C# - NAudio - How to change sample rate on a float[] while reading it? - naudio

Question

I'm coding my first audio application, and I'm struggling for hours on trying to change samplerate of a cached sound.
I'm using NAudio and I was able to change the Volume, tweaking the Read() method of my ISampleProvider.
Here is the CachedSound Class :
public class CachedSound
{
public float[] AudioData { get; private set; }
public WaveFormat WaveFormat { get; set; }
public CachedSound(string audioFileName)
{
using (var audioFileReader = new AudioFileReader(audioFileName))
{
WaveFormat = audioFileReader.WaveFormat;
var wholeFile = new List<float>((int)(audioFileReader.Length / 4));
var readBuffer = new float[audioFileReader.WaveFormat.SampleRate * audioFileReader.WaveFormat.Channels];
int samplesRead;
while ((samplesRead = audioFileReader.Read(readBuffer, 0, readBuffer.Length)) > 0)
{
wholeFile.AddRange(readBuffer.Take(samplesRead));
}
AudioData = wholeFile.ToArray();
}
}
}
And here is the CachedSoundSampleProvider class :
using NAudio.Wave;
using System;
public delegate void PlaybackEndedHandler();
public class CachedSoundSampleProvider : ISampleProvider
{
public event PlaybackEndedHandler PlaybackEnded;
private CachedSound cachedSound;
private long _position;
public long Position {
get { return _position; }
set { _position = value; }
}
private float _volume;
public float Volume {
get { return _volume; }
set { _volume = value; }
}
private float _pitchMultiplicator;
public float PitchMultiplicator
{
get { return _pitchMultiplicator; }
set { _pitchMultiplicator = value; }
}
public WaveFormat OriginalWaveFormat { get; set; }
public WaveFormat WaveFormat {
get { return cachedSound.WaveFormat; }
}
//Constructeur
public CachedSoundSampleProvider(CachedSound _cachedSound)
{
cachedSound = _cachedSound;
OriginalWaveFormat = WaveFormat;
}
public int Read(float[] destBuffer, int offset, int numBytes)
{
long availableSamples = cachedSound.AudioData.Length - Position;
long samplesToCopy = Math.Min(availableSamples, numBytes);
//Changing original audio data samplerate
//Double speed to check if working
cachedSound.WaveFormat = new WaveFormat(cachedSound.WaveFormat.SampleRate*2, cachedSound.WaveFormat.Channels);
Array.Copy(cachedSound.AudioData, Position, destBuffer, offset, samplesToCopy);
//Changing Volume
for (int i = 0; i < destBuffer.Length; ++i)
destBuffer[i] *= (Volume > -40) ? (float)Math.Pow(10.0f, Volume * 0.05f) : 0;
Position += samplesToCopy;
if (availableSamples == 0) PlaybackEnded();
return (int)samplesToCopy;
}
}
I don't know how I can achieve this yet.
My goal is simple, I want to be able to tweak sample rate at realtime.
I read it's impossible to change it on the ISampleProvider interface.
That's why I tried to change it on the original audioData.
Thanks in advance for your help ! :)