Unity3D: script to save an AudioClip as a .wav file.

SavWav.cs

//	Copyright (c) 2012 Calvin Rien
//        http://the.darktable.com
//
//	This software is provided 'as-is', without any express or implied warranty. In
//	no event will the authors be held liable for any damages arising from the use
//	of this software.
//
//	Permission is granted to anyone to use this software for any purpose,
//	including commercial applications, and to alter it and redistribute it freely,
//	subject to the following restrictions:
//
//	1. The origin of this software must not be misrepresented; you must not claim
//	that you wrote the original software. If you use this software in a product,
//	an acknowledgment in the product documentation would be appreciated but is not
//	required.
//
//	2. Altered source versions must be plainly marked as such, and must not be
//	misrepresented as being the original software.
//
//	3. This notice may not be removed or altered from any source distribution.
//
//  =============================================================================
//
//  derived from Gregorio Zanon's script
//  http://forum.unity3d.com/threads/119295-Writing-AudioListener.GetOutputData-to-wav-problem?p=806734&viewfull=1#post806734

using System;
using System.IO;
using UnityEngine;
using System.Collections.Generic;

public static class SavWav {

	const int HEADER_SIZE = 44;

	public static bool Save(string filename, AudioClip clip) {
		if (!filename.ToLower().EndsWith(".wav")) {
			filename += ".wav";
		}

		var filepath = Path.Combine(Application.persistentDataPath, filename);

		Debug.Log(filepath);

		// Make sure directory exists if user is saving to sub dir.
		Directory.CreateDirectory(Path.GetDirectoryName(filepath));

		using (var fileStream = CreateEmpty(filepath)) {

			ConvertAndWrite(fileStream, clip);

			WriteHeader(fileStream, clip);
		}

		return true; // TODO: return false if there's a failure saving the file
	}

	public static AudioClip TrimSilence(AudioClip clip, float min) {
		var samples = new float[clip.samples];

		clip.GetData(samples, 0);

		return TrimSilence(new List<float>(samples), min, clip.channels, clip.frequency);
	}

	public static AudioClip TrimSilence(List<float> samples, float min, int channels, int hz) {
		return TrimSilence(samples, min, channels, hz, false, false);
	}

	public static AudioClip TrimSilence(List<float> samples, float min, int channels, int hz, bool _3D, bool stream) {
		int i;

		for (i=0; i<samples.Count; i++) {
			if (Mathf.Abs(samples[i]) > min) {
				break;
			}
		}

		samples.RemoveRange(0, i);

		for (i=samples.Count - 1; i>0; i--) {
			if (Mathf.Abs(samples[i]) > min) {
				break;
			}
		}

		samples.RemoveRange(i, samples.Count - i);

		var clip = AudioClip.Create("TempClip", samples.Count, channels, hz, _3D, stream);

		clip.SetData(samples.ToArray(), 0);

		return clip;
	}

	static FileStream CreateEmpty(string filepath) {
		var fileStream = new FileStream(filepath, FileMode.Create);
	    byte emptyByte = new byte();

	    for(int i = 0; i < HEADER_SIZE; i++) //preparing the header
	    {
	        fileStream.WriteByte(emptyByte);
	    }

		return fileStream;
	}

	static void ConvertAndWrite(FileStream fileStream, AudioClip clip) {

		var samples = new float[clip.samples];

		clip.GetData(samples, 0);

		Int16[] intData = new Int16[samples.Length];
		//converting in 2 float[] steps to Int16[], //then Int16[] to Byte[]

		Byte[] bytesData = new Byte[samples.Length * 2];
		//bytesData array is twice the size of
		//dataSource array because a float converted in Int16 is 2 bytes.

		int rescaleFactor = 32767; //to convert float to Int16

		for (int i = 0; i<samples.Length; i++) {
			intData[i] = (short) (samples[i] * rescaleFactor);
			Byte[] byteArr = new Byte[2];
			byteArr = BitConverter.GetBytes(intData[i]);
			byteArr.CopyTo(bytesData, i * 2);
		}

		fileStream.Write(bytesData, 0, bytesData.Length);
	}

	static void WriteHeader(FileStream fileStream, AudioClip clip) {

		var hz = clip.frequency;
		var channels = clip.channels;
		var samples = clip.samples;

		fileStream.Seek(0, SeekOrigin.Begin);

		Byte[] riff = System.Text.Encoding.UTF8.GetBytes("RIFF");
		fileStream.Write(riff, 0, 4);

		Byte[] chunkSize = BitConverter.GetBytes(fileStream.Length - 8);
		fileStream.Write(chunkSize, 0, 4);

		Byte[] wave = System.Text.Encoding.UTF8.GetBytes("WAVE");
		fileStream.Write(wave, 0, 4);

		Byte[] fmt = System.Text.Encoding.UTF8.GetBytes("fmt ");
		fileStream.Write(fmt, 0, 4);

		Byte[] subChunk1 = BitConverter.GetBytes(16);
		fileStream.Write(subChunk1, 0, 4);

		UInt16 two = 2;
		UInt16 one = 1;

		Byte[] audioFormat = BitConverter.GetBytes(one);
		fileStream.Write(audioFormat, 0, 2);

		Byte[] numChannels = BitConverter.GetBytes(channels);
		fileStream.Write(numChannels, 0, 2);

		Byte[] sampleRate = BitConverter.GetBytes(hz);
		fileStream.Write(sampleRate, 0, 4);

		Byte[] byteRate = BitConverter.GetBytes(hz * channels * 2); // sampleRate * bytesPerSample*number of channels, here 44100*2*2
		fileStream.Write(byteRate, 0, 4);

		UInt16 blockAlign = (ushort) (channels * 2);
		fileStream.Write(BitConverter.GetBytes(blockAlign), 0, 2);

		UInt16 bps = 16;
		Byte[] bitsPerSample = BitConverter.GetBytes(bps);
		fileStream.Write(bitsPerSample, 0, 2);

		Byte[] datastring = System.Text.Encoding.UTF8.GetBytes("data");
		fileStream.Write(datastring, 0, 4);

		Byte[] subChunk2 = BitConverter.GetBytes(samples * channels * 2);
		fileStream.Write(subChunk2, 0, 4);

//		fileStream.Close();
	}
}

ConvertAndWrite has a bug, please refer to https://docs.unity3d.com/ScriptReference/AudioClip.GetData.html
var samples = new float[clip.samples];
should be fixed as
var samples = new float[clip.samples * clip.channels];

This bug results to stereo files are saved with half duration.

GetData returns data, not 'samples'. In case of mono they are equal, but in case of stereo each sample is 2 bytes of data.
To be correct, you should also rename 'samples' variable to 'data'.

ConvertAndWrite has a bug, please refer to https://docs.unity3d.com/ScriptReference/AudioClip.GetData.html var samples = new float[clip.samples]; should be fixed as var samples = new float[clip.samples * clip.channels];

This bug results to stereo files are saved with half duration.

GetData returns data, not 'samples'. In case of mono they are equal, but in case of stereo each sample is 2 bytes of data. To be correct, you should also rename 'samples' variable to 'data'.

Thanks you 👍. Helped me a lot.

Great work!

This code is just what I needed for our current project. Thank you very much!