Need Some help with the mp3encoder

hello

i am a newbie to the ipp.   i want to use the IPP to encoder PCM to MP3.

Now we use the lame (lame.sourceforge.net) to do this thing, encoder PCM to MP3.

we want to use the IPP 8.0  to instead of lame.  

PCM  DATA is   8000hz      2channels

so i am tring like this.

    audio_encoder_params = new MP3EncoderParams();

    audio_encoder_params->m_info.audioInfo.m_iChannelMask =  CHANNEL_FRONT_LEFT | CHANNEL_FRONT_RIGHT;
    audio_encoder_params->m_info.audioInfo.m_iSampleFrequency = samplerate;
    audio_encoder_params->m_info.audioInfo.m_iChannels = channels;
    audio_encoder_params->m_info.iBitrate = 128000;
    
    audio_encoder_params->stereo_mode = UMC_MPA_LR_STEREO;
    audio_encoder_params->ns_mode = 0;
    audio_encoder_params->layer = 3;
    audio_encoder_params->force_mpeg1 = 0;
    audio_encoder_params->mc_matrix_procedure = 0;
    audio_encoder_params->mc_lfe_filter_off = 0;
    audio_encoder_params->mode = UMC_MPAENC_CBR;
    
    audio_encoder_params->m_pData = NULL;

    pAudioEncoder = new MP3Encoder();
    if (pAudioEncoder == NULL) {
        switch_log_printf(SWITCH_CHANNEL_LOG, SWITCH_LOG_ERROR, "Can't create audio codec object MP3!\n");
        return SWITCH_STATUS_FALSE;
    }

    sts = pAudioEncoder->Init(audio_encoder_params);
    if (sts != UMC_OK) {
        switch_log_printf(SWITCH_CHANNEL_LOG, SWITCH_LOG_ERROR, "audioCodec Init failed: %d\n", sts);
        return SWITCH_STATUS_FALSE;
    }
    
    sts = pAudioEncoder->GetInfo(audio_encoder_params);
    if (sts < 0) {
        switch_log_printf(SWITCH_CHANNEL_LOG, SWITCH_LOG_ERROR, "audioCodec GetInfo failed\n");
        return SWITCH_STATUS_FALSE;
    }
    
    pOut = new MediaData();
    if (NULL == pOut) {
        switch_log_printf(SWITCH_CHANNEL_LOG, SWITCH_LOG_ERROR, "Memory allocation error\n");
        return SWITCH_STATUS_FALSE;
    }
    
    pOut->Alloc(context->mp3buflen);
    
    pIn = new MediaData();
    if (NULL == pOut) {
        switch_log_printf(SWITCH_CHANNEL_LOG, SWITCH_LOG_ERROR, "Memory allocation error\n");
        return SWITCH_STATUS_FALSE;
    }
    
    pIn->Alloc(nsamples);
    memcpy((void *)pIn->GetBufferPointer(), (void *)audio, nsamples);
    pIn->SetDataSize(nsamples);
    
    log_printf(CHANNEL_LOG, LOG_DEBUG, "Input Data, Size: %d \n", pIn->GetDataSize());
    
    sts = pAudioEncoder->GetFrame(pIn, pOut);
    if (sts == UMC_OK) {
        log_printf(CHANNEL_LOG, LOG_DEBUG, "GetFrame OK, Size: %d \n", pOut->GetDataSize());
    } else {
        log_printf(CHANNEL_LOG, LOG_ERROR, "GetFrame Error: %d\n", sts);
    }
    
    rlen = pOut->GetDataSize();

    if (rlen) {
        int ret = fwrite(pOut->GetBufferPointer(), 1, rlen, fp);
        if (ret < 0) {
            return STATUS_FALSE;
        }
    }

the question is

the data i input size is 16384

the pOut->GetDataSize()  just is 321.

when i use cool edit to view the mp3 file.   it just silence.

pls help me.  thank you very much.