tencent cloud

Basics

This document describes the live playback feature of Live Flutter Plugin.

Live streaming overview

In live streaming, the video source is pushed by the host in real time. When the host stops pushing the source, the player will also stop playing the video. Because the live stream is played back in real time, no progress bar will be displayed in the player during the playback.

Supported protocols

Common live streaming protocols are as listed below. We recommend you use an FLV-based live streaming URL that starts with http and ends with .flv for LVB. For LEB, we recommend you use the WebRTC protocol. For more information, see LEB.

Protocol	Advantage	Disadvantage	Playback Latency
HLS	Mature, well adapted to high-concurrency scenarios	SDK integration is required	3–5 seconds
FLV	Mature, well adapted to high-concurrency scenarios	SDK integration is required.	2-3 seconds
RTMP	Relatively low latency	Poor performance in high-concurrency scenarios	1-3 seconds
WebRTC	Lowest latency	SDK integration is required	< 1 second

Note：

LVB and LEB are priced differently. For details, see LVB Billing Overview and LEB Billing Overview.

Notes

The SDK does not impose any restrictions on the sources of playback URLs, which means you can use it to play both Tencent Cloud and non-Tencent Cloud URLs. However, the player of the SDK supports only live streaming URLs in FLV, RTMP, HLS (M3U8), and WebRTC formats and VOD URLs in MP4, HLS (M3U8), and FLV formats.

Sample Code

Tencent Cloud offers an easy-to-understand API example project to help you quickly learn how to use different APIs.

Platform	GitHub Address
iOS	GitHub
Android	GitHub
Flutter	live_flutter_plugin

Getting Started

1. Set dependencies

Integrate live_flutter_plugin into your application as instructed in SDK Integration Guide.

dependencies:
 live_flutter_plugin: latest version number

2. Configure a license for the SDK

1. Get the license:

• If you have the required license, get the license URL and key in the CSS console.
  
• If you don't have the required license, apply for a license as instructed in New License and Renewal.

2. Before your application calls features of live_flutter_plugin, complete the following configuration:

   import 'package:live_flutter_plugin/v2_tx_live_premier.dart';
   /// Tencent Cloud license management page (https://console.tencentcloud.com/live/license)
   setupLicense() {
   // The license URL of the current application
   var LICENSEURL = "";
   // The license key of the current application
   var LICENSEURLKEY = "";
   V2TXLivePremier.setLicence(LICENSEURL, LICENSEURLKEY);
   }
   

Note：

The packageName/BundleId configured in the license must be the same as that of the application; otherwise, playback will fail.

3. Create the player

The V2TXLivePlayer module in the SDK offers live playback capabilities.

import 'package:live_flutter_plugin/v2_tx_live_player.dart';
/// Initialize `V2TXLivePlayer`
initPlayer() {
 _livePlayer = V2TXLivePlayer();
 _livePlayer.addListener(onPlayerObserver);
}

4. Render the view

In Flutter, you need to depend on v2_tx_live_video_widget to create a video rendering view for the player to display video images on.

import 'package:live_flutter_plugin/widget/v2_tx_live_video_widget.dart';
/// The video rendering view widget
Widget renderView() {
return V2TXLiveVideoWidget(
  onViewCreated: (viewId) async {
    // Set the video rendering view
    _livePlayer.setRenderViewID(_renderViewId);
  },
);
}

5. Start playback

/// Start pulling the stream
startPlay() async {
 // Generate the `url` (RTMP/TRTC/LEB)
 var url = ""
 // Start pulling the stream
 await _livePlayer?.startPlay(url);
}

• How do I get a valid stream push URL?
  Activate CSS. In the CSS console, go to Auxiliary Tools > Address Generator to generate a stream push URL. For more information, see Publishing/Playback URL.
  
• Why is V2TXLIVE_ERROR_INVALID_LICENSE returned?
  If the startPush API returns V2TXLIVE_ERROR_INVALID_LICENSE, it means your license verification failed. Please check your configuration against Step 2. Configure a license for the SDK.

6. Adjust the image

• setRenderFillMode: Fill or fit

  Value	Description
  V2TXLiveFillModeFill	Images are scaled to fill the entire screen, and the excess parts are cropped. There are no black bars in this mode, but images may not be displayed entirely.
  V2TXLiveFillModeFit	Images are scaled so that the long side of the video fits the screen. Neither side exceeds the screen after scaling. Images are centered, and there may be black bars visible.

• setRenderRotation: Clockwise rotation of video

  Value	Description
  V2TXLiveRotation0	No rotation
  V2TXLiveRotation90	Rotate 90 degrees clockwise
  V2TXLiveRotation180	Rotate 180 degrees
  V2TXLiveRotation270	Rotate 270 degrees clockwise

7. Pause playback

Technically speaking, you cannot pause a live playback. In this document, pausing live playback refers to freezing the video and disabling the audio. While the video is frozen, new video streams continue to be sent to the cloud. When you resume playback, it resumes playing the current latest stream. This is different from pausing and resuming playback in VOD, in which the player behaves the same way as it does when you pause and resume a local video file.

// Pause playback
_livePlayer.pauseAudio();
_livePlayer.pauseVideo();
// Resume playback
_livePlayer.resumeAudio();
_livePlayer.resumeVideo();

8. Stop playback

// Stop playback
_livePlayer.stopPlay();

Latency Control

The live playback feature of the SDK is not based on FFmpeg, but Tencent Cloud's proprietary playback engine, which is why the SDK offers better latency control than open-source players do. We provide three latency control modes, which can be used for live showrooms, game streaming, and hybrid scenarios.

• Comparison of control modes

  Mode	Stutter	Average Latency	Scenario	Remarks
  Speedy	Relatively high	2-3s	Live showroom	Has better latency control and is suitable for scenarios that require a low latency.
  Smooth	Low	>= 5s	Game streaming	Suitable for game live streaming scenarios with a high bitrate.
  Auto	Adapts to network conditions	2-8s	Hybrid	The better the network conditions at the audience end, the lower the latency.

• Code to integrate the three modes

  // Auto mode
  _txLivePlayer.setCacheParams(1, 5);
  // Speedy mode
  _txLivePlayer.setCacheParams(1, 1);
  // Smooth mode
  _txLivePlayer.setCacheParams(5, 5);
  // Start playback after configuration
  

Note：

For more information on stutter and latency control, see Video Stutter.

Listening for SDK Events

You can bind a V2TXLivePlayerObserver to V2TXLivePlayer. Then, all internal SDK status information, such as player status, playback volume level, reception of the first audio/video frame, statistical data, warnings, and errors, will be notified to you through corresponding callbacks.

Periodically triggered notification

• The onStatisticsUpdate notification is triggered once every 2 seconds to provide real-time feedback on the current player status. It can act as a dashboard to inform you of what is happening inside the SDK so you can better understand the current network conditions and video information.

  Parameter	Description
  appCpu	CPU usage (%) of the application
  systemCpu	CPU usage (%) of the system
  width	Video width
  height	Video height
  fps	Frame rate (fps)
  audioBitrate	Audio bitrate (Kbps)
  videoBitrate	Video bitrate (Kbps)

• onPlayoutVolumeUpdate is the callback for the player volume level. It will be returned only when you call enableVolumeEvaluation to enable the prompt for the player volume level. The callback interval is the same as that specified by the intervalMs parameter in enableVolumeEvaluation.

Event-triggered notifications

Other callbacks are triggered when specific events occur.