Custom audio playback

1. Start audio playback in external mode

When calling startAudioPlayer, set isExternal=true to disable the SDK's internal audio rendering device. The application layer is then responsible for playing back the audio.

AoqClientEngine.AoqAudioPlaybackConfig config = new AoqClientEngine.AoqAudioPlaybackConfig();
config.isExternal = true;  // Disable SDK internal playback; application layer renders audio
config.channel = 1;        // Number of channels
engine.startAudioPlayer(config);

Parameters:

2. Set the audio frame callback listener

Call setAudioFrameObserver to register the audio frame data callback listener. Implement the onPlaybackAudioFrame callback method to receive the playback PCM data.

engine.setAudioFrameObserver(new AoqClientListener.AoqAudioFrameListener() {
    @Override
    public void onPlaybackAudioFrame(@NonNull AoqClientEngine.AoqAudioFrameData frame) {
        // Process the received playback audio data here
        // frame.dataPtr: PCM data
        // frame.numOfSamples: number of samples
        // frame.numOfChannels: number of channels
        // frame.samplesPerSec: sample rate
        // frame.bytesPerSample: bytes per sample
        playPcmData(frame);
    }
});

3. Enable playback data callbacks

Call enableAudioFrameObserver to enable audio frame callbacks at the playback position. Specify the data source as AoqAudioSourcePlayback.

AoqClientEngine.AoqAudioObserverConfig observerConfig = new AoqClientEngine.AoqAudioObserverConfig();
observerConfig.sampleRate = 48000;  // Callback audio sample rate
observerConfig.channels = 1;       // Callback audio channel count
observerConfig.mode = AoqClientEngine.AoqAudioObserverMode.AoqAudioObserverModeReadOnly; // Read-only mode

engine.enableAudioFrameObserver(
    true,  // Enable callbacks
    AoqClientEngine.AoqAudioSource.AoqAudioSourcePlayback,  // Playback data source
    observerConfig
);

Parameters:

4. Implement custom audio rendering

When PCM data arrives in the onPlaybackAudioFrame callback, the application layer handles rendering and playback. Common approaches include:

• Android AudioTrack: Write the PCM data to the system audio device using AudioTrack.

• AI speech recognition: Pass the PCM data to an ASR engine for speech recognition.

• Audio effects: Apply audio effects to the PCM data before playback.

• File storage: Save the received audio data to a local file.

// Example: Playback using Android AudioTrack
private AudioTrack mAudioTrack;
private volatile boolean mPlayRunning = false;

private void initAudioTrack(int sampleRate, int channels) {
    int channelConfig = (channels == 2)
        ? AudioFormat.CHANNEL_OUT_STEREO
        : AudioFormat.CHANNEL_OUT_MONO;
    int bufferSize = AudioTrack.getMinBufferSize(
        sampleRate, channelConfig, AudioFormat.ENCODING_PCM_16BIT);

    mAudioTrack = new AudioTrack(
        AudioManager.STREAM_VOICE_CALL,
        sampleRate,
        channelConfig,
        AudioFormat.ENCODING_PCM_16BIT,
        bufferSize,
        AudioTrack.MODE_STREAM);
    mAudioTrack.play();
    mPlayRunning = true;
}

private void playPcmData(AoqClientEngine.AoqAudioFrameData frame) {
    if (!mPlayRunning || mAudioTrack == null) {
        return;
    }
    if (frame.dataPtr != null && frame.dataSize > 0) {
        mAudioTrack.write(frame.dataPtr, 0, frame.dataSize);
    }
}

Important notes:

• The onPlaybackAudioFrame callback fires on an SDK internal thread. The frame.dataPtr is only valid during the callback. If you need to use the data asynchronously, copy it first.

• AudioTrack.write is a blocking operation. Writing directly inside the callback is fine because the SDK delivers callbacks at a controlled rate.

• Maintain the mPlayRunning flag so you can stop processing when the engine exits or playback stops.

5. Stop custom playback

When custom playback is no longer needed, disable the audio frame callback first, then stop the playback device and release the AudioTrack resources.

// 1. Disable audio frame callbacks at the playback position
AoqClientEngine.AoqAudioObserverConfig observerConfig = new AoqClientEngine.AoqAudioObserverConfig();
engine.enableAudioFrameObserver(
    false,  // Disable callbacks
    AoqClientEngine.AoqAudioSource.AoqAudioSourcePlayback,
    observerConfig
);

// 2. Remove the audio frame callback listener
engine.setAudioFrameObserver(null);

// 3. Stop SDK audio playback
engine.stopAudioPlayer();

// 4. Release AudioTrack resources
mPlayRunning = false;
if (mAudioTrack != null) {
    mAudioTrack.stop();
    mAudioTrack.release();
    mAudioTrack = null;
}