我尝试使用DirectSound和C#将声音样本从麦克风流式传输到扬声器。它应该类似于“听麦克风”，但后来我想用它来做其他事情。通过测试我的方法，我注意到背景中有无声的搔痒声和噼啪声。我猜这与写入和播放缓冲区之间的延迟有关，该延迟必须大于写入块的延迟。
如果我将录制和播放之间的延迟设置为小于 50 毫秒。大多数情况下它都有效，但有时我会听到非常响亮的开裂声。所以我决定延迟至少 50 毫秒。这对我来说没问题，但是系统“听设备”的延迟似乎要短得多。我猜它大约是 15-30 毫秒，几乎不明显。对于 50 毫秒，我至少得到一点混响效果。
在下面，我将向您展示我的麦克风代码（部分）：初始化是这样完成的：
capture = new Capture(device);
// Creating the buffer
// Determining the buffer size
bufferSize = format.AverageBytesPerSecond * bufferLength / 1000;
while (bufferSize % format.BlockAlign != 0) bufferSize += 1;
chunkSize = Math.Max(bufferSize, 256);
bufferSize = chunkSize * BUFFER_CHUNKS;
this.bufferLength = chunkSize * 1000 / format.AverageBytesPerSecond; // Redetermining the buffer Length that will be used.
captureBufferDescription = new CaptureBufferDescription();
captureBufferDescription.BufferBytes = bufferSize;
captureBufferDescription.Format = format;
captureBuffer = new CaptureBuffer(captureBufferDescription, capture);
// Creating Buffer control
bufferARE = new AutoResetEvent(false);
// Adding notifier to buffer.
bufferNotify = new Notify(captureBuffer);
BufferPositionNotify[] bpns = new BufferPositionNotify[BUFFER_CHUNKS];
for(int i = 0 ; i < BUFFER_CHUNKS ; i ++) bpns[i] = new BufferPositionNotify() { Offset = chunkSize * (i+1) - 1, EventNotifyHandle = bufferARE.SafeWaitHandle.DangerousGetHandle() };
bufferNotify.SetNotificationPositions(bpns);
捕获将在一个额外的线程中像这样运行：
// Initializing
MemoryStream tempBuffer = new MemoryStream();
// Capturing
while (isCapturing && captureBuffer.Capturing)
{
bufferARE.WaitOne();
if (isCapturing && captureBuffer.Capturing)
{
captureBuffer.Read(currentBufferPart * chunkSize, tempBuffer, chunkSize, LockFlag.None);
ReportChunk(applyVolume(tempBuffer.GetBuffer()));
currentBufferPart = (currentBufferPart + 1) % BUFFER_CHUNKS;
tempBuffer.Dispose();
tempBuffer = new MemoryStream(); // Reset Buffer;
}
}
// Finalizing
isCapturing = false;
tempBuffer.Dispose();
captureBuffer.Stop();
if (bufferARE.WaitOne(bufferLength + 1)) currentBufferPart = (currentBufferPart + 1) % BUFFER_CHUNKS; // That on next start the correct bufferpart will be read.
stateControlARE.Set();
捕获ReportChunk时将数据作为可以订阅的事件发送给扬声器。扬声器部分初始化如下：
// Creating the dxdevice.
dxdevice = new Device(device);
dxdevice.SetCooperativeLevel(hWnd, CooperativeLevel.Normal);
// Creating the buffer
bufferDescription = new BufferDescription();
bufferDescription.BufferBytes = bufferSize;
bufferDescription.Format = input.Format;
bufferDescription.ControlVolume = true;
bufferDescription.GlobalFocus = true; // That sound doesn't stop if the hWnd looses focus.
bufferDescription.StickyFocus = true; // - " -
buffer = new SecondaryBuffer(bufferDescription, dxdevice);
chunkQueue = new Queue<byte[]>();
// Creating buffer control
bufferARE = new AutoResetEvent(false);
// Register at input device
input.ChunkCaptured += new AInput.ReportBuffer(input_ChunkCaptured);
数据由事件方法放入队列中，只需：
chunkQueue.Enqueue(buffer);
bufferARE.Set();
填充播放缓冲区和启动/停止播放缓冲区由另一个线程完成：
// Initializing
int wp = 0;
bufferARE.WaitOne(); // wait for first chunk
// Playing / writing data to play buffer.
while (isPlaying)
{
Thread.Sleep(1);
bufferARE.WaitOne(BufferLength * 3); // If a chunk is played and there is no new chunk we try to continue and may stop playing, else may the buffer runs out.
// Note that this may fails if the sender was interrupted within one chunk
if (isPlaying)
{
if (chunkQueue.Count > 0)
{
while (chunkQueue.Count > 0) wp = writeToBuffer(chunkQueue.Dequeue(), wp);
if (buffer.PlayPosition > wp - chunkSize * 3 / 2) buffer.SetCurrentPosition(((wp - chunkSize * 2 + bufferSize) % bufferSize));
if (!buffer.Status.Playing)
{
buffer.SetCurrentPosition(((wp - chunkSize * 2 + bufferSize) % bufferSize)); // We have 2 chunks buffered so we step back 2 chunks and play them while getting new chunks.
buffer.Play(0, BufferPlayFlags.Looping);
}
}
else
{
buffer.Stop();
bufferARE.WaitOne(); // wait for a filling chunk
}
}
}
// Finalizing
isPlaying = false;
buffer.Stop();
stateControlARE.Set();
writeToBuffer简单地将入队的块写入缓冲区，this.buffer.Write(wp, data, LockFlag.None);并关心bufferSizeand chunkSize，wp它表示最后的写入位置。我认为这就是我的代码重要的一切。也许定义丢失了，至少还有另一种方法可以启动/停止=控制线程。
我已经发布了这段代码，以防我在填充缓冲区时出错或我的初始化错误。但我猜这个问题的发生是因为 C# 字节码的执行太慢或类似的东西。但最后我的问题仍然悬而未决：我的问题是如何减少延迟以及如何避免不应该存在的噪音？