Single Stream Transcoding

Overview

Single stream transcoding refers to converting a single original stream into transcoded streams with different encoding formats and resolutions in the cloud. In scenarios such as live streaming, viewers can choose streams with different resolutions to watch based on network quality, terminal devices, etc., to ensure playback smoothness.

Application Scenarios

• When developers provide video streams with multiple resolutions for users to watch on demand, they need to convert the original stream into transcoded streams with different definitions. At this time, the single stream transcoding function can be used.
• When converting original video streams into different video encoding formats, the single stream transcoding function can be used. For example, when some devices cannot decode H.265 due to performance issues, they need to be transcoded to H.264.

Prerequisites

Before using the single stream transcoding function, please ensure:

• You have created a project in the ZEGOCLOUD Console and applied for a valid AppID and Server address. For details, please refer to Console - Project Information.
• You have integrated ZEGO Express SDK in your project and implemented basic audio/video Stream Publishing and Playing functions. For details, please refer to Quick Start - Integration and Quick Start - Implementation.
• You need to use L3 Stream Playing, CDN forwarding Stream Playing (pull by streamID), or RTC Stream Playing, and not use stream mixing capabilities.

Implementation Flow

The main flow of single stream transcoding is as follows:

1. Add transcoding template.
2. Create engine and log in to Room.
3. Pull transcoded streams on demand, choose the Stream Playing method as L3 Stream Playing, CDN forwarding Stream Playing (pull by streamID), or RTC as needed, and pass in the transcoding template ID to trigger transcoding.

1 Add Transcoding Template

Please contact ZEGO technical support to add a transcoding template and obtain the corresponding transcoding template ID.

Currently supported transcoding parameters are: template ID, resolution, bitrate, frame rate, and video encoding format.

2 Create Engine and Log in to Room

For specific flow, please refer to the Create Engine and Log in to Room sections of the "Implementing Video Call" document.

3 Pull Transcoded Stream

Configure the ZegoWebPlayOption > codecTemplateID property, fill in the transcoding template ID obtained in Step 1 Add transcoding configuration template, and start Stream Playing.

const stream = await zg.startPlayingStream(streamID, {
    codecTemplateID: 360, // Transcoding template ID
}

const stream = await zg.startPlayingStream(streamID, {
    codecTemplateID: 360, // Transcoding template ID
}

Enable Downgrade Transcoding Function (Optional)

Configure the ZegoWebPlayOption > transcodeOnDecodeFail property to true to enable the downgrade transcoding function. After enabling, normally pull the original stream directly. The SDK will use single stream transcoding to other video encoding when video decoding fails, but Stream Playing detection of video encoding availability will increase retry time.

const stream = await zg.startPlayingStream(streamID, {
    codecTemplateID: 360, // Transcoding template ID
// !mark
    transcodeOnDecodeFail: true
}

const stream = await zg.startPlayingStream(streamID, {
    codecTemplateID: 360, // Transcoding template ID
// !mark
    transcodeOnDecodeFail: true
}

FAQ