我正在使用 Naudios Demo 应用程序来演示一下。我发现当我播放一些 mp3 文件时，最后 om 声音/mp3 我得到了一个
错误 nullreferenceexception 未处理 nullreferenceexception 对象引用未设置为对象的实例
在文件 Mp3FrameDecompressor.cs
using System;
using System.Collections.Generic;
using System.Text;
using NAudio.Wave;
using NAudio.Wave.Compression;
using System.Diagnostics;
namespace NAudio.Wave
{
/// <summary>
/// MP3 Frame Decompressor using ACM
/// </summary>
public class AcmMp3FrameDecompressor : IDisposable, IMp3FrameDecompressor
{
private AcmStream conversionStream;
private WaveFormat pcmFormat;
/// <summary>
/// Creates a new ACM frame decompressor
/// </summary>
/// <param name="sourceFormat">The MP3 source format</param>
public AcmMp3FrameDecompressor(WaveFormat sourceFormat)
{
this.pcmFormat = AcmStream.SuggestPcmFormat(sourceFormat);
conversionStream = new AcmStream(sourceFormat, pcmFormat);
}
/// <summary>
/// Output format (PCM)
/// </summary>
public WaveFormat OutputFormat { get { return pcmFormat; } }
/// <summary>
/// Decompresses a frame
/// </summary>
/// <param name="frame">The MP3 frame</param>
/// <param name="dest">destination buffer</param>
/// <param name="destOffset">Offset within destination buffer</param>
/// <returns>Bytes written into destination buffer</returns>
public int DecompressFrame(Mp3Frame frame, byte[] dest, int destOffset)
{
Array.Copy(frame.RawData, conversionStream.SourceBuffer, frame.FrameLength);
int sourceBytesConverted = 0;
int converted = conversionStream.Convert(frame.FrameLength, out sourceBytesConverted);
if (sourceBytesConverted != frame.FrameLength)
{
throw new InvalidOperationException(String.Format("Couldn't convert the whole MP3 frame (converted {0}/{1})",
sourceBytesConverted, frame.FrameLength));
}
Array.Copy(conversionStream.DestBuffer, 0, dest, destOffset, converted);
return converted;
}
/// <summary>
/// Disposes of this MP3 frame decompressor
/// </summary>
public void Dispose()
{
if (this.conversionStream != null)
{
this.conversionStream.Dispose();
this.conversionStream = null;
}
}
}
}
这是我使用的表格
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using NAudio.Wave;
using System.Net;
using System.Threading;
using System.Net.Sockets;
using System.IO;
using System.Diagnostics;
using System.ComponentModel.Composition;
namespace NAudioDemo
{
public partial class MP3StreamingPanel : Form
{
public MP3StreamingPanel()
{
InitializeComponent();
this.volumeSlider1.VolumeChanged += new EventHandler(volumeSlider1_VolumeChanged);
this.Disposed += this.MP3StreamingPanel_Disposing;
}
enum StreamingPlaybackState
{
Stopped,
Playing,
Buffering,
Paused
}
void volumeSlider1_VolumeChanged(object sender, EventArgs e)
{
if (this.volumeProvider != null)
{
this.volumeProvider.Volume = this.volumeSlider1.Volume;
}
}
private BufferedWaveProvider bufferedWaveProvider;
private IWavePlayer waveOut;
private volatile StreamingPlaybackState playbackState;
private volatile bool fullyDownloaded;
private HttpWebRequest webRequest;
private VolumeWaveProvider16 volumeProvider;
delegate void ShowErrorDelegate(string message);
private void ShowError(string message)
{
if (this.InvokeRequired)
{
this.BeginInvoke(new ShowErrorDelegate(ShowError), message);
}
else
{
MessageBox.Show(message);
}
}
private void StreamMP3(object state)
{
this.fullyDownloaded = false;
string url = (string)state;
webRequest = (HttpWebRequest)WebRequest.Create(url);
HttpWebResponse resp = null;
try
{
resp = (HttpWebResponse)webRequest.GetResponse();
}
catch(WebException e)
{
if (e.Status != WebExceptionStatus.RequestCanceled)
{
ShowError(e.Message);
}
return;
}
byte[] buffer = new byte[16384 * 4]; // needs to be big enough to hold a decompressed frame
IMp3FrameDecompressor decompressor = null;
try
{
using (var responseStream = resp.GetResponseStream())
{
var readFullyStream = new ReadFullyStream(responseStream);
do
{
if (bufferedWaveProvider != null && bufferedWaveProvider.BufferLength - bufferedWaveProvider.BufferedBytes < bufferedWaveProvider.WaveFormat.AverageBytesPerSecond / 4)
{
Debug.WriteLine("Buffer getting full, taking a break");
Thread.Sleep(500);
}
else
{
Mp3Frame frame = null;
try
{
frame = Mp3Frame.LoadFromStream(readFullyStream);
}
catch (EndOfStreamException)
{
this.fullyDownloaded = true;
// reached the end of the MP3 file / stream
break;
}
catch (WebException)
{
// probably we have aborted download from the GUI thread
break;
}
if (decompressor == null)
{
// don't think these details matter too much - just help ACM select the right codec
