CODEWITHSUNDEEP
c#audiosignal-processingsound-recognitionmusic-notation
Norman Pratama
Norman Pratama

Reputation: 67

how to split wave signal into frames

I'm working a project about chord recognition. I'm using someone's journal as a reference but I still have little grasp in field of DSP. In her reference, first thing is I need to split the signal from wav file into number of frames. In my case, I need to split into 65 ms each frame, with 2866 sample per frame.

I have searched how to split signal into frames but I don't find them clear enough for me to understand. So far these are some of my codes in WavProcessing class:

 public void SetFileName(String fileNameWithPath) //called first in the form, to get the FileStream
    {
        _fileNameWithPath = fileNameWithPath;
        strm = File.OpenRead(_fileNameWithPath);

    }
 public double getLengthTime(uint wavSize, uint sampleRate, int bitRate, int channels)  
    {
        wavTimeLength = ((strm.Length - 44) / (sampleRate * (bitRate / 8))) / channels;
        return wavTimeLength;
    }

public int getNumberOfFrames() //return number of frames, I just divided total length time with interval time between frames. (in my case, 3000ms / 65 ms = 46 frames)
    { 
        numOfFrames = (int) (wavTimeLength * 1000 / _sampleFrameTime);
        return numOfFrames; 
    }

 public int getSamplePerFrame(UInt32 sampleRate, int sampleFrameTime) // return the sample per frame value (in my case, it's 2866)
    {
        _sampleRate = sampleRate;
        _sampleFrameTime = sampleFrameTime;

        sFr = (int)(sampleRate * (sampleFrameTime / 1000.0 ));

        return sFr; 
    }

I just still don't get the idea how to split the signal into 65 ms per frame in C#. Do I need to split the FileStream and break them into frames and save them into array? Or anything else?

Upvotes: 0

Views: 2273

Answers (1)

Mark Heath
Mark Heath

Reputation: 49482

with NAudio you would do it like this:

using (var reader = new AudioFileReader("myfile.wav"))
{
    float[] sampleBuffer = new float[2866];
    int samplesRead = reader.Read(sampleBuffer, 0, sampleBuffer.Length);
}

As others have commented, the number of samples you read ought to be a power of 2 if you plan to pass it into an FFT. Also, if the file is stereo, you will have left and right samples interleaved, so your FFT will need to be able to cope with this.

Upvotes: 1

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