DirectSound时序和采样计数

Question

我正在使用DirectSound向音频卡写入一个正弦波。采样大小为16位，单通道。我的问题是，需要多少样本才能发出5秒的声音？采样率为每秒44100个样本。数学很简单: 220500是答案。然而，这让我抓狂，因为我的代码只运行了大约一半的时间！下面是我的代码：

using Microsoft.DirectX.DirectSound; 
using System;
namespace Audio
{
    // The class 
    public class Oscillator
    {
        static void Main(string[] args)
        {

            // Set up wave format 
            WaveFormat waveFormat = new WaveFormat();
            waveFormat.FormatTag = WaveFormatTag.Pcm;
            waveFormat.Channels = 1;
            waveFormat.BitsPerSample = 16;
            waveFormat.SamplesPerSecond = 44100;
            waveFormat.BlockAlign = (short)(waveFormat.Channels * waveFormat.BitsPerSample / 8);
            waveFormat.AverageBytesPerSecond = waveFormat.BlockAlign * waveFormat.SamplesPerSecond;

            // Set up buffer description 
            BufferDescription bufferDesc = new BufferDescription(waveFormat);
            bufferDesc.Control3D = false;
            bufferDesc.ControlEffects = false;
            bufferDesc.ControlFrequency = true;
            bufferDesc.ControlPan = true;
            bufferDesc.ControlVolume = true;
            bufferDesc.DeferLocation = true;
            bufferDesc.GlobalFocus = true;

            Device d = new Device();
            d.SetCooperativeLevel(new System.Windows.Forms.Control(), CooperativeLevel.Priority);


            int samples = 5 * waveFormat.SamplesPerSecond * waveFormat.Channels;
            char[] buffer = new char[samples];

            // Set buffer length 
            bufferDesc.BufferBytes = buffer.Length * waveFormat.BlockAlign;

            // Set initial amplitude and frequency 
            double frequency = 500;
            double amplitude = short.MaxValue / 3;
            double two_pi = 2 * Math.PI;
            // Iterate through time 
            for (int i = 0; i < buffer.Length; i++)
            {
                // Add to sine 
                buffer[i] = (char)(amplitude *
                    Math.Sin(i * two_pi * frequency / waveFormat.SamplesPerSecond));
            }

            SecondaryBuffer bufferSound = new SecondaryBuffer(bufferDesc, d);
            bufferSound.Volume = (int)Volume.Max;
            bufferSound.Write(0, buffer, LockFlag.None);
            bufferSound.Play(0, BufferPlayFlags.Default);
            System.Threading.Thread.Sleep(10000);
        }
    }
}

根据我的计算，这应该会播放5秒。它在中场休息时播放。如果我改变了

 int samples = 5 * waveFormat.SamplesPerSecond * waveFormat.Channels;

至

  int samples = 5 * waveFormat.SamplesPerSecond * waveFormat.Channels
      * waveFormat.BlockAlign;

然后声音工作正常，但这是一个黑客，不是吗？我肯定做错了什么，但我不知道是什么。

耽误您时间，实在对不起。

Answer 1

如果我没记错的话，对于16位的每个样本，你将有2个字节，因此你的缓冲区字节计数将是样本计数的两倍。