Publishing Multiple Streams Simultaneously

Feature Overview

The Express SDK provides the capability to publish multiple streams simultaneously. When the following situations occur in your business, it is recommended to use the SDK's multiple stream publishing feature:

• Game streamers publish camera footage on the main channel and screen capture footage on the second channel.
• Outdoor streamers publish front camera footage on the main channel and rear camera footage on the second channel.

Example Source Code Download

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

For related source code, please check files in the "/ZegoExpressExample/Examples/AdvancedStreaming/PublishingMultipleStreams" directory in the downloaded example source code.

Prerequisites

Before implementing the multiple stream publishing feature, 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 streaming functionality. For details, see Quick Start - Integration and Quick Start - Implementation Flow.

Usage Steps

1 Create ZegoExpressEngine Engine

Please refer to "Create Engine" in Quick Start - Implementation Flow.

ZegoEngineProfile *profile = [[ZegoEngineProfile alloc] init];
profile.appID = [KeyCenter appID];
profile.appSign = [KeyCenter appSign];
profile.scenario = ZegoScenarioDefault;
[ZegoExpressEngine createEngineWithProfile:profile eventHandler:self];

ZegoEngineProfile *profile = [[ZegoEngineProfile alloc] init];
profile.appID = [KeyCenter appID];
profile.appSign = [KeyCenter appSign];
profile.scenario = ZegoScenarioDefault;
[ZegoExpressEngine createEngineWithProfile:profile eventHandler:self];

2 (Optional) Set Custom Video Capture Configuration

ZegoCustomVideoCaptureConfig *captureConfig = [[ZegoCustomVideoCaptureConfig alloc] init];
// Select CVPixelBuffer type video frame data
captureConfig.bufferType = ZegoVideoBufferTypeCVPixelBuffer;

[[ZegoExpressEngine sharedEngine] enableCustomVideoCapture:YES config:captureConfig channel:ZegoPublishChannelAux];

ZegoCustomVideoCaptureConfig *captureConfig = [[ZegoCustomVideoCaptureConfig alloc] init];
// Select CVPixelBuffer type video frame data
captureConfig.bufferType = ZegoVideoBufferTypeCVPixelBuffer;

[[ZegoExpressEngine sharedEngine] enableCustomVideoCapture:YES config:captureConfig channel:ZegoPublishChannelAux];

3 (Optional) Set Auxiliary Publisher Custom Video Capture Callback

@interface ViewController () <ZegoEventHandler, ZegoCustomVideoCaptureHandler>

    ......

@end

@interface ViewController () <ZegoEventHandler, ZegoCustomVideoCaptureHandler>

    ......

@end

// Set self as the custom video capture callback object
[[ZegoExpressEngine sharedEngine] setCustomVideoCaptureHandler:self];

// Set self as the custom video capture callback object
[[ZegoExpressEngine sharedEngine] setCustomVideoCaptureHandler:self];

// Note: This callback is not on the main thread. If there are UI operations, please switch to the main thread yourself
- (void)onStart {

    // After receiving the callback, developers need to execute business logic related to starting capture, such as starting the camera, etc.

    // This example starts a self-implemented video capture device
    [self.captureDevice startCapture];
}

// Note: This callback is not on the main thread. If there are UI operations, please switch to the main thread yourself
- (void)onStop {

    // After receiving the callback, developers need to execute business logic related to stopping capture, such as stopping the camera, etc.

    // This example stops a self-implemented video capture device
    [self.captureDevice stopCapture];
}

// Note: This callback is not on the main thread. If there are UI operations, please switch to the main thread yourself
- (void)onStart {

    // After receiving the callback, developers need to execute business logic related to starting capture, such as starting the camera, etc.

    // This example starts a self-implemented video capture device
    [self.captureDevice startCapture];
}

// Note: This callback is not on the main thread. If there are UI operations, please switch to the main thread yourself
- (void)onStop {

    // After receiving the callback, developers need to execute business logic related to stopping capture, such as stopping the camera, etc.

    // This example stops a self-implemented video capture device
    [self.captureDevice stopCapture];
}

4 Call Auxiliary Publisher Methods to Implement Preview and Publishing

After logging in to the room, call the start preview interface startPreview or start publishing stream interface startPublishingStream to trigger the onStart of 3 Set Auxiliary Publisher Custom Video Capture Callback. When the onStart callback is triggered, developers can start capturing video frame data.

