Using FFT in TarsosDSP library in android

Question

I'm just starting to use TarsosDSP for android and I can't figure out how to use FFT. Can anyone provide me with a sample? I just wanna read a file and get FFT output of it.

Answer 1

Try this code:

    new AndroidFFMPEGLocator(this);
    new Thread(new Runnable() {
        @Override
        public void run() {
            File externalStorage = Environment.getExternalStorageDirectory();
            File sourceFile = new File(externalStorage.getAbsolutePath() , "/440.mp3");

            final int bufferSize = 4096;
            final int fftSize = bufferSize / 2;
            final int sampleRate = 44100;

            AudioDispatcher audioDispatcher;
            audioDispatcher = AudioDispatcherFactory.fromPipe(sourceFile.getAbsolutePath(), sampleRate, bufferSize, 0);
            audioDispatcher.addAudioProcessor(new AudioProcessor() {

                FFT fft = new FFT(bufferSize);
                final float[] amplitudes = new float[fftSize];

                @Override
                public boolean process(AudioEvent audioEvent) {
                    float[] audioBuffer = audioEvent.getFloatBuffer();
                    fft.forwardTransform(audioBuffer);
                    fft.modulus(audioBuffer, amplitudes);

                    for (int i = 0; i < amplitudes.length; i++) {
                        Log.d(TAG, String.format("Amplitude at %3d Hz: %8.3f", (int) fft.binToHz(i, sampleRate) , amplitudes[i]));
                    }

                    return true;
                }

                @Override
                public void processingFinished() {

                }
            });
            audioDispatcher.run();
        }
    }).start();

It based on TarsosDSP Manual (page 12) and calculates and shows in log FFT for each bufferSize of 440.mp3 file (test 440Hz tone) on External storage (SD card). You should add TarsosDSP-Android-2.3.jar (or newer) from here to libs folder of your project (and add it as a library) and corresponding to your device ffmpeg library (armeabi-v7a_ffmpeg, armeabi-v7a-neon_ffmpeg or x86_ffmpeg) from here to assets folder of your project.

And don't forget add

<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />

to AndroidManifest.xml (and also give runtime permissions for targetSdkVersion higher then 21)

PS. You can give FFT for whole file if bufferSize will be equals to number of samples in source file (or bigger).