C#•2mo ago

Add sound to audio input

Hi! I have an api that takes an audio from some input, e.g. microphone, and passes it furher to some external device. How can I add some sounds, or modify the sound before its passed to audio port? I need to add some distortion to the audio, like e.g. phone talk with very pool connection. Unfortunately, I can't modify the api

6 Replies

Sossenbinder•2mo ago

Sounds like you'd want to use a library like NAudio and modify the recording ahead of sending it to the API

HiveMind•2mo ago

The api takes data automatically. I guess I need to just modify the sound that is passed to audio output port. I guess I can do it somehow in NAudio, but some hits would be really useful

Sossenbinder•2mo ago

So, I ain't a big audio guy, but I just tried around a bit with (in full transparency) AI-generated code

using (var reader = new AudioFileReader(inputFile))
using (var writer = new WaveFileWriter(outputFile, reader.WaveFormat))
{

    float[] buffer = new float[1024];
    int samplesRead;

    float cutoffFrequency = 2000f;
    float dropoutChance = 0.05f;
    float bitReductionFactor = 0.2f; 

    float previousOutput = 0f;

    while ((samplesRead = reader.Read(buffer, 0, buffer.Length)) > 0)
    {
        for (int i = 0; i < samplesRead; i++)
        {
            if (Random.Shared.NextDouble() < dropoutChance)
            {
                buffer[i] = 0;
            }
            else
            {
                buffer[i] = (float)(Math.Round(buffer[i] / bitReductionFactor) * bitReductionFactor);

                float currentSample = buffer[i];
                buffer[i] = previousOutput + (cutoffFrequency / reader.WaveFormat.SampleRate) * (currentSample - previousOutput);
                previousOutput = buffer[i];
            }

            buffer[i] *= (float)(0.9 + Random.Shared.NextDouble() * 0.2);
        }

        writer.WriteSamples(buffer, 0, samplesRead);
    }
}

using (var reader = new AudioFileReader(inputFile))
using (var writer = new WaveFileWriter(outputFile, reader.WaveFormat))
{

    float[] buffer = new float[1024];
    int samplesRead;

    float cutoffFrequency = 2000f;
    float dropoutChance = 0.05f;
    float bitReductionFactor = 0.2f; 

    float previousOutput = 0f;

    while ((samplesRead = reader.Read(buffer, 0, buffer.Length)) > 0)
    {
        for (int i = 0; i < samplesRead; i++)
        {
            if (Random.Shared.NextDouble() < dropoutChance)
            {
                buffer[i] = 0;
            }
            else
            {
                buffer[i] = (float)(Math.Round(buffer[i] / bitReductionFactor) * bitReductionFactor);

                float currentSample = buffer[i];
                buffer[i] = previousOutput + (cutoffFrequency / reader.WaveFormat.SampleRate) * (currentSample - previousOutput);
                previousOutput = buffer[i];
            }

            buffer[i] *= (float)(0.9 + Random.Shared.NextDouble() * 0.2);
        }

        writer.WriteSamples(buffer, 0, samplesRead);
    }
}

Sossenbinder•2mo ago

Air_conditioning.wav

Sossenbinder•2mo ago

Air_conditioning_out...

Sossenbinder•2mo ago

This is the result So it seems like you can definitely get somewhere pretty quickly

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Add sound to audio input