[Speex-dev] Integrating speex with VideoNet application: Constantbackground noise

John Miles jmiles at pop.net
Thu Nov 2 08:32:43 PST 2006

Yes, it's necessary; Speex will encode signed 16-bit PCM data and decode to
the same format.  See the examples that come with it.

8-bit audio is not something you would ever want to use.

-- john
RAD Game Tools
  -----Original Message-----
  From: Carine Liang [mailto:carineliang at yahoo.com.sg]
  Sent: Thursday, November 02, 2006 12:18 AM
  To: John Miles; speex-dev at xiph.org
  Subject: Re: [Speex-dev] Integrating speex with VideoNet application:
Constantbackground noise

  Hi John,

  Thanks for your reply.

  Yes, my output device is in 8-bit mode, same as my input mode. I'm
actually working in char (8 bit) arrays. Is it necessary to work in signed
short integers only? I changed all the short arrays in the example to char.


  ----- Original Message ----
  From: John Miles <jmiles at pop.net>
  To: carineliang at yahoo.com.sg; speex-dev at xiph.org
  Sent: Thursday, 2 November 2006 2:04:39 PM
  Subject: RE: [Speex-dev] Integrating speex with VideoNet application:
Constantbackground noise

  At first glance it looks like you are opening the output device in 8-bit
mode (m_waveFormatEx.wBitsPerSample =8;).  You will need to use 16-bit mode
if you expect to write an array of signed short integers to the audio
buffer..  8-bit PCM is an unsigned mode, no longer used much these days.

  Also, a good debugging trick is to include something like this in your
output sample processing loop:

      static FILE *hack = fopen("test.raw","wb");
      fwrite(output, 2, FRAME_SIZE, hack);

  After your app is closed, there will be a file called "test.raw" in its
working directory, which you can load into Sound Forge or a similar audio
editing package for closer inspection without relying on your output buffers
and playback code to work properly.

  -- john
  RAD Game Tools
    -----Original Message-----
    From: speex-dev-bounces at xiph.org [mailto:speex-dev-bounces at xiph.org]On
Behalf Of Carine Liang
    Sent: Wednesday, November 01, 2006 9:40 PM
    To: speex-dev at xiph.org
    Subject: Re: [Speex-dev] Integrating speex with VideoNet application:
Constantbackground noise


    Can someone please help me with my problem below. Any suggestions is


    ----- Original Message ----
    From: Carine Liang <carineliang at yahoo.com.sg>
    To: speex-dev at xiph.org; speex-dev at xiph.org
    Sent: Tuesday, 31 October 2006 1:05:49 PM
    Subject: [Speex-dev] Integrating speex with VideoNet application:
Constant background noise


    I am developing a peer-to-peer video conference application which uses
speex as a codec for the voice.

    I am new to speex, so please bear with me if I asked the obvious. After
I added the encode and decode function to my MFC app, I heard a constant
background noise, even when no one is speaking into the microphone.

    #define FRAME_SIZE 160

    The application is coded in MFC C++. The record buffer is set to be the
same as the FRAME_SIZE such that my callback function is called everytime
160 bytes of data is recorded.

    Here's what I did in the initialisation (called only once).
    m_waveFormatEx.wFormatTag =WAVE_FORMAT_PCM;
    m_waveFormatEx.nChannels =1;
    m_waveFormatEx.wBitsPerSample =8;
    m_waveFormatEx.cbSize =0;
    m_waveFormatEx.nSamplesPerSec = 8000;
    m_waveFormatEx.nBlockAlign =1;
    m_waveFormatEx.nAvgBytesPerSec = 8000;

    int quality =8;
    enc_state = speex_encoder_init(&speex_nb_mode);
    speex_encoder_ctl(enc_state, SPEEX_SET_QUALITY, &quality);

    In my recording callback function
    LRESULT RecordSound::OnSoundData(WPARAM wParam, LPARAM lParam)
        dataPtr = (char *)lpHdr ->lpData;
        dataSize = (int)lpHdr ->dwBytesRecorded;

        for(int k=0;k<FRAME_SIZE;k++)
           input[k] = dataPtr[k];     //input is float[FRAME_SIZE]

        speex_encode(enc_state, input, &bits);
        encByte = speex_bits_write(&bits, cbits, 200);

        //send cbits to peer computer via sockets

    In the receiver's initialization function, I've initialized the
    dec_state = speex_decoder_init(&speex_nb_mode);

    In the receiver's socket function, it reads from socket and store the
data in cbits (char array).
        speex_bits_read_from(&bits, cbits, retvalue); //retvalue is 38
        speex_decode(dec_state, &bits, output); //where output is float

        for(int k=0;k<FRAME_SIZE;k++)
           out[k] = output[k];  //out is a char array

       PostThreadMessage( WM_PLAYSOUND_PLAYBLOCK, FRAME_SIZE, (LPARAM)out );

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