Spectrum Analyzer

Sample Directory

/CRIWARE/SDK/pc/samples/criatomex/spectrum_analyzer

Sample Description

This sample performs a frequency analysis of the sound passing through a bus.

Create a spectrum analyzer with the criAtomDspSpectra_Create function.
You can specify the number of bands for the analysis in the configuration structure (CriAtomDspSpectraConfig).

To acquire the bus sound, register a callback function with criAtomExAsr_SetBusFilterCallback.
This callback function is called from the audio thread every time audio processing is performed.

The following code demonstrates how to analyze sound on a bus with a spectrum analyzer.

void main()
{
    /* Create a spectrum analyzer */
    app_obj->dsp_hn = criAtomDspSpectra_Create(NULL, NULL, 0);
 
    /* Register a bus filter callback */
    /* Note: In the following example, analysis is performed on signals passing through bus 7. */
    criAtomExAsr_SetBusFilterCallback(7, app_filter_callback, NULL, app_obj);
    
    for (;;) {
        /* Get spectral information */
        spectra_ptr = criAtomDspSpectra_GetLevels(app_obj->dsp_hn);
        
        for (i = 0; i < NUM_BANDS; i++) {
            /* Convert the value to decibels */
            decibel = 20.0f * log10f(spectra_ptr[i]);
            
            /* Select the display range */
            /* In the following example, values greater than -96 dB are displayed */
            graph[i] = (CriSint32)(decibel + 96.0f);
        }
        Sleep(10);
    }
}
 
/* Filter callback */
static void app_filter_callback(void *obj, CriAtomPcmFormat format,
    CriSint32 num_channels, CriSint32 num_samples, void *data[])
{
    AppObj *app_obj = (AppObj*)obj;
 
    /* Do nothing when not playing sound */
    if ((num_channels <= 0) || (num_samples <= 0)) {
        criAtomDspSpectra_Reset(app_obj->dsp_hn);
        return;
    }
 
    /* Spectral analysis */
    criAtomDspSpectra_Process(app_obj->dsp_hn, num_channels, num_samples, (CriFloat32 **)data);
}