[Speex-dev] Decoding producing garbled sound

Vinod Vijayan vinod at speechdesk.com
Tue Jan 11 04:37:45 PST 2005

 I am back. Thanks everybody for their suggestions.
 Finally I could get something out of the decoder that
 makes sense. But the problem is it is highly noisy and the
 voice is not very clear. Normally without using the codec I
 get good audible sound through the Microphone.

 I'm using Speex version 1.1.6. I've also used 1.0.4 beforehand
 and experienced the same problem with it.

 1. I record my audio at mono 8000Hz, 16bits per sample.

 2. I encode frame-sized (320 bytes) fragments.

 char *encode(char *buffer, int &encodeSize)
	char    *encodedBuffer    = new char[160];
        short   speexShort;
 	float   *speexFloat       = new float[160];

     // Convert the audio to a short then to a float buffer
       for (int i = 0; i < 160; i++)
             memcpy(&speexShort, &buffer[i*2], sizeof(short));
             speexFloat[i] = speexShort;

       // Encode the sound data using the float buffer
       speex_encode(mEncode, speexFloat, &mBits);
       encodeSize = speex_bits_write(&mBits, encodedBuffer, 160);

       delete[] speexFloat;
       speexFloat = 0;

       // Return the encoded buffer
       return encodedBuffer;

 3.I immediately decode the encoded buffer. Encoded size is always 38 bytes
   for this sample set and expected decoded size is 320 bytes

 char *CRecNplayDlg::decode(char *buffer, int encodeSize)
    char *decodedBuffer = new char[320];
    void *mDecode       = speex_decoder_init(&speex_nb_mode);
    short speexShort;

    float *speexFloat = new float[160];

    // Decode the sound data into a float buffer

    speex_bits_read_from(&dBits, buffer, encodeSize);
    speex_decode(mDecode, &dBits, speexFloat);

    // Convert from float to short to char
    for (int i = 0, j=0; i < 160; i++, j++)
             speexShort = speexFloat[i];
             memcpy(&decodedBuffer[j*2], &speexShort, sizeof(short));
    delete[] speexFloat;
    // Return the buffer
    return decodedBuffer;

I have tried every way possible but it isn't helping so I had no option
but to post my problem. I tried debugging the speexenc and speexdec
projects but it was of no help. Now what happens is this :-

Encoding side
 char[320] -> float[160]  >>encoding>> char[38]

Decoding side
 char[38] >>decoding>> float[160] -> char[320]

If the above looks fine then where am i going wrong. Plz can anybody
who faced the same problem as mine help. Thanks.

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