Using CDN for Live Streaming

Feature Overview

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

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

Relay to CDN

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

Relay to CDN includes the following three methods:

Direct Publish to CDN

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

Feature Comparison

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

Prerequisites

Before using CDN for live streaming, ensure that:

• You have created a project in the ZEGOCLOUD Console and applied for a valid AppID and AppSign. For details, see Console - Project Information.
• You have integrated the ZEGO Express SDK into your project and implemented basic audio/video publishing and playing functionality. For details, see Quick Start - Integration and Quick Start - Implementation Flow.

Example Source Code Download

Please refer to Download Example Source Code to get the source code.

For related source code, please view files in the "/ZegoExpressExample/Examples/AdvancedStreaming/StreamByCDN" directory.

Relay to CDN

1 Initialize and Log In to Room

Please refer to "Create Engine" and "Log In to Room" in Quick Start - Implementation Flow.

2 Start Publishing Stream

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

3 Start Relaying

After the stream is successfully published, call the addPublishCdnUrl interface to add a URL for dynamic relaying to CDN, so that the audio/video stream that has been successfully published to the ZEGO real-time cloud can be dynamically relayed to third-party CDNs. The supported relay address format is "rtmp".

// After the stream is successfully published, start relaying to CDN

// Stream ID used when publishing
NSString *streamID = @"STREAM_ID";
// CDN address to relay, please fill in according to the actual URL, streamID is the stream name for publishing, can be customized
NSString *URL = @"rtmp://publish_domain/ingest_point/streamID";
[self.engine addPublishCDNURL:URL stream:streamID callback:^(int errorCode) {
    // Get notification of whether relaying to CDN was successful
    if(errorCode == 0) {
        // Relay successful
    } else {
        // Relay failed, possibly due to network reasons causing the relay request to fail
    }
}];

// After the stream is successfully published, start relaying to CDN

// Stream ID used when publishing
NSString *streamID = @"STREAM_ID";
// CDN address to relay, please fill in according to the actual URL, streamID is the stream name for publishing, can be customized
NSString *URL = @"rtmp://publish_domain/ingest_point/streamID";
[self.engine addPublishCDNURL:URL stream:streamID callback:^(int errorCode) {
    // Get notification of whether relaying to CDN was successful
    if(errorCode == 0) {
        // Relay successful
    } else {
        // Relay failed, possibly due to network reasons causing the relay request to fail
    }
}];

4 (Optional) Listen to CDN Relay Status Notification

Add/Remove Relay CDN Address Status Callback

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

- (void)onPublisherRelayCDNStateUpdate:(NSArray<ZegoStreamRelayCDNInfo *> *)infoList streamID:(NSString *)streamID {
}

- (void)onPublisherRelayCDNStateUpdate:(NSArray<ZegoStreamRelayCDNInfo *> *)infoList streamID:(NSString *)streamID {
}

Relay CDN Information Details

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

Among them, state values are as follows:

updateReason values are as follows:

5 Stop Relaying

Call removePublishCdnUrl to remove 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
NSString *streamID = @"STREAM_ID";
// CDN address to stop relaying, please fill in according to the actual URL, streamID is the stream name for publishing
NSString *URL = @"rtmp://publish_domain/ingest_point/streamID";
[self.engine removePublishCDNURL:URL stream:streamID callback:^(int errorCode) {
    // Get notification of whether stopping relaying to CDN was successful
    if(errorCode == 0) {
        // Stop relaying successful
    } else {
        // Stop relaying failed, possibly due to network reasons causing the stop relaying request to fail
    }
}];

// Stream ID used when publishing
NSString *streamID = @"STREAM_ID";
// CDN address to stop relaying, please fill in according to the actual URL, streamID is the stream name for publishing
NSString *URL = @"rtmp://publish_domain/ingest_point/streamID";
[self.engine removePublishCDNURL:URL stream:streamID callback:^(int errorCode) {
    // Get notification of whether stopping relaying to CDN was successful
    if(errorCode == 0) {
        // Stop relaying successful
    } else {
        // Stop relaying failed, possibly due to network reasons causing the stop relaying request to fail
    }
}];

Direct Publish to CDN

1 Start Direct Publish to CDN

Call the enablePublishDirectToCDN interface before publishing to push audio/video streams directly to CDN.

ZegoCDNConfig *config = [[ZegoCDNConfig alloc] init];
// URL needs to be filled in by the developer according to the actual situation, streamID is the stream name for publishing, can be customized
config.URL = @"rtmp://publish_domain/ingest_point/streamID";
[self.engine enablePublishDirectToCDN:YES config:config];
[self.engine startPublishing:@"STREAM_ID"];

ZegoCDNConfig *config = [[ZegoCDNConfig alloc] init];
// URL needs to be filled in by the developer according to the actual situation, streamID is the stream name for publishing, can be customized
config.URL = @"rtmp://publish_domain/ingest_point/streamID";
[self.engine enablePublishDirectToCDN:YES config:config];
[self.engine startPublishing:@"STREAM_ID"];

2 Stop Direct Publish to CDN

To stop direct publish to CDN, call the stopPublishingStream interface to stop publishing.

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

[[ZegoExpressEngine sharedEngine] stopPublishingStream];
ZegoCDNConfig *config = [[ZegoCDNConfig alloc] init];
[[ZegoExpressEngine sharedEngine] enablePublishDirectToCDN:NO config:config];

[[ZegoExpressEngine sharedEngine] stopPublishingStream];
ZegoCDNConfig *config = [[ZegoCDNConfig alloc] init];
[[ZegoExpressEngine sharedEngine] enablePublishDirectToCDN:NO config:config];

Audience Playing Stream

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

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