Configure bandwidth management

Introduction

This document describes how to enable and configure the traffic control feature for ZEGOCLOUD’s SDKs.

Network conditions can change at any time during a call or a live streaming session. To maintain smooth stream publishing even when network conditions degrade, you can enable the traffic control feature of the SDK to dynamically adjust the uplink bitrate to adapt to the current network conditions. At the same time, you can also specify which of the following encoding parameters should be changed to adjust the uplink bitrate：

• Video bitrate
• Video frame rate
• Video resolution
• Audio bitrate

If the estimated uplink bandwidth is lower than the configured stream publishing bitrate, the SDK gradually lowers the specified parameters to reduce the uplink bitrate. When the network conditions improve, the SDK then adjusts those parameters to bring the uplink bitrate back to the configured value.

In one-on-one real-time interactions, the SDK automatically enables downlink traffic control. In such cases, the SDK on the stream subscriber side sends the information of the downlink network conditions to the stream publisher. The SDK on the stream publisher side then adjusts its uplink bitrate to fit the lower one of the estimated uplink bandwidth of its own and the estimated downlink bandwidth of the stream subscriber.

Prerequisites

Before you begin, make sure you complete the following:

• Create a project in ZEGOCLOUD Admin Console and get the AppID and AppSign of your project.

• Refer to the Quick Start doc to complete the SDK integration and basic function implementation.

Enable traffic control

To enable traffic control, call the enableTrafficControl method before publishing any stream.

Here are some notes about how to set up the parameters of the method:

• The first parameter enable is a boolean. Set it to true to enable traffic control.
• The second parameter property is an enum value of ZegoTrafficControlProperty. The default value is ADAPTIVE_FPS, which means the SDK adjusts the uplink bitrate by adjusting the video frame rate. You can decide how to set up the traffic control property based on the needs of your use case. For example:
  • For social live streaming use cases, video smoothness takes priority over video quality. You can set property to ADAPTIVE_RESOLUTION, which means the SDK adjusts the uplink bitrate by adjusting the video resolution.
  • For online classroom use cases, video quality is usually more important. You can set property to ADAPTIVE_FPS, which means the SDK lowers the video frame rate but maintains the video quality when it needs to lower the uplink bitrate.
  • You can specify more than one value to the property parameter as needed.

// Enable traffic control, and adjust the uplink bitrate by adjusting both the video resolution and frame rate.
ZegoExpressEngine.getEngine().enableTrafficControl(true, ADAPTIVE_RESOLUTION.value() | ADAPTIVE_FPS.value());

Advanced settings

You can call the setMinVideoBitrateForTrafficControl method to set up a minimum video bitrate and specify what the SDK should do when the uplink bandwidth is not sufficient for this minimal video bitrate.

Similarly, you can call the setMinVideoFpsForTrafficControl and setMinVideoResolutionForTrafficControl methods to set up a minimum video frame rate and minimum resolution.

// After traffic control is enabled, when the uplink bandwidth is lower than 200kbps, continue to send video data at a very low frame rate.
ZegoExpressEngine.getEngine().setMinVideoBitrateForTrafficControl(200, ZegoTrafficControlMinVideoBitrateMode.ULTRA_LOW_FPS);