Tutorial: 41-advanced-small-stream-auto-switcher

Function Introduction

This article mainly introduces how to use the SmallStreamAutoSwitcher plugin to enable automatic switching between large and small streams. This plugin is typically used in bandwidth-limited scenarios, where if bandwidth cannot meet the requirements for large streams causing stuttering, it automatically switches to small streams, which reduces resolution but ensures smoothness.

Prerequisites

• TRTC Web SDK version >= 5.11.0

Implementation Process

Import and Register Plugin

import SmallStreamAutoSwitcher from 'trtc-sdk-v5/plugins/small-stream-auto-switcher';
const trtc = TRTC.create({ plugins: [SmallStreamAutoSwitcher] });

Plugin Start

The default switching strategy is:

• When network delay exceeds 200ms or packet loss rate exceeds 20% for 10 consecutive seconds, and frame rate fluctuates significantly, switch to small stream
• When network delay is below 100ms and packet loss rate is below 10% for 20 consecutive seconds, and frame rate returns to normal, switch back to large stream
• Only allow automatic switching to small stream 2 times, after exceeding 2 times, no longer automatically switch to small stream

trtc.startPlugin('SmallStreamAutoSwitcher');

Plugin Stop

trtc.stopPlugin('SmallStreamAutoSwitcher');

Advanced Usage

You can customize parameters to adjust the plugin's strategy, for example:

Only allow automatic switching to small stream 1 time, and do not switch back to large stream after switching.

trtc.startPlugin('SmallStreamAutoSwitcher', {
  maxAutoSwitchToSmallCount: 1,
});

Below are explanations for all parameters. If not passed, default strategy will be used.

trtc.startPlugin('SmallStreamAutoSwitcher', {
  rttPoorLimit: 200, // Delay threshold, unit: ms, when delay exceeds this value, triggers condition to switch to small stream, default 200
  lossPoorLimit: 20, // Packet loss rate threshold, unit: %, when packet loss rate exceeds this value, triggers condition to switch to small stream, default 20
  poorDuration: 10 * 1000, // Duration threshold for poor network conditions, unit: ms, when delay or packet loss rate continuously exceeds threshold for this duration, start checking whether to switch to small stream, default 10000 (10 seconds)
  rttGoodLimit: 100, // Good delay threshold, unit: ms, when delay is below this value, triggers condition to switch to large stream, default 100
  lossGoodLimit: 10, // Good packet loss rate threshold, unit: %, when packet loss rate is below this value, triggers condition to switch to large stream, default 10
  goodDuration: 20 * 1000, // Duration threshold for good network conditions, unit: ms, when delay and packet loss rate are continuously below threshold for this duration, start checking whether to switch to large stream, default 20000 (20 seconds)
  sleepTime: 30 * 1000, // Sleep time after switching, unit: ms, no automatic switching will occur during this time, default 30000 (30 seconds)
  maxAutoSwitchToSmallCount: 2, // Maximum number of automatic switches to small stream per user, after exceeding this count, no longer automatically switch to small stream, default 2
});

Parameter Description

Switching Logic Description

Conditions for Switching to Small Stream

1. Network conditions: Delay continuously exceeds rttPoorLimit for poorCount times, or packet loss rate continuously exceeds lossPoorLimit for poorCount times
2. Frame rate conditions: Large stream frame rate fluctuates significantly (difference between maximum and minimum frame rate exceeds 1/3 of maximum frame rate)
3. Limiting conditions: User is currently subscribed to large stream, automatic switch count has not reached maxAutoSwitchToSmallCount limit, and not in sleep period

Conditions for Switching to Large Stream

1. Network conditions: Delay is continuously below rttGoodLimit for goodCount times, and packet loss rate is continuously below lossGoodLimit for goodCount times
2. Frame rate conditions: Small stream frame rate is stable (difference between maximum and minimum frame rate does not exceed 1/3 of maximum frame rate)
3. Limiting conditions: User is currently subscribed to small stream, and the user has only switched to small stream once, and not in sleep period

Note:

• Detection frequency is once every 2 seconds
• The statistical window size for network quality and frame rate data automatically adapts to the maximum value of poorDuration and goodDuration
• After each switch, it enters a sleep period of sleepTime duration, during which automatic switching will not be triggered again
• Only users who have automatically switched to small stream once are allowed to switch back to large stream, users who have switched twice will remain in small stream state