions, and the video resolutions of other meeting participants

As more participants join a Zoom meeting, their Zoom applications will request certain video resolutions from the Zoom app that you are using. These requested resolutions will vary in quality based on the remote meeting participant’s selected video layouts. Your Zoom application can transmit up to four H.264 SVC (Scalable Video Codec) video streams simultaneously to accommodate different resolutions requested by participants on the far end. The H.264 SVC also adapts to your video settings for content sharing and layout.

Opus and SILK codecs are used for audio communications in Zoom Meetings and Webinars and for Zoom Phone and Zoom Contact Center

SILK and Opus audio codecs are adaptive, dynamically adjusting their bitrates to real-time network conditions to provide the best voice communication quality. Recommended audio bandwidth allotments in this document are provided in ranges, given the dynamic function of these codecs