// however, the buffered provider doesn't know what sample rate it is working at
// until we have a frame
WaveFormat waveFormat = new Mp3WaveFormat(frame.SampleRate, frame.ChannelMode == ChannelMode.Mono ? 1 : 2, frame.FrameLength, frame.BitRate);
decompressor = new AcmMp3FrameDecompressor(waveFormat);
this.bufferedWaveProvider = new BufferedWaveProvider(decompressor.OutputFormat);
this.bufferedWaveProvider.BufferDuration = TimeSpan.FromSeconds(20); // allow us to get well ahead of ourselves
//this.bufferedWaveProvider.BufferedDuration = 250;
}
int decompressed = decompressor.DecompressFrame(frame, buffer, 0);
//Debug.WriteLine(String.Format("Decompressed a frame {0}", decompressed));
bufferedWaveProvider.AddSamples(buffer, 0, decompressed);
}
} while (playbackState != StreamingPlaybackState.Stopped);
Debug.WriteLine("Exiting");
// was doing this in a finally block, but for some reason
// we are hanging on response stream .Dispose so never get there
decompressor.Dispose();
}
}
finally
{
if (decompressor != null)
{
decompressor.Dispose();
}
}
}
private void buttonPlay_Click(object sender, EventArgs e)
{
if (playbackState == StreamingPlaybackState.Stopped)
{
playbackState = StreamingPlaybackState.Buffering;
this.bufferedWaveProvider = null;
ThreadPool.QueueUserWorkItem(new WaitCallback(StreamMP3), textBoxStreamingUrl.Text);
timer1.Enabled = true;
}
else if (playbackState == StreamingPlaybackState.Paused)
{
playbackState = StreamingPlaybackState.Buffering;
}
}
private void StopPlayback()
{
if (playbackState != StreamingPlaybackState.Stopped)
{
if (!fullyDownloaded)
{
webRequest.Abort();
}
this.playbackState = StreamingPlaybackState.Stopped;
if (waveOut != null)
{
waveOut.Stop();
waveOut.Dispose();
waveOut = null;
}
timer1.Enabled = false;
// n.b. streaming thread may not yet have exited
Thread.Sleep(500);
ShowBufferState(0);
}
}
private void ShowBufferState(double totalSeconds)
{
}
private void timer1_Tick(object sender, EventArgs e)
{
if (playbackState != StreamingPlaybackState.Stopped)
{
if (this.waveOut == null && this.bufferedWaveProvider != null)
{
Debug.WriteLine("Creating WaveOut Device");
this.waveOut = CreateWaveOut();
waveOut.PlaybackStopped += waveOut_PlaybackStopped;
this.volumeProvider = new VolumeWaveProvider16(bufferedWaveProvider);
this.volumeProvider.Volume = this.volumeSlider1.Volume;
waveOut.Init(volumeProvider);
progressBarBuffer.Maximum = (int)bufferedWaveProvider.BufferDuration.TotalMilliseconds;
}
else if (bufferedWaveProvider != null)
{
var bufferedSeconds = bufferedWaveProvider.BufferedDuration.TotalSeconds;
ShowBufferState(bufferedSeconds);
// make it stutter less if we buffer up a decent amount before playing
if (bufferedSeconds < 0.5 && this.playbackState == StreamingPlaybackState.Playing && !this.fullyDownloaded)
{
this.playbackState = StreamingPlaybackState.Buffering;
waveOut.Pause();
Debug.WriteLine(String.Format("Paused to buffer, waveOut.PlaybackState={0}", waveOut.PlaybackState));
}
else if (bufferedSeconds > 1 && this.playbackState == StreamingPlaybackState.Buffering)
{
waveOut.Play();
Debug.WriteLine(String.Format("Started playing, waveOut.PlaybackState={0}", waveOut.PlaybackState));
this.playbackState = StreamingPlaybackState.Playing;
}
else if (this.fullyDownloaded && bufferedSeconds == 0)
{
Debug.WriteLine("Reached end of stream");
StopPlayback();
}
}
}
}
private IWavePlayer CreateWaveOut()
{
return new WaveOut();
//return new DirectSoundOut();
}
private void MP3StreamingPanel_Disposing(object sender, EventArgs e)
{
StopPlayback();
}
private void buttonPause_Click(object sender, EventArgs e)
{
if (playbackState == StreamingPlaybackState.Playing || playbackState == StreamingPlaybackState.Buffering)
{
waveOut.Pause();
Debug.WriteLine(String.Format("User requested Pause, waveOut.PlaybackState={0}", waveOut.PlaybackState));
playbackState = StreamingPlaybackState.Paused;
}
}
private void buttonStop_Click(object sender, EventArgs e)
{
StopPlayback();
}
private void waveOut_PlaybackStopped(object sender, StoppedEventArgs e)
{
Debug.WriteLine("Playback Stopped");
if (e.Exception != null)
{
MessageBox.Show(String.Format("Playback Error {0}", e.Exception.Message));
}
}
}
[Export(typeof(INAudioDemoPlugin))]
public class MP3StreamingPanelPlugin : INAudioDemoPlugin
{
public string Name
{
get { return "MP3 Streaming"; }
}
public Control CreatePanel()
{
return new MP3StreamingPanel();
}
}
}
我在这条线上得到了错误
Array.Copy(frame.RawData, conversionStream.SourceBuffer, frame.FrameLength);