Need for speed GIN to WAV converter

Program.cs

using System.IO;

internal class Program
{
    private static void Main(string[] args)
    {
        var buffer = new byte[0x4C];

        int[] samples = new int[0x20],
              coeffs1 = new int[] { 0, 0xF0, 0x1CC, 0x188 },
              coeffs2 = new int[] { 0, 0, -0xD0, -0xDC };

        using (var inFile = File.OpenRead(args[0]))
        using (var br = new BinaryReader(inFile))
        using (var outFile = File.OpenWrite($"{Path.GetFileNameWithoutExtension(args[0])}.wav"))
        using (var bw = new BinaryWriter(outFile))
        {
            inFile.Position += 0x10;

            int offset1 = br.ReadInt32(),
                offset2 = br.ReadInt32();

            inFile.Position += sizeof(int);

            int sampleRate = br.ReadInt32();

            inFile.Position += (offset1 + offset2 + 2) * 4;

            int sampleCount = (int)(inFile.Length - inFile.Position) / 0x13 * 0x20,
                samplesRead = 0;

            bw.Write(0x46464952);
            bw.Write(sampleCount * 2 + 0x24);
            bw.Write(0x20746D6645564157);
            bw.Write(0x10);
            bw.Write((short)1);
            bw.Write((short)1);
            bw.Write(sampleRate);
            bw.Write(sampleRate * 2);
            bw.Write((short)(2));
            bw.Write((short)0x10);
            bw.Write(0x61746164);
            bw.Write(sampleCount * 2);

            while (inFile.Position < inFile.Length)
            {
                int pos = (int)(inFile.Length - inFile.Position) / 0x13;

                for (int i = 0; i < pos; i++, samplesRead += 0x20)
                {
                    inFile.Read(buffer, 0, 0x13);

                    samples[0] = (short)(buffer[0] & 0xF0 | buffer[1] << 8);
                    samples[1] = (short)(buffer[2] & 0xF0 | buffer[3] << 8);

                    int coeffsOffset = buffer[0] & 0xF,
                        subFactor    = buffer[2] & 0xF;

                    for (int sampleIndex = 2; sampleIndex < 0x20; sampleIndex += 2)
                    {
                        int samp1 = (buffer[3 + sampleIndex / 2] & 0xF0) >> 4;

                        if (samp1 > 7) samp1 -= 0x10;

                        int samp2 = samples[sampleIndex - 1] * coeffs1[coeffsOffset] + 
                                    samples[sampleIndex - 2] * coeffs2[coeffsOffset];

                        samples[sampleIndex] = samp2 + (samp1 << 0x14 - subFactor) + 0x80 >> 8;

                        if (samples[sampleIndex] >  0x7FFF) samples[sampleIndex] =  0x7FFF;
                        if (samples[sampleIndex] < -0x8000) samples[sampleIndex] = -0x8000;

                        int samp3 = buffer[3 + sampleIndex / 2] & 0xF;

                        if (samp3 > 7) samp3 -= 0x10;

                        int samp4 = samples[sampleIndex]     * coeffs1[coeffsOffset] + 
                                    samples[sampleIndex - 1] * coeffs2[coeffsOffset];

                        samples[sampleIndex + 1] = samp4 + (samp3 << 0x14 - subFactor) + 0x80 >> 8;

                        if (samples[sampleIndex + 1] >  0x7FFF) samples[sampleIndex + 1] =  0x7FFF;
                        if (samples[sampleIndex + 1] < -0x8000) samples[sampleIndex + 1] = -0x8000;
                    }

                    for (int j = 0; j < 0x20; j++)
                        bw.Write((short)samples[j]);
                }
            }
        }
    }
}