Using CDN for Live Streaming

Feature 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 function, developers can integrate RTC products and CDN live streaming products, making it convenient for users to directly watch and listen to live content 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 publishing usage.

Relaying to CDN

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

Relaying to CDN includes the following three methods:

Direct Publishing to CDN

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

Function Comparison

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

Prerequisites

Before using CDN for live streaming, please ensure:

• 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.
• You have integrated ZEGO Express SDK in the project and implemented basic audio/video publishing and playing functions. For details, please refer to Quick Start - Integration and Quick Start - Implementation Flow.

Usage Steps

Relaying to CDN

Initialize, Login Room, Start Publishing Stream

Please refer to "Create Engine", "Login Room", "Publish Stream" in Quick Start - Implementation Flow.

Start Relaying

After publishing stream successfully, call the addPublishCdnUrl interface to add the URL for dynamic relaying to CDN, so that the audio/video stream that has been successfully published to ZEGO real-time cloud can be dynamically relayed to third-party CDN.

• Call example:

  // After publishing stream successfully, start relaying to CDN
  
  // Stream ID used when publishing
  std::string streamID = "STREAM_ID";
  // CDN address to be relayed, please fill in according to the actual URL, streamID is the stream name of publishing, can be customized
  std::string URL = "rtmp://publish_domain/entry_point/streamID";
  
  engine->addPublishCdnUrl(streamID, URL, [](int errorCode) {
      if(errorCode == 0) {
          // Relaying successful
      } else {
          // Relaying failed, possibly due to network reasons causing the relaying request to fail
      }
  });

  // After publishing stream successfully, start relaying to CDN
  
  // Stream ID used when publishing
  std::string streamID = "STREAM_ID";
  // CDN address to be relayed, please fill in according to the actual URL, streamID is the stream name of publishing, can be customized
  std::string URL = "rtmp://publish_domain/entry_point/streamID";
  
  engine->addPublishCdnUrl(streamID, URL, [](int errorCode) {
      if(errorCode == 0) {
          // Relaying successful
      } else {
          // Relaying failed, possibly due to network reasons causing the relaying request to fail
      }
  });

(Optional) Listen to CDN Callback Status Notifications

Developers can register onPublisherRelayCDNStateUpdate to get callbacks for adding/deleting relay to CDN URL status. After ZEGO RTC server relays the audio/video stream to CDN, if the CDN relay status changes, such as relay stopping or relay retry, this callback will be received.

• Call example:

  class MyEventHandler:public IZegoEventHandler{
  public:
      void onPublisherRelayCDNStateUpdate(const std::string& /*streamID*/, const std::vector<ZegoStreamRelayCDNInfo>& /*streamInfoList*/) {
          // After calling the dynamic relay interface successfully, when the CDN connection status changes, such as network interruption causing relay abnormalities, etc., the SDK will notify through this callback while retrying relaying
          // Please note, do not call any SDK interfaces in the SDK callback thread, you need to manually switch to another thread, otherwise a deadlock will occur
      }
  };
  auto handler=std::make_shared<MyEventHandler>();
  engine->setEventHandler(handler);

  class MyEventHandler:public IZegoEventHandler{
  public:
      void onPublisherRelayCDNStateUpdate(const std::string& /*streamID*/, const std::vector<ZegoStreamRelayCDNInfo>& /*streamInfoList*/) {
          // After calling the dynamic relay interface successfully, when the CDN connection status changes, such as network interruption causing relay abnormalities, etc., the SDK will notify through this callback while retrying relaying
          // Please note, do not call any SDK interfaces in the SDK callback thread, you need to manually switch to another thread, otherwise a deadlock will occur
      }
  };
  auto handler=std::make_shared<MyEventHandler>();
  engine->setEventHandler(handler);

Stop Relaying

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

• Call example:

  // Before stopping publishing stream, stop relaying to CDN first
  
  // Stream ID used when publishing
  std::string streamID = "STREAM_ID";
  // CDN address to stop relaying, please fill in according to the actual URL, streamID is the stream name of publishing
  std::string URL = "rtmp://publish_domain/entry_point/streamID";
  
  engine->removePublishCdnUrl(streamID, URL, [](int errorCode) {
      if(errorCode == 0) {
          // Stop relaying successful
      } else {
          // Stop relaying failed, possibly due to network reasons causing the stop relaying request to fail
      }
  });

  // Before stopping publishing stream, stop relaying to CDN first
  
  // Stream ID used when publishing
  std::string streamID = "STREAM_ID";
  // CDN address to stop relaying, please fill in according to the actual URL, streamID is the stream name of publishing
  std::string URL = "rtmp://publish_domain/entry_point/streamID";
  
  engine->removePublishCdnUrl(streamID, URL, [](int errorCode) {
      if(errorCode == 0) {
          // Stop relaying successful
      } else {
          // Stop relaying failed, possibly due to network reasons causing the stop relaying request to fail
      }
  });

Direct Publishing to CDN

Start Direct Publishing to CDN

Before publishing stream, call the enablePublishDirectToCDN interface to push the audio/video stream directly to CDN.

ZegoCDNConfig config;
// URL needs to be filled in by the developer according to the actual situation, streamID is the stream name of publishing, can be customized
config.url = "rtmp://publish_domain/entry_point/streamID";
engine->enablePublishDirectToCDN(true, &config);
engine->startPublishingStream("STREAM_ID");

ZegoCDNConfig config;
// URL needs to be filled in by the developer according to the actual situation, streamID is the stream name of publishing, can be customized
config.url = "rtmp://publish_domain/entry_point/streamID";
engine->enablePublishDirectToCDN(true, &config);
engine->startPublishingStream("STREAM_ID");

Stop Direct Publishing to CDN

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

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

engine->stopPublishingStream();
ZegoCDNConfig cdnConfig;
engine->enablePublishDirectToCDN(false, &cdnConfig);

engine->stopPublishingStream();
ZegoCDNConfig cdnConfig;
engine->enablePublishDirectToCDN(false, &cdnConfig);

Audience Playing Stream

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

• After the audio/video stream is successfully relayed to CDN, when developers want users to play streams from CDN, they need to use the custom playing method of passing in the URL, and cannot play streams through the stream ID. For the operation steps of URL playing, please refer to "1 Configure Playing Parameters" and "2 Start Playing Stream" in Playing Stream by URL.