Use OnPlaybackAudioFrameBeforeMixing Event in Unity for Audio

Introduction 

In Unity applications utilizing Agora’s SDK, developers might encounter a scenario where the OnPlaybackAudioFrameBeforeMixing event does not trigger as expected. This event is crucial for applications that require processing individual user audio data, such as for lip-syncing purposes. This guide addresses how to properly configure your Unity project to ensure the OnPlaybackAudioFrameBeforeMixing event is called, allowing access to pre-mixed audio frames from each user in the channel.

Problem Statement

The OnPlaybackAudioFrameBeforeMixing event is not being called in the Unity example for processing audio raw data, despite successfully joining the channel and receiving audio through the OnPlaybackAudioFrame event. The requirement is to access individual user audio for advanced processing, like lip-syncing.

Solution Overview

To resolve this issue and ensure the OnPlaybackAudioFrameBeforeMixing event is triggered as expected, you must set the playback audio frame parameters before joining a channel. This involves specifying the desired sample rate and channel number for the audio frames you wish to receive.

Step-by-Step Guide

• Understanding the Required Parameters:
• SAMPLE_RATE: The sample rate of the audio frames you wish to receive. Common values include 8000, 16000, 32000, 44100, and 48000 Hz.
• CHANNEL: The number of audio channels. 1 for mono and 2 for stereo.
• Configuring Audio Frame Parameters: Before joining a channel, configure the playback audio frame parameters using the SetPlaybackAudioFrameBeforeMixingParameters method provided by Agora’s Unity SDK. This method allows the SDK to prepare for capturing individual user audio according to the specified parameters.
• Sample Code Implementation: Here is how you can set the playback audio frame parameters in your Unity script:
  

  using agora_gaming_rtc;
        public class YourClass : MonoBehaviour
        private const int SAMPLE_RATE = 48000; // Example sample rate
        private const int CHANNEL = 1; // Define channel number - Mono audio
        void Start()
        // Assuming you have initialized the RtcEngine instance
        IRtcEngine rtcEngine = IRtcEngine.QueryEngine();
        // Set the playback audio frame parameters before joining the channel
        rtcEngine.SetPlaybackAudioFrameBeforeMixingParameters(SAMPLE_RATE, CHANNEL);
        // Now you can join the channel
        rtcEngine.JoinChannel("yourChannelName", null, 0);

  Replace "yourChannelName" with the actual name of the channel you wish to join.

Additional Considerations

• Ensure you are using a version of Agora’s Unity SDK that supports the SetPlaybackAudioFrameBeforeMixingParameters method.
• Test the audio frame capture functionality across different devices to ensure compatibility and performance.