BufferSize Null Pointer Expectation Issue on new Mac Pro 2018

[cyrus-education]

When trying to record audio through microphone on new MacPro 2018, there will return the "null pointer expectation", it looks that the microphone is denied, any solutions? Thanks.

[matt0rtega]

Might have to do with the new permissions settings for audio in Mojave.

[ddf]

Yes, I'd assume it's a permission thing as well. Unfortunately, I don't have a Mac that can run Mojave, so I'm unable to investigate this.

[ddf]

Even without my being able to reproduce the issue, if you could provide a callstack of where the exception comes from, it might be possible to deal with the null pointer better. If a working AudioInput can't be created, then getLineIn will return null. This is the expected behavior and it is the caller's responsibility to ensure they check for null before using the returned AudioInput. However, if the null pointer exception is happening inside of the getLineIn call, I'd want to address that.

[matt0rtega]

I finally figured this out but posted in the Processing Discourse. The issue was that the RecordAudioInput example would no longer run, but running it with the getLineIn(Minim.MONO) argument got it working. Not sure why the change with the newer MacBook Pro or OS, but if others are experiencing this, might be worth updating the example.

` /**

• This sketch demonstrates how to an AudioRecorder to record audio to disk.
• To use this sketch you need to have something plugged into the line-in on your computer,
• or else be working on a laptop with an active built-in microphone.
• Press 'r' to toggle recording on and off and the press 's' to save to disk.
• The recorded file will be placed in the sketch folder of the sketch.
• For more information about Minim and additional features,
• visit http://code.compartmental.net/minim/ */

import ddf.minim.*;

Minim minim; AudioInput in; AudioRecorder recorder;

void setup() { size(512, 200, P3D);

minim = new Minim(this);

in = minim.getLineIn(Minim.MONO); // create a recorder that will record from the input to the filename specified // the file will be located in the sketch's root folder. recorder = minim.createRecorder(in, "myrecording.wav");

textFont(createFont("Arial", 12)); }

void draw() { background(0); stroke(255); // draw the waveforms // the values returned by left.get() and right.get() will be between -1 and 1, // so we need to scale them up to see the waveform for(int i = 0; i < in.bufferSize() - 1; i++) { line(i, 50 + in.left.get(i)50, i+1, 50 + in.left.get(i+1)50); line(i, 150 + in.right.get(i)50, i+1, 150 + in.right.get(i+1)50); }

if ( recorder.isRecording() ) { text("Currently recording...", 5, 15); } else { text("Not recording.", 5, 15); } }

void keyReleased() { if ( key == 'r' ) { // to indicate that you want to start or stop capturing audio data, you must call // beginRecord() and endRecord() on the AudioRecorder object. You can start and stop // as many times as you like, the audio data will be appended to the end of the buffer // (in the case of buffered recording) or to the end of the file (in the case of streamed recording). if ( recorder.isRecording() ) { recorder.endRecord(); } else { recorder.beginRecord(); } } if ( key == 's' ) { // we've filled the file out buffer, // now write it to the file we specified in createRecorder // in the case of buffered recording, if the buffer is large, // this will appear to freeze the sketch for sometime // in the case of streamed recording, // it will not freeze as the data is already in the file and all that is being done // is closing the file. // the method returns the recorded audio as an AudioRecording, // see the example AudioRecorder >> RecordAndPlayback for more about that recorder.save(); println("Done saving."); } } `

[ddf]

Ah, thanks for the info. I will try this out on my Macbook and see if I get a similar result. The version of getLineIn requests a STEREO input, but a Macbook microphone is definitely a MONO input. Maybe macOS was less picky about that before.

[ddf]

Could you do me a favor and open up your Audio MIDI Setup and have a look at the Audio Devices window? I'm curious to see if your "Built-in Input" or similar is set to 1 channel or 2. Mine is set to 2 channels (see below) and doesn't have any settings for 1 channel. So I am able to run the sketch as written without any problems. It also runs just fine if use getLineIn(Minim.MONO).

[matt0rtega]

I think you've found it. Only one channel appearing I guess in the new OS. Not sure if this is something I can change.

[ddf]

Ok, yep, then I think your initial suggestion to change the example so it gets a MONO input is the best approach. I should also probably add a comment to the effect that STEREO inputs are supported, but availability will depend on the computer's audio input configuration. And should probably also check for null in case someone runs the sketch on a machine that has all audio inputs disabled...