Using CDN for Live Streaming

Overview

ZEGO Express SDK supports publishing streams to CDN (Content Delivery Network), including two functions: relaying to CDN and direct publishing to CDN. Based on this functionality, developers can connect RTC products and CDN live streaming products, making it convenient for users to watch and listen to live content directly from web pages or third-party players. To ensure security, CDN authentication is enabled by default when publishing to CDN.

To prevent attackers from stealing or forging your publishing URL, you can refer to CDN Stream Publishing Authentication to improve the security of your stream publishing usage.

Relaying to CDN

Relaying to CDN refers to the process of pushing audio and video streams from ZEGO audio and video cloud to ZEGO's own CDN or third-party CDNs.

Relaying to CDN includes the following three methods:

Direct Publishing to CDN

Direct publishing to CDN refers to the process of pushing audio and video streams directly from the local client to the CDN. Users can watch directly from web pages or third-party players through the Play stream URL. However, since the direct CDN publishing function does not go through the ZEGOCLOUD during network transmission, developers cannot use ZEGO's real-time audio and video services.

Feature Comparison

The descriptions and usage scenarios of the two functions are as follows:

Prerequisites

Before using CDN for live streaming, please ensure:

• You have integrated ZEGO Express SDK into your project and implemented basic real-time audio and video functions. For details, please refer to Quick Start - Integration and Quick Start - Implementation.
• You have created a project in the ZEGOCLOUD Console and applied for a valid AppID and AppSign. For details, please refer to Console - Project Information.

Demo Source Code Download

Please refer to Download Demo Source Code to obtain the source code.

For related source code, please check the files in the "lib/topics/StreamAdvanced/stream_by_cdn" directory.

Relaying to CDN

Initialization and Login Room

Please refer to "Create Engine" and "Login Room" in Quick Start - Implementation.

Start Publishing Stream

Please refer to "Stream Publishing" in Quick Start - Implementation.

Start Relaying

After stream publishing is successful, call the addPublishCdnUrl interface to add the URL for dynamic relaying to CDN. You can dynamically relay the audio and video streams that have been successfully published to the ZEGO real-time cloud to third-party CDNs. The supported relay address format is "rtmp".

// After stream publishing is successful, start relaying to CDN

// Stream ID used when publishing
String streamID = "STREAM_ID";
// CDN address to be relayed, please fill in the actual URL, streamID is the stream name for publishing, can be customized
String URL = "rtmp://domain-name ingest-point/streamID";
ZegoExpressEngine.instance.addPublishCdnUrl(streamID, URL).then((ZegoPublisherUpdateCdnUrlResult result) {
    if(result.errorCode == 0) {
        // Relay successful
    } else {
        // Relay failed, possibly due to network reasons causing the relay request to fail
    }
});

// After stream publishing is successful, start relaying to CDN

// Stream ID used when publishing
String streamID = "STREAM_ID";
// CDN address to be relayed, please fill in the actual URL, streamID is the stream name for publishing, can be customized
String URL = "rtmp://domain-name ingest-point/streamID";
ZegoExpressEngine.instance.addPublishCdnUrl(streamID, URL).then((ZegoPublisherUpdateCdnUrlResult result) {
    if(result.errorCode == 0) {
        // Relay successful
    } else {
        // Relay failed, possibly due to network reasons causing the relay request to fail
    }
});

(Optional) Listen for CDN Relay Status Notifications

Add/Remove Relay CDN Address Status Callback

Developers can register onPublisherRelayCDNStateUpdate to get the add/remove relay CDN address status callback. After the ZEGO RTC server relays the audio and video stream to the CDN, if the CDN relay status changes, such as relay stopping or relay retrying, this callback will be received.

