我想使用NET提供的播放从网上下载的MP3文件系统.媒体.SoundPlayer机制。由于它适用于 WAV 格式,因此需要以下支持:NAudio库 - 我需要将 MP3 转换为 WAV。
我想在内存中执行所有操作,因为我需要它快速,但我有问题。下面我展示了按预期工作的代码,但它与文件配合。相反,我需要使其仅使用内存操作来工作。
(1) 有效,但涉及磁盘操作:
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) 不起作用 - 没有抛出异常,但没有播放任何内容:
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 ? */
}
}
}
}
}
}
}
如何做到这一点以及第二个代码示例有什么问题?
根据 Lee Harrison 的回答,我创建了更好的替代代码。
(3)直接播放WEB上的MP3文件,无需转换为WAV,也无需使用磁盘操作:
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) */
}
}
}
}
}
}
}
}
尽管如此(尽管这对我来说非常好),我仍然不知道示例(2)有什么问题。
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