Spectrum Analyzer

Sample directory

/cri/pc/samples/criatomex/spectrum_analyzer

Data used in the sample

/cri/common/smpdata/criatomex/

• SampleProject.acf
• AtomCueSheet.acb
• AtomCueSheet.awb
  

Sample description

This is a sample that performs frequency analysis of the audio flowing through the bus.

The spectrum analyzer is created with the criAtomDspSpectra_Create function.
The number of analysis bands can be specified using the configuration structure ( CriAtomDspSpectraConfig ).

To obtain the audio of the bus, 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 shows how to analyze the audio from the bus using 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);
}