ZegoExpressEngine.onPublisherRelayCDNStateUpdate =
 (String streamID, List<ZegoStreamRelayCDNInfo> infoList) {
};

ZegoExpressEngine.onPublisherRelayCDNStateUpdate =
 (String streamID, List<ZegoStreamRelayCDNInfo> infoList) {
};

Relay CDN Information Details

Relay CDN information ZegoStreamRelayCDNInfo includes the URL of the CDN stream publishing, relay status, reason for relay status change, and time when the status occurred. All parameters in ZegoStreamRelayCDNInfo are as follows:

Among them, the values for state are as follows:

The values for updateReason are as follows:

Stop Relaying

Call the removePublishCdnUrl interface to delete the URL for dynamic relaying to CDN. When calling the removePublishCdnUrl interface to stop relaying, please ensure that the current stream streamID exists.

// Stream ID used when publishing
String streamID = "STREAM_ID";
// CDN address to stop relaying, please fill in the actual URL, streamID is the stream name for publishing
String URL = "rtmp://domain-name ingest-point/streamID";
ZegoExpressEngine.instance.removePublishCdnUrl(streamID, URL).then((ZegoPublisherUpdateCdnUrlResult result) {
    if(result.errorCode == 0) {
        // Stop relay successful
    } else {
        // Stop relay failed, possibly due to network reasons causing the stop relay request to fail
    }
});

// Stream ID used when publishing
String streamID = "STREAM_ID";
// CDN address to stop relaying, please fill in the actual URL, streamID is the stream name for publishing
String URL = "rtmp://domain-name ingest-point/streamID";
ZegoExpressEngine.instance.removePublishCdnUrl(streamID, URL).then((ZegoPublisherUpdateCdnUrlResult result) {
    if(result.errorCode == 0) {
        // Stop relay successful
    } else {
        // Stop relay failed, possibly due to network reasons causing the stop relay request to fail
    }
});

Direct Publishing to CDN

Start Direct Publishing to CDN

Before publishing stream, call the enablePublishDirectToCDN interface to publish audio and video streams directly to CDN.

// URL needs to be filled in by the developer based on the actual situation, streamID is the stream name for publishing, can be customized
String url = "rtmp://domain-name ingest-point/streamID";
var config = new ZegoCDNConfig(url, "");

ZegoExpressEngine.instance.enablePublishDirectToCDN(true, config: config);
ZegoExpressEngine.instance.startPublishingStream("STREAM_ID");

// URL needs to be filled in by the developer based on the actual situation, streamID is the stream name for publishing, can be customized
String url = "rtmp://domain-name ingest-point/streamID";
var config = new ZegoCDNConfig(url, "");

ZegoExpressEngine.instance.enablePublishDirectToCDN(true, config: config);
ZegoExpressEngine.instance.startPublishingStream("STREAM_ID");

Stop Direct Publishing to CDN

If you need to stop direct publishing to CDN, call the stopPublishingStream interface to stop publishing.

After stopping publishing, if the next publishing does not need direct CDN publishing, you can call the enablePublishDirectToCDN interface and pass the value "false" to turn off the direct CDN publishing function. Calling this interface during publishing will not affect this publishing.

ZegoExpressEngine.instance.stopPublishingStream();
// URL needs to be filled in by the developer based on the actual situation, streamID is the stream name for publishing, can be customized
String url = "rtmp://domain-name ingest-point/streamID";
var config = new ZegoCDNConfig(url, "");
ZegoExpressEngine.instance.enablePublishDirectToCDN(false, config: config);

ZegoExpressEngine.instance.stopPublishingStream();
// URL needs to be filled in by the developer based on the actual situation, streamID is the stream name for publishing, can be customized
String url = "rtmp://domain-name ingest-point/streamID";
var config = new ZegoCDNConfig(url, "");
ZegoExpressEngine.instance.enablePublishDirectToCDN(false, config: config);

Audience Playing Stream

• When the publisher publishes directly to CDN, the playing side can play the stream directly through streamID. Please refer to "Playing Stream" in Quick Start - Implementation.

• After the audio and video stream is successfully relayed to CDN, when developers want users to play from CDN, they need to use the custom URL playing method instead of playing through stream ID. For URL playing operation steps, please refer to "1 Configure Playing Parameters" and "2 Start Playing" in Playing Stream by URL.