我要玩使用NET所提供的 System.Media.SoundPlayer 机制。由于它与WAV格式，它需要如支持 n音讯库 - 我需要MP3转换为WAV。

I want to play MP3 file downloaded from the web using NET provided System.Media.SoundPlayer mechanism. As it works with WAV formats, it requires the support of e.g. NAudio library - I need to convert MP3 to WAV.

我想要做的所有操作在内存中，因为我需要它来进行所谓的快，但我有问题。下面我已经证明code的正常工作，但它与文件配合。相反，我需要它的工作只使用内存操作。

I want to do all operations in memory, as I need it to be so called fast, but I have problems. Below I've shown code which works as expected, but it cooperates with files. Instead I need to make it working using memory operations only.

（1）工作，但涉及磁盘操作：

(1) works, but involves disk operations:

public void Speak(Uri mp3FileUri)
{
    using (var client = new WebClient())
    {
        using (var networkStream = client.OpenRead(mp3FileUri))
        {
            if (networkStream != null)
            {
                var temp = Path.GetTempPath();
                var mp3File = Path.Combine(temp, "file.mp3");
                var wavFile = Path.Combine(temp, "file.wav");
                using (var fileStream = File.Create(mp3File))
                {
                    networkStream.CopyTo(fileStream);
                }
                using (var reader = new Mp3FileReader(mp3File))
                {
                    WaveFileWriter.CreateWaveFile(wavFile, reader);
                }                        
                using(var player = new SoundPlayer(wavFile))
                {
                    player.Play();
                }
            }
        }
    }
}

（2）不工作 - 不会抛出异常，但没有播放：

(2) doesn't work - no exception is thrown, but nothing is played:

public void Speak(Uri mp3FileUri)
{
    using (var client = new WebClient())
    {
        using (var networkStream = client.OpenRead(mp3FileUri))
        {
            if (networkStream != null)
            {
                var memStream = new MemoryStream();
                networkStream.CopyTo(memStream);
                memStream.Position = 0;
                using (var reader = new Mp3FileReader(memStream))
                {
                    var outStream = new MemoryStream();
                    using (var writer = new WaveFileWriter(outStream, reader.WaveFormat))
                    {
                        var num = 0L;
                        var buffer = new byte[reader.WaveFormat.AverageBytesPerSecond * 4];
                        while (true)
                        {
                            var count = reader.Read(buffer, 0, buffer.Length);
                            if (count != 0)
                            {
                                num += count;
                                if (num <= int.MaxValue)
                                    writer.Write(buffer, 0, count);
                                else
                                    throw new InvalidOperationException("Too large file or endless stream.");
                            }
                            else
                                break;
                        }
                        writer.Flush();
                        outStream.Position = 0;
                        using(var player = new SoundPlayer(outStream))
                        {
                            player.Play(); /* why silence ? */
                        }
                    }                            
                }
            }
        }
    }
}

怎样才可以做的，什么是错的第二个code样？

How can it be done and what is wrong with the second code sample ?

推荐答案

根据李哈里森回答，我创建了替代code这是更好的。

Based on Lee Harrison answer, I've created alternative code which is better.

（3）直接播放MP3文件从WEB无需转换为WAV和无磁盘操作的用法：

(3) plays directly MP3 file from WEB without conversion to WAV and without usage of disk operations:

public void Speak(Uri mp3FileUri)
{
    using (var client = new WebClient())
    {
        using (var networkStream = client.OpenRead(mp3FileUri))
        {
            if (networkStream != null)
            {
                using (var memStream = new MemoryStream())
                {
                    networkStream.CopyTo(memStream);
                    memStream.Position = 0;                            
                    using (var waveOut = new WaveOut(WaveCallbackInfo.FunctionCallback()))
                    {
                        var waveEvent = new ManualResetEvent(false);
                        waveOut.PlaybackStopped += (sender, e) => waveEvent.Set();
                        waveEvent.Reset();
                        using (var rdr = new Mp3FileReader(memStream))
                        using (var waveStream = WaveFormatConversionStream.CreatePcmStream(rdr))
                        using (var baStream = new BlockAlignReductionStream(waveStream))
                        {
                            waveOut.Init(baStream);
                            waveOut.Play();
                            if (waveOut.PlaybackState != PlaybackState.Stopped)
                            { 
                                waveEvent.WaitOne(); /* block thread for a while because I don't want async play back                                
                                                        (to be analogical as usage of SoundPlayer Play method) */
                            }
                        }
                    }
                }
            }
        }
    }
}

不过（尽管这对我来说是相当不错的），我仍然不知道有什么用样品的问题（2）。

Nevertheless (despite this is quite good for me), I still don't know what's the problem with sample (2).