How to Mix 2 wav files together?

Question

I'm trying to record an input and merge it together with a song (not concatenate). I have a guitar that i recorded while listening to a song and I want to put the guitar on the song (like audcaity). Is there any way for doing it? If its not possible on real time mixing - is it possible to merge them after i recorded? Like after I recorded the guitar and now its a wav file and i want to mix 2 wav files together. Thats the input device:

 private void Capture()
    {
        input = new WasapiCapture((MMDevice)inputCombo.SelectedItem);
        bufferedWaveProvider = new BufferedWaveProvider(input.WaveFormat);
        input.DataAvailable += WaveInOnDataAvailable;
        input.StartRecording();
        write = new WaveFileWriter(System.IO.Path.GetTempFileName(), input.WaveFormat);
    }

 private void WaveInOnDataAvailable(object sender, WaveInEventArgs e)
    {
        bufferedWaveProvider.AddSamples(e.Buffer, 0, e.BytesRecorded);
        write.Write(e.Buffer, 0, e.BytesRecorded);
        write.Flush();
    }

Instead of writing it into a blank file i want to write it into a wav file thats already exists and not override it. Is it maybe possible with the MixingSampleProvider?

Answer 1

To mix multiple ISampleProvider sources using a MixingSampleProvider, you can do the following:

Here SignalGenerator has a Gain property which allows to specify how loud it should be in the mix.

using System;
using NAudio.Wave;
using NAudio.Wave.SampleProviders;

namespace ConsoleApplication1
{
    internal class Program
    {
        private static void Main(string[] args)
        {
            ISampleProvider provider1 = new SignalGenerator
            {
                Frequency = 1000.0f,
                Gain = 0.5f
            };

            ISampleProvider provider2 = new SignalGenerator
            {
                Frequency = 1250.0f,
                Gain = 0.5f
            };

            var takeDuration1 = TimeSpan.FromSeconds(5); // otherwise it would emit indefinitely
            var takeDuration2 = TimeSpan.FromSeconds(10);

            var sources = new[]
            {
                provider1.Take(takeDuration1),
                provider2.Take(takeDuration2)
            };

            var mixingSampleProvider = new MixingSampleProvider(sources);

            var waveProvider = mixingSampleProvider.ToWaveProvider();

            WaveFileWriter.CreateWaveFile("test.wav", waveProvider);
        }
    }
}