我正在使用 DynamicSoundEffectInstance 类的 MonoGame（基本上是 Xna）中制作这个游戏。MonoGame 还没有 DynamicSoundEffectInstance 的实现，所以我自己做了：
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
#if MONOMAC
using MonoMac.OpenAL;
#else
using OpenTK.Audio.OpenAL;
#endif
using System.Threading;
namespace Microsoft.Xna.Framework.Audio
{
public sealed class DynamicSoundEffectInstance : IDisposable
{
private const int BUFFERCOUNT = 2;
private SoundState soundState = SoundState.Stopped;
private AudioChannels channels;
private int sampleRate;
private ALFormat format;
private bool looped = false;
private float volume = 1.0f;
private float pan = 0;
private float pitch = 0f;
private int sourceId;
private int[] bufferIds;
private int[] bufferIdsToFill;
private int currentBufferToFill;
private bool isDisposed = false;
private bool hasSourceId = false;
private Thread bufferFillerThread = null;
// Events
public event EventHandler<EventArgs> BufferNeeded;
internal void OnBufferNeeded(EventArgs args)
{
if (BufferNeeded != null)
{
BufferNeeded(this, args);
}
}
public DynamicSoundEffectInstance(int sampleRate, AudioChannels channels)
{
this.sampleRate = sampleRate;
this.channels = channels;
switch (channels)
{
case AudioChannels.Mono:
this.format = ALFormat.Mono16;
break;
case AudioChannels.Stereo:
this.format = ALFormat.Stereo16;
break;
default:
break;
}
}
public bool IsDisposed
{
get
{
return isDisposed;
}
}
public float Pan
{
get
{
return pan;
}
set
{
pan = value;
if (hasSourceId)
{
// Listener
// Pan
AL.Source(sourceId, ALSource3f.Position, pan, 0.0f, 0.1f);
}
}
}
public float Pitch
{
get
{
return pitch;
}
set
{
pitch = value;
if (hasSourceId)
{
// Pitch
AL.Source(sourceId, ALSourcef.Pitch, XnaPitchToAlPitch(pitch));
}
}
}
public float Volume
{
get
{
return volume;
}
set
{
volume = value;
if (hasSourceId)
{
// Volume
AL.Source(sourceId, ALSourcef.Gain, volume * SoundEffect.MasterVolume);
}
}
}
public SoundState State
{
get
{
return soundState;
}
}
private float XnaPitchToAlPitch(float pitch)
{
// pitch is different in XNA and OpenAL. XNA has a pitch between -1 and 1 for one octave down/up.
// openAL uses 0.5 to 2 for one octave down/up, while 1 is the default. The default value of 0 would make it completely silent.
return (float)Math.Exp(0.69314718 * pitch);
}
public void Play()
{
if (!hasSourceId)
{
bufferIds = AL.GenBuffers(BUFFERCOUNT);
sourceId = AL.GenSource();
hasSourceId = true;
}
soundState = SoundState.Playing;
if (bufferFillerThread == null)
{
bufferIdsToFill = bufferIds;
currentBufferToFill = 0;
OnBufferNeeded(EventArgs.Empty);
bufferFillerThread = new Thread(new ThreadStart(BufferFiller));
bufferFillerThread.Start();
}
AL.SourcePlay(sourceId);
}
public void Apply3D(AudioListener listener, AudioEmitter emitter)
{
Apply3D(new AudioListener[] { listener }, emitter);
}
public void Pause()
{
if (hasSourceId)
{
AL.SourcePause(sourceId);
soundState = SoundState.Paused;
}
}
public void Apply3D(AudioListener[] listeners, AudioEmitter emitter)
{
// get AL's listener position
float x, y, z;
AL.GetListener(ALListener3f.Position, out x, out y, out z);
for (int i = 0; i < listeners.Length; i++)
{
AudioListener listener = listeners[i];
// get the emitter offset from origin
Vector3 posOffset = emitter.Position - listener.Position;
// set up orientation matrix
Matrix orientation = Matrix.CreateWorld(Vector3.Zero, listener.Forward, listener.Up);
