Question

Is there a way in C# to play audio (for example, MP3) direcly from a System.IO.Stream that for instance was returend from a WebRequest without saving the data temporarily to the disk?

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Solution with NAudio

With the help of NAudio 1.3 it is possible to:

1. Load an MP3 file from a URL into a MemoryStream
2. Convert MP3 data into wave data after it was completely loaded
3. Playback the wave data using NAudio‘s WaveOut class

It would have been nice to be able to even play a half loaded MP3 file, but this seems to be impossible due to the NAudio library design.

And this is the function that will do the work:

    public static void PlayMp3FromUrl(string url)     {         using (Stream ms = new MemoryStream())         {             using (Stream stream = WebRequest.Create(url)                 .GetResponse().GetResponseStream())             {                 byte[] buffer = new byte[32768];                 int read;                 while ((read = stream.Read(buffer, 0, buffer.Length)) > 0)                 {                     ms.Write(buffer, 0, read);                 }             }              ms.Position = 0;             using (WaveStream blockAlignedStream =                 new BlockAlignReductionStream(                     WaveFormatConversionStream.CreatePcmStream(                         new Mp3FileReader(ms))))             {                 using (WaveOut waveOut = new WaveOut(WaveCallbackInfo.FunctionCallback()))                 {                     waveOut.Init(blockAlignedStream);                     waveOut.Play();                                             while (waveOut.PlaybackState == PlaybackState.Playing )                                             {                         System.Threading.Thread.Sleep(100);                     }                 }             }         }     } 

Answer 1

Edit: Answer updated to reflect changes in recent versions of NAudio

It’s possible using the NAudio open source .NET audio library I have written. It looks for an ACM codec on your PC to do the conversion. The Mp3FileReader supplied with NAudio currently expects to be able to reposition within the source stream (it builds an index of MP3 frames up front), so it is not appropriate for streaming over the network. However, you can still use the MP3Frame and AcmMp3FrameDecompressor classes in NAudio to decompress streamed MP3 on the fly.

I have posted an article on my blog explaining how to play back an MP3 stream using NAudio. Essentially you have one thread downloading MP3 frames, decompressing them and storing them in a BufferedWaveProvider. Another thread then plays back using the BufferedWaveProvider as an input.