How to decode RTP packets and save it has .wav file

问题

I am trying to develop an application in which a sip call is established and then i am capturing rtp audio packets. As they are encoded so i need to decode them and save it has .wav file. Tried using NAudio but didnt worked. Is there any solution using NAudio or any other source to solve this problem...

the code i used is as follow. data is the byte array in which rtp packet data is.

System.IO.MemoryStream stream = new System.IO.MemoryStream(data);

RawSourceWaveStream rsws = new RawSourceWaveStream(stream, WaveFormat.CreateMuLawFormat(8000,1));

WaveStream conversionStream = WaveFormatConversionStream.CreatePcmStream(rsws);

WaveStream blockAlignedStream = new BlockAlignReductionStream(conversionStream);

byte[] buffer = new byte[udpHeader.Data.Length];
blockAlignedStream.Read(buffer, 0, udpHeader.Data.Length);
writer.WriteData(buffer, 0, buffer.Length);

Thanks in Advance.

回答1:

Better late than never!

Use the following helper classs by Mark Heath from Using NAudio to decode mu-law audio

    public class RawSourceWaveStream : WaveStream
    {
        private Stream sourceStream;
        private WaveFormat waveFormat;

        public RawSourceWaveStream(Stream sourceStream, WaveFormat waveFormat)
        {
            this.sourceStream = sourceStream;
            this.waveFormat = waveFormat;
        }

        public override WaveFormat WaveFormat
        {
            get { return this.waveFormat; }
        }

        public override long Length
        {
            get { return this.sourceStream.Length; }
        }

        public override long Position
        {
            get
            {
                return this.sourceStream.Position;
            }
            set
            {
                this.sourceStream.Position = value;
            }
        }

        public override int Read(byte[] buffer, int offset, int count)
        {
            return sourceStream.Read(buffer, offset, count);
        }
    }

Get the latest NAudio.dll and NAudio.WindowsMediaFormat.dll

from

http://naudio.codeplex.com/

Then do the following to convert from U-Law or Mu-Law to Wav:

Stream tmpMemStream = new FileStream(Server.MapPath("/input/") + "input.voc", FileMode.Open, FileAccess.Read);
var waveFormat = WaveFormat.CreateMuLawFormat(8000, 1);  // Feel free to tweak this number
var reader = new RawSourceWaveStream(tmpMemStream, waveFormat);
using (WaveStream convertedStream = WaveFormatConversionStream.CreatePcmStream(reader))
{
    WaveFileWriter.CreateWaveFile(Server.MapPath("/output/") + "output.wav", convertedStream);
}
tmpMemStream.Close();

Just remember to respect the privacy of the owners of those audio files!

来源：https://stackoverflow.com/questions/6951949/how-to-decode-rtp-packets-and-save-it-has-wav-file

标签

sip

rtp

naudio

wav