audio - Exoplayer Channel Panning

Question

I am trying to follow this post here: Setting an app to output ALL audio on a single channel to pan audio from the exoplayer left or right.

Code from MainActivity.java:

    StereoVolumeProcessor stereoVolumeProcessor = new StereoVolumeProcessor();
    stereoVolumeProcessor.setChannelMap(new int[]{0,1});
    stereoVolumeProcessor.setVolume(1, 0);

    AudioProcessor.AudioFormat inputAudioFormat = new AudioProcessor.AudioFormat(
            44100, 2, C.ENCODING_PCM_16BIT);
    try {
        stereoVolumeProcessor.configure(inputAudioFormat);
    } catch (AudioProcessor.UnhandledAudioFormatException e) {
        e.printStackTrace();
    }

    RenderersFactory factory = new DefaultRenderersFactory(context){
        @Override
        protected AudioProcessor[] buildAudioProcessors() {
            return new AudioProcessor[] {stereoVolumeProcessor};
        }
    };

    LoadControl loadControl = new DefaultLoadControl.Builder()
            .setBufferDurationsMs(
                    DefaultLoadControl.DEFAULT_MIN_BUFFER_MS,
                    DefaultLoadControl.DEFAULT_MAX_BUFFER_MS,
                    DefaultLoadControl.DEFAULT_BUFFER_FOR_PLAYBACK_MS,
                    DefaultLoadControl.DEFAULT_BUFFER_FOR_PLAYBACK_AFTER_REBUFFER_MS)
            .createDefaultLoadControl();

    SimpleExoPlayer testPlayer = ExoPlayerFactory.newSimpleInstance(context,factory, new DefaultTrackSelector(context), loadControl);
    dataSourceFactory = new DefaultDataSourceFactory(activity.getApplicationContext(),
            Util.getUserAgent(activity.getApplicationContext(), "TEST"));


    test_filepath = "asset:///test.mp3";
    test_file_uri = Uri.parse(test_filepath);
    testSource = new ProgressiveMediaSource.Factory(dataSourceFactory)
            .createMediaSource(test_file_uri);

    testPlayer.prepare(testSource);

Code from StereoVolumeProcessor.java:

public class StereoVolumeProcessor implements AudioProcessor {

private int channelCount;
private int sampleRateHz;
private int[] pendingOutputChannels;

private boolean active;
private int[] outputChannels;
private ByteBuffer buffer;
private ByteBuffer outputBuffer;
private boolean inputEnded;

private float[] volume;

private static final int LEFT_SPEAKER = 0;
private static final int RIGHT_SPEAKER = 1;

public StereoVolumeProcessor() {
    buffer = EMPTY_BUFFER;
    outputBuffer = EMPTY_BUFFER;
    channelCount = Format.NO_VALUE;
    sampleRateHz = Format.NO_VALUE;
}


public void setChannelMap(int[] outputChannels) {
    Log.d("audioProcessor", "setChannelMap called");
    pendingOutputChannels = outputChannels;
}

//@Override
public boolean configure(int sampleRateHz, int channelCount, @C.Encoding int encoding)
        throws AudioProcessor.UnhandledAudioFormatException {
    Log.d("audioProcessor", "configure called");

    if(volume == null){
        Log.d("audioProcessor", "volume null error called");
        throw new IllegalStateException("volume has not been set! Call setVolume(float left,float right)");
    }

    boolean outputChannelsChanged = !Arrays.equals(pendingOutputChannels, outputChannels);
    outputChannels = pendingOutputChannels;
    if (outputChannels == null) {
        active = false;
        return outputChannelsChanged;
    }
    if (encoding != C.ENCODING_PCM_16BIT) {
        //throw new AudioProcessor.UnhandledAudioFormatException(sampleRateHz, channelCount, encoding);
        Log.d("audioProcessor","encoding is not PCM 16_BIT");
    }

    if (!outputChannelsChanged && this.sampleRateHz == sampleRateHz
            && this.channelCount == channelCount) {
        Log.d("audioProcessor","outputchannels not changed ");
        return false;
    }
    this.sampleRateHz = sampleRateHz;
    this.channelCount = channelCount;

    active = true;
    return true;
    //return setInputFormat(sampleRateHz, channelCount, encoding);
}

@Override
public AudioFormat configure(AudioFormat inputAudioFormat) throws UnhandledAudioFormatException {
    Log.d("audioProcessor","overriden audioformat configure called");
    //return null;

