Silverlight Speex playing at fast rate

Question

I'm using Speex to encode the raw data but after I decode the data the audio plays at a faster rate because it makes you sound like a chipmunk. I'm using NSpeex and Silverlight 4.

8kHz Sampling

Encoding Function:

    JSpeexEnc encoder = new JSpeexEnc();
    int rawDataSize = 0;
    public byte[] EncodeAudio(byte[] rawData)
    {
        var encoder = new SpeexEncoder(BandMode.Narrow);
        var inDataSize = rawData.Length / 2;
        var inData = new short[inDataSize];

        for (var index = 0; index < rawData.Length; index += 2)
        {
            inData[index / 2] = BitConverter.ToInt16(rawData, index);
        }
        inDataSize = inDataSize - inDataSize % encoder.FrameSize;

        var encodedData = new byte[rawData.Length];
        var encodedBytes = encoder.Encode(inData, 0, inDataSize, encodedData, 0, encodedData.Length);

        byte[] encodedAudioData = null;
        if (encodedBytes != 0)
        {
            encodedAudioData = new byte[encodedBytes];
            Array.Copy(encodedData, 0, encodedAudioData, 0, encodedBytes);
        }
        rawDataSize = inDataSize; // Count of encoded shorts, for debugging
        return encodedAudioData;
    }

Decoding Function:

    SpeexDecoder decoder = new SpeexDecoder(BandMode.Narrow);
    public byte[] Decode(byte[] encodedData)
    {
        try
        {
            short[] decodedFrame = new short[8000]; // should be the same number of samples as on the capturing side
            int decoderBytes = decoder.Decode(encodedData, 0, encodedData.Length, decodedFrame, 0, false);

            byte[] decodedData = new byte[encodedData.Length];
            byte[] decodedAudioData = null;

            decodedAudioData = new byte[decoderBytes * 2];
            for (int shortIndex = 0, byteIndex = 0; byteIndex < decoderBytes; shortIndex++)
            {
                BitConverter.GetBytes(decodedFrame[shortIndex + byteIndex]).CopyTo(decodedAudioData, byteIndex * 2);
                byteIndex++;
            }

            // todo: do something with the decoded data
            return decodedAudioData;
        }
        catch (Exception ex)
        {
            ShowMessageBox(ex.Message.ToString());
            return null;
        }

    }

Playing the audio:

    void PlayWave(byte[] PCMBytes)
    {
        byte[] decodedBuffer = Decode(PCMBytes);
        MemoryStream ms_PCM = new MemoryStream(decodedBuffer);
        MemoryStream ms_Wave = new MemoryStream();

        _pcm.SavePcmToWav(ms_PCM, ms_Wave, 16, 8000, 1);

        WaveMediaStreamSource WaveStream = new WaveMediaStreamSource(ms_Wave);
        mediaElement1.SetSource(WaveStream);
        mediaElement1.Play();
    }

Answer 1

Sorry guys for the late response but I figured out what the problem was.

Inside my decode function I loop through the decoded short array but I'm only copying half of the bytes into my new byte array.

It needs to look something like this:

decodedAudioData = new byte[decoderBytes * 2];
for (int shortIndex = 0, byteIndex = 0; shortIndex < decodedFrame.Length; shortIndex++, byteIndex += 2)
{
    byte[] temp = BitConverter.GetBytes(decodedFrame[shortIndex]);
    decodedAudioData[byteIndex] = temp[0];
    decodedAudioData[byteIndex + 1] = temp[1];
}