WaveSaver.cs

namespace Audio
{
	using System;
	using System.IO;

	/// <summary>
	/// Provides methods for saving byte arrays of audio samples to a wav file in mono or stereo.
	/// </summary>
	public static class WaveSaver
	{
		/// <summary>
		/// Saves the waveform as a mono audio file in wav format.
		/// </summary>
		/// <param name="samples">The individual samples that make up the waveform.</param>
		/// <param name="filename">The filename of the output wav file.</param>
		public static void SaveToWave(short[] samples, string filename)
		{
			const short NumberOfChannels = 1; // mono audio
			const short BytesPerSample = 2;   // 16bit samples
			const int SamplingRate = 44100;   // 44.1 kHz
			int totalBytes = checked(44 + (samples.Length * BytesPerSample * NumberOfChannels)); // size of headers + data
			var output = new byte[totalBytes];
			Buffer.BlockCopy(GetLEBytes(0x46464952), 0, output, 0, 4);  // "RIFF"
			Buffer.BlockCopy(GetLEBytes(totalBytes - 8), 0, output, 4, 4);  // RIFF chunk size
			Buffer.BlockCopy(GetLEBytes(0x45564157), 0, output, 8, 4);  // "WAVE"
			Buffer.BlockCopy(GetLEBytes(0x20746D66), 0, output, 12, 4); // "fmt "
			Buffer.BlockCopy(GetLEBytes(16), 0, output, 16, 4); // fmt chunk size
			Buffer.BlockCopy(GetLEBytes((short)1), 0, output, 20, 2);   // compression code (1 - PCM/Uncompressed)
			Buffer.BlockCopy(GetLEBytes((short)NumberOfChannels), 0, output, 22, 2);   // number of channels
			Buffer.BlockCopy(GetLEBytes(SamplingRate), 0, output, 24, 4);   // sampling rate
			Buffer.BlockCopy(GetLEBytes(SamplingRate * BytesPerSample * NumberOfChannels), 0, output, 28, 4);   // bytes/second
			Buffer.BlockCopy(GetLEBytes((short)(BytesPerSample * NumberOfChannels)), 0, output, 32, 2);   // block size
			Buffer.BlockCopy(GetLEBytes((short)(BytesPerSample * 8)), 0, output, 34, 2);  // bits per sample
			Buffer.BlockCopy(GetLEBytes(0x61746164), 0, output, 36, 4); // "data"
			Buffer.BlockCopy(GetLEBytes(totalBytes - 44), 0, output, 40, 4);    // data chunk size
			for (var i = 0; i < samples.Length; i++)
			{
				Buffer.BlockCopy(GetLEBytes(samples[i]), 0, output, (BytesPerSample * i * NumberOfChannels) + 44, BytesPerSample);
			}

			File.WriteAllBytes(filename, output);
		}

		/// <summary>
		/// Saves the waveform as a stereo audio file in wav format.
		/// </summary>
		/// <param name="leftSamples">The individual samples that make up the left channel of the waveform.</param>
		/// <param name="rightSamples">The individual samples that make up the right channel of the waveform.</param>
		/// <param name="filename">The filename of the output wav file.</param>
		public static void SaveToWave(short[] leftSamples, short[] rightSamples, string filename)
		{
			const short NumberOfChannels = 2; // stereo audio
			const short BytesPerSample = 2;   // 16bit samples
			const int SamplingRate = 44100;   // 44.1 kHz
			var shortChannel = (leftSamples.Length < rightSamples.Length) ? leftSamples : rightSamples;
			int totalBytes = checked(44 + (shortChannel.Length * BytesPerSample * NumberOfChannels)); // size of headers + data
			var output = new byte[totalBytes];
			Buffer.BlockCopy(GetLEBytes(0x46464952), 0, output, 0, 4);  // "RIFF"
			Buffer.BlockCopy(GetLEBytes(totalBytes - 8), 0, output, 4, 4);  // RIFF chunk size
			Buffer.BlockCopy(GetLEBytes(0x45564157), 0, output, 8, 4);  // "WAVE"
			Buffer.BlockCopy(GetLEBytes(0x20746D66), 0, output, 12, 4); // "fmt "
			Buffer.BlockCopy(GetLEBytes(16), 0, output, 16, 4); // fmt chunk size
			Buffer.BlockCopy(GetLEBytes((short)1), 0, output, 20, 2);   // compression code (1 - PCM/Uncompressed)
			Buffer.BlockCopy(GetLEBytes((short)NumberOfChannels), 0, output, 22, 2);   // number of channels
			Buffer.BlockCopy(GetLEBytes(SamplingRate), 0, output, 24, 4);   // sampling rate
			Buffer.BlockCopy(GetLEBytes(SamplingRate * BytesPerSample * NumberOfChannels), 0, output, 28, 4);   // bytes/second
			Buffer.BlockCopy(GetLEBytes((short)(BytesPerSample * NumberOfChannels)), 0, output, 32, 2);   // block size
			Buffer.BlockCopy(GetLEBytes((short)(BytesPerSample * 8)), 0, output, 34, 2);  // bits per sample
			Buffer.BlockCopy(GetLEBytes(0x61746164), 0, output, 36, 4); // "data"
			Buffer.BlockCopy(GetLEBytes(totalBytes - 44), 0, output, 40, 4);    // data chunk size
			for (var i = 0; i < shortChannel.Length; i++)
			{
				Buffer.BlockCopy(GetLEBytes(leftSamples[i]), 0, output, (BytesPerSample * i * NumberOfChannels) + 44, BytesPerSample);
				Buffer.BlockCopy(GetLEBytes(rightSamples[i]), 0, output, (BytesPerSample * i * NumberOfChannels) + 44 + BytesPerSample, BytesPerSample);
			}

			File.WriteAllBytes(filename, output);
		}

		/// <summary>
		/// Gets a <c>byte</c> array that represents the specified <c>short</c> in little endian.
		/// </summary>
		/// <param name="value">The value to represent in the <c>byte</c> array.</param>
		/// <returns>The <c>byte</c> array.</returns>
		private static byte[] GetLEBytes(short value)
		{
			if (BitConverter.IsLittleEndian)
			{
				return BitConverter.GetBytes(value);
			}
			else
			{
				return BitConverter.GetBytes((short)((value & 0xFF) << 8 | (value & 0xFF00) >> 8));
			}
		}

		/// <summary>
		/// Gets a <c>byte</c> array that represents the specified <c>int</c> in little endian.
		/// </summary>
		/// <param name="value">The value to represent in the <c>byte</c> array.</param>
		/// <returns>The <c>byte</c> array.</returns>
		private static byte[] GetLEBytes(int value)
		{
			if (BitConverter.IsLittleEndian)
			{
				return BitConverter.GetBytes(value);
			}
			else
			{
				return BitConverter.GetBytes((int)((value & 0xFF) << 24) | (int)((value & 0xFF00) << 8)
					| (int)((value & 0xFF0000) >> 8) | (int)((value & 0xFF000000) >> 24));
			}
		}
	}
}