When stopping publishing stream stopPublishingStream and stopping preview stopPreview , the onStop callback of 3 Set Auxiliary Publisher Custom Video Capture Callback will be triggered. At this time, developers should stop capturing video data.

[self.engine startPreview:mainPreviewCanvas channel:ZegoPublishChannelAux];
[self.engine startPublishingStream:self.auxStreamID channel:ZegoPublishChannelAux];

[self.engine startPreview:mainPreviewCanvas channel:ZegoPublishChannelAux];
[self.engine startPublishingStream:self.auxStreamID channel:ZegoPublishChannelAux];

5 (Optional) Send Captured Video Frame Data to SDK

[self.engine sendCustomVideoCaptureTextureData:textureID size:size timeStamp:timeStamp channel:ZegoPublishChannelAux];

[self.engine sendCustomVideoCaptureTextureData:textureID size:size timeStamp:timeStamp channel:ZegoPublishChannelAux];

[self.engine sendCustomVideoCapturePixelBuffer:data timeStamp:timeStamp channel:ZegoPublishChannelAux];

[self.engine sendCustomVideoCapturePixelBuffer:data timeStamp:timeStamp channel:ZegoPublishChannelAux];

6 Set Non-Main Channel Publishing Event Callbacks

Call the auxiliary publisher's setEventHandler interface to set event callbacks for the auxiliary publisher to receive notifications such as "publishing state change callback", "publishing quality callback", "publishing first frame callback", etc.

[self.player setEventHandler:self];

- (void)onPublisherStateUpdate:(ZegoPublisherState)state errorCode:(int)errorCode extendedData:(nullable NSDictionary *)extendedData streamID:(NSString *)streamID{
    // Perform logic for corresponding publishing action results
        ...
};
- (void)onPublisherQualityUpdate:(ZegoPublishStreamQuality *)quality streamID:(NSString *)streamID{
    // Perform business logic such as displaying stream quality during publishing
        ...
};
- (void)onPublisherCapturedVideoFirstFrame:(ZegoPublishChannel)channel{
    // Notification that SDK received video data for the first time
        ...
};
- (void)onPublisherVideoSizeChanged:(CGSize)size channel:(ZegoPublishChannel)channel{
    // Developers can perform logic such as removing UI mask spaces for displaying video in this callback
};
- (void)onPublisherRelayCDNStateUpdate:(NSArray<ZegoStreamRelayCDNInfo *> *)infoList streamID:(NSString *)streamID{
    // Notification that stream is relayed to CDN
};

// Other overridden callbacks
...

});

[self.player setEventHandler:self];

- (void)onPublisherStateUpdate:(ZegoPublisherState)state errorCode:(int)errorCode extendedData:(nullable NSDictionary *)extendedData streamID:(NSString *)streamID{
    // Perform logic for corresponding publishing action results
        ...
};
- (void)onPublisherQualityUpdate:(ZegoPublishStreamQuality *)quality streamID:(NSString *)streamID{
    // Perform business logic such as displaying stream quality during publishing
        ...
};
- (void)onPublisherCapturedVideoFirstFrame:(ZegoPublishChannel)channel{
    // Notification that SDK received video data for the first time
        ...
};
- (void)onPublisherVideoSizeChanged:(CGSize)size channel:(ZegoPublishChannel)channel{
    // Developers can perform logic such as removing UI mask spaces for displaying video in this callback
};
- (void)onPublisherRelayCDNStateUpdate:(NSArray<ZegoStreamRelayCDNInfo *> *)infoList streamID:(NSString *)streamID{
    // Notification that stream is relayed to CDN
};

// Other overridden callbacks
...

});

FAQ

1. When will onStart be called back?

   When custom video capture is enabled, it will be triggered when the SDK starts publishing stream startPublishingStream or starts preview startPreview .

2. Does it support publishing more than 4 streams simultaneously?

   To work with the real-time signaling feature, the SDK currently supports a maximum of 4 publishing channels by default, but before version 2.14.0, the default maximum number of publishing channels is 2. If you need to support more publishing channels, please contact ZEGOCLOUD Technical Support for special packaging.