Introduction

Before reading this article, you need to undersand two concepts: audio source and audio sink. Audio source is where audio frames come from, such as a microphone and a recorder. Audio sink is where audio frames go, such as a speaker and a earpiece.

By default, the Agora SDK uses default audio and video modules for capturing and rendering in real-time communications.

However, the default modules might not meet your development requirements, such as in the following scenarios:

• Your app has its own audio or video module.
• You want to use a non-camera source, such as recorded screen data.
• You need to process the captured video with a pre-processing library for functions such as image enhancement.
• You need flexible device resource allocation to avoid conflicts with other services.

This article tells you how to use the Agora Native SDK to customize the audio source and sink.

Implementation

Before customizing the audio source or sink, ensure that you implement the basic real-time communication functions in your project. For details, see Start a Call or Start Live Interactive Streaming.

Custom audio source

Refer to the following steps to customize the audio source in your project:

1. Call the setExternalAudioSource method to enable the external audio source before joining a channel.
2. Record and process the audio data on your own.
3. Send the audio data back to the SDK using the pushExternalAudioFrame method.

API call sequence

Refer to the following diagram to customize the audio source in your project.

Sample code

Refer to the following code to customize the audio source in your project.

// Enable the external audio source mode.
rtcEngine.setExternalAudioSource(
    true,      // Enable the external audio source.
    44100,     // Sampling rate. Set it as 8k, 16k, 32k, 44.1k, or 48kHz.
    1          // The number of external audio channels. The maximum value is 2.
);

// To continually push the enternal audio frame.
rtcEngine.pushExternalAudioFrame(
    data,             // The audio data in the format of byte[].
    timestamp         // The timestamp of the audio frame.
);

API Reference

• setExternalAudioSource
• pushExternalAudioFrame

Custom audio sink

Refer to the following steps to customize the audio sink in your project:

1. Call the setExternalAudioSink method to enable the external audio sink before joining a channel.
2. After you join the channel, call the pullPlaybackAudioFrame method to get the remote audio data.
3. Play the remote audio data on your own.

API call sequence

Refer to the following diagram to customize the audio sink in your project.

Sample code

Refer to the following code to customize the audio sink in your project.

// Notify the SDK that you want to use the external audio sink.
rtcEngine.setExternalAudioSink(
    true,      // Enable the external audio sink.
    44100,     // Set the audio sample rate as 8k, 16k, 32k, 44.1k or 48kHz.
    1          // Number of channels. The maximum number is 2.
);

// Pull the remote audio data for playback.
rtcEngine.pullPlaybackAudioFrame(
    data,             // The audio data in the format of byte[].
    lengthInByte      // Byte length in byte of the audio data.
);

API reference

• setExternalAudioSink
• pullPlaybackAudioFrame

Sample code

Agora provides an open-source Customer recoder demo project on GitHub. You can download it for source code reference.

Consideration

Customizing the audio source and sink requires you to manage audio data recording and playback on your own.

• When customizing the audio source, you need to record and process the audio data on your own.
• When customizing the audio sink, you need to process and play back the audio data on your own.