    @Nullable int[] outputChannels = pendingOutputChannels;
    if (outputChannels == null) {
        return AudioFormat.NOT_SET;
    }

    if (inputAudioFormat.encoding != C.ENCODING_PCM_16BIT) {
        Log.d("audioprocessor","encoding not correct");
        throw new UnhandledAudioFormatException(inputAudioFormat);
    }

    boolean active = inputAudioFormat.channelCount != outputChannels.length;
    for (int i = 0; i < outputChannels.length; i++) {
        int channelIndex = outputChannels[i];
        if (channelIndex >= inputAudioFormat.channelCount) {
            throw new UnhandledAudioFormatException(inputAudioFormat);
        }
        active |= (channelIndex != i);
    }

    Log.d("audioprocessor", "overriden audioformat - encoding: " + inputAudioFormat.encoding + " channelCount: " + inputAudioFormat.channelCount + " samplerate: " + inputAudioFormat.sampleRate + " outputchannels.length: " + outputChannels.length);

    return active
            ? new AudioFormat(inputAudioFormat.sampleRate, outputChannels.length, C.ENCODING_PCM_16BIT)
            : AudioFormat.NOT_SET;
}

@Override
public boolean isActive() {
    return active;
}

//@Override
public int getOutputChannelCount() {
    Log.d("audioProcessor", "getOutputChannelCount called");
    return outputChannels == null ? channelCount : outputChannels.length;
}

//@Override
public int getOutputEncoding() {
    Log.d("audioProcessor", "getOutputEncoding called");
    return C.ENCODING_PCM_16BIT;
}

/**
 * Returns the sample rate of audio output by the processor, in hertz. The value may change as a
 * result of calling {@link #configure(int, int, int)} and is undefined if the instance is not
 * active.
 */
//@Override
public int getOutputSampleRateHz() {
    Log.d("audioProcessor", "getOutputSampleRateHz called");
    return sampleRateHz;
}

@Override
public void queueInput(ByteBuffer inputBuffer) {
    Log.d("audioProcessor", "queueInput called");
    int position = inputBuffer.position();
    int limit = inputBuffer.limit();
    int size = limit - position;

    if (buffer.capacity() < size) {
        buffer = ByteBuffer.allocateDirect(size).order(ByteOrder.nativeOrder());
    } else {
        buffer.clear();
    }

    if(isActive()){
        int ch = 0;
        for(int i = position;i<limit;i+=2){
            short sample = (short) (inputBuffer.getShort(i)* volume[ch++]);
            buffer.putShort(sample);
            ch%=channelCount;
        }
    }else{
        throw new IllegalStateException();
    }

    inputBuffer.position(limit);
    buffer.flip();
    outputBuffer = buffer;
}

@Override
public void queueEndOfStream() {
    Log.d("audioProcessor", "queueEndofStream called");
    inputEnded = true;
}

/**
 * Sets the volume of right and left channels/speakers
 * The values are between 0.0 and 1.0
 *
 * @param left
 * @param right
 */
public void setVolume(float left,float right){
    Log.d("audioProcessor", "setVolume called");
    volume = new float[]{left,right};
}

public float getLeftVolume(){
    Log.d("audioProcessor", "getleftvolume called");
    return volume[LEFT_SPEAKER];
}

public float getRightVolume(){
    Log.d("audioProcessor", "getrightvolume called");
    return volume[RIGHT_SPEAKER];
}

@Override
public ByteBuffer getOutput() {
    Log.d("audioProcessor", "getoutput called");
    ByteBuffer outputBuffer = this.outputBuffer;
    this.outputBuffer = EMPTY_BUFFER;
    return outputBuffer;
}

@SuppressWarnings("ReferenceEquality")
@Override
public boolean isEnded() {
    Log.d("audioProcessor", "isEnded called");
    return inputEnded && outputBuffer == EMPTY_BUFFER;
}

@Override
public void flush() {
    Log.d("audioProcessor", "flush called");
    outputBuffer = EMPTY_BUFFER;
    inputEnded = false;
}

@Override
public void reset() {
    Log.d("audioProcessor", "reset called");
    flush();
    buffer = EMPTY_BUFFER;
    channelCount = Format.NO_VALUE;
    sampleRateHz = Format.NO_VALUE;
    outputChannels = null;
    active = false;
}

}

I noticed that queueInput() is never getting called, and the panning is not working. Not sure what I'm doing wrong here.

question from:https://stackoverflow.com/questions/65894855/exoplayer-channel-panning

Answer 1

Waitting for answers