Questions

Hello.

I’m trying to modifying Audio Analyzer Example.

This is scenario.

1. Read wav file
2. Calculate FFT (for all sample data of wav file)
3. Display FFT result to FFT & Spectrogram chart.

The point is this : read all data at once and calulate FFT for dispaly in chart.

I already have FFT result with re[] and im[] type arrays.

1. When I setting up X,Y axis of FFT chart, following code applied.
   Q. x,y axis and value setup is correct?

               // prepare fft input (dataF is float type sample data of wav file)
               double[] re = new double[dataF.length];
               double[] im = new double[dataF.length];
               double[] mag = new double[dataF.length];
               for(int ii=0; ii<dataF.length; ii++) {
                   re[ii] = (double)dataF[ii];
                   im[ii] = 0.0d;
               }
   
               FFTf.transform(re, im);  // using Bluestein DFT algorithm.
   
               for(int nn=0; nn < re.length; nn++) {
                   mag[nn] = Math.sqrt(re[nn] * re[nn] + im[nn] * im[nn]);
                   if(nn <= 10 || re.length - 10 <= nn)
               }
   
               // setup fft and x,y values
               for(int l=0; l < re.length/20; l++) {
                   fftDS.append((1.0*l*sampleRate/re.length), Math.sqrt(re[l] * re[l] + im[l] * im[l]));
               }
   

2. When I setting up X,Y axis of Spectrogram chart, following code applied.
   Q. x,y axis and value setup is correct?

               fftCount = dataProvider.getAudioDataByteSize() / 4096;
               spectrogramDS = new UniformHeatmapDataSeries<>(Long.class, Long.class, Double.class, re.length/20, fftCount);
               fftOffsetValueCount = (re.length/20)*fftCount - (re.length/20);
               spectrogramValues = new DoubleValues((re.length/20)*fftCount);
               spectrogramValues.setSize((re.length/20)*fftCount);
   
               // update spectrogram chart data
               for(int jj=0; jj < fftCount; jj += 4096) {
                   double[] spectrogramItems = spectrogramValues.getItemsArray();
                   double[] fftItems = getFrom(mag, 4096, jj);
   
                   System.arraycopy(spectrogramItems, re.length/20, spectrogramItems, 0, fftOffsetValueCount);
                   System.arraycopy(fftItems, 0, spectrogramItems, fftOffsetValueCount, re.length/20);
   
                   spectrogramDS.updateZValues(spectrogramValues);
               }
   

FFT chart is working but Spectrogram is not.

Thank you for your help!