Im having problems with the reconstruction through two-channel filter bank when I use my audio files.

Following these steps: https://es.mathworks.com/help/dsp/examples/reconstruction-through-two-channel-filter-bank.html

With the default audio, all works fine. But when I use my own audio files (audioInput = dsp.AudioFileReader('random.mp3')), the hi and lo coefficients are 0. Any idea?

This is my code, for the analysis part:

audioInput = dsp.AudioFileReader('filename.mp3'); % read the audio file
N = 99; % filters order
[LPAnalysis, HPAnalysis, LPSynthsis, HPSynthesis] = firpr2chfb(N, 0.45);
analysisFilter = dsp.SubbandAnalysisFilter(LPAnalysis, HPAnalysis);                                                                                                                                                                                                       
while ~isDone(audioInput)
  input = audioInput();  % Load a frame of audio
  [hi, lo] = analysisFilter(input); 
end
end

Answer 1

[Rollin Baker]

Hi Christian,

The reason you are seeing zeros for your final result is because you are overwriting all previous values for 'hi' and 'lo' every time you go through the loop. This means that when the loop terminates, the values stored in 'hi' and 'lo' will only correspond to the last frame of the audio file. If the last frame of the file has no sound in it, then it makes sense that you would see the zeros.

To avoid this, you will want to keep an array that tracks all the high and low values, and add to it as you loop through each frame. I've included some code below so you can see ho this is done:

 audioInput = dsp.AudioFileReader('filename.mp3'); % read the audio file
 N = 99; % filters order
 [LPAnalysis, HPAnalysis, LPSynthsis, HPSynthesis] = firpr2chfb(N, 0.45);
 analysisFilter = dsp.SubbandAnalysisFilter(LPAnalysis, HPAnalysis);
 % Initialize hi and lo as empty cell arrays
 hi = {};
 lo = {};
 while ~isDone(audioInput)
     input = audioInput();  % Load a frame of audio
     [frameHi, frameLo] = analysisFilter(input);
     % Add the current frame's coefficients to the global array
     hi{end + 1} = frameHi; %#ok<SAGROW>
     lo{end + 1} = frameLo; %#ok<SAGROW> 
 end

After this code runs, 'hi' and 'lo' will be cell arrays, where each cell holds the values for a single frame.

I hope you find this helpful. Good luck on your project!

[Christian Segovia]

Thanks!