// set up our final position and velocity according to orientation of listener
Vector3 finalPos = new Vector3(x + posOffset.X, y + posOffset.Y, z + posOffset.Z);
finalPos = Vector3.Transform(finalPos, orientation);
Vector3 finalVel = emitter.Velocity;
finalVel = Vector3.Transform(finalVel, orientation);
// set the position based on relative positon
AL.Source(sourceId, ALSource3f.Position, finalPos.X, finalPos.Y, finalPos.Z);
AL.Source(sourceId, ALSource3f.Velocity, finalVel.X, finalVel.Y, finalVel.Z);
}
}
public void Dispose()
{
if (!isDisposed)
{
Stop(true);
AL.DeleteBuffers(bufferIds);
AL.DeleteSource(sourceId);
bufferIdsToFill = null;
hasSourceId = false;
isDisposed = true;
}
}
public void Stop()
{
if (hasSourceId)
{
AL.SourceStop(sourceId);
int pendingBuffers = PendingBufferCount;
if(pendingBuffers > 0)
AL.SourceUnqueueBuffers(sourceId, PendingBufferCount);
if (bufferFillerThread != null)
bufferFillerThread.Abort();
bufferFillerThread = null;
}
soundState = SoundState.Stopped;
}
public void Stop(bool immediate)
{
Stop();
}
public TimeSpan GetSampleDuration(int sizeInBytes)
{
throw new NotImplementedException();
}
public int GetSampleSizeInBytes(TimeSpan duration)
{
int size = (int)(duration.TotalMilliseconds * ((float)sampleRate / 1000.0f));
return (size + (size & 1)) * 16;
}
public void SubmitBuffer(byte[] buffer)
{
this.SubmitBuffer(buffer, 0, buffer.Length);
}
public void SubmitBuffer(byte[] buffer, int offset, int count)
{
if (bufferIdsToFill != null) {
AL.BufferData (bufferIdsToFill [currentBufferToFill], format, buffer, count, sampleRate);
AL.SourceQueueBuffer (sourceId, bufferIdsToFill [currentBufferToFill]);
currentBufferToFill++;
if (currentBufferToFill >= bufferIdsToFill.Length)
bufferIdsToFill = null;
else
OnBufferNeeded (EventArgs.Empty);
} else {
throw new Exception ("Buffer already full.");
}
}
private void BufferFiller()
{
bool done = false;
while (!done)
{
var state = AL.GetSourceState(sourceId);
if (state == ALSourceState.Stopped || state == ALSourceState.Initial)
AL.SourcePlay(sourceId);
if (bufferIdsToFill != null)
continue;
int buffersProcessed;
AL.GetSource(sourceId, ALGetSourcei.BuffersProcessed, out buffersProcessed);
if (buffersProcessed == 0)
continue;
bufferIdsToFill = AL.SourceUnqueueBuffers(sourceId, buffersProcessed);
currentBufferToFill = 0;
OnBufferNeeded(EventArgs.Empty);
}
}
public bool IsLooped
{
get
{
return looped;
}
set
{
looped = value;
}
}
public int PendingBufferCount
{
get
{
if (hasSourceId)
{
int buffersQueued;
AL.GetSource(sourceId, ALGetSourcei.BuffersQueued, out buffersQueued);
return buffersQueued;
}
return 0;
}
}
}
}
现在，我按照本教程在 Xna 中制作动态声音，该教程与我的自定义 MonoGame 类一起使用。但是，当我运行项目（Xamarin Studio 4、Mac OS X 10.8、MonoGame 3.0.1）时，它会抛出这个异常：
Buffer already full
指向我的自定义类中的代码：
public void SubmitBuffer(byte[] buffer, int offset, int count)
{
if (bufferIdsToFill != null) {
AL.BufferData (bufferIdsToFill [currentBufferToFill], format, buffer, count, sampleRate);
AL.SourceQueueBuffer (sourceId, bufferIdsToFill [currentBufferToFill]);
currentBufferToFill++;
if (currentBufferToFill >= bufferIdsToFill.Length)
bufferIdsToFill = null;
else
OnBufferNeeded (EventArgs.Empty);
} else {
throw new Exception ("Buffer already full."); //RIGHT HERE IS THE EXCEPTION
}
}
我注释掉了异常，然后再次运行它。它播放了声音，里面有爆裂声，但它仍然在播放。如何清除缓冲区，使其未满？我完全按照本教程进行操作，所以我添加到项目中的所有代码都在其中。