Function detectBPM

lib-src/soundtouch/source/SoundStretch/main.cpp:230–281

Detect BPM rate of inFile and adjust tempo setting accordingly if necessary

// Detect BPM rate of inFile and adjust tempo setting accordingly if necessary
static void detectBPM(WavInFile *inFile, RunParameters *params)
{
    float bpmValue;
    int nChannels;
    BPMDetect bpm(inFile->getNumChannels(), inFile->getSampleRate());
    SAMPLETYPE sampleBuffer[BUFF_SIZE];

    // detect bpm rate
    fprintf(stderr, "Detecting BPM rate...");
    fflush(stderr);

    nChannels = (int)inFile->getNumChannels();
    assert(BUFF_SIZE % nChannels == 0);

    // Process the 'inFile' in small blocks, repeat until whole file has 
    // been processed
    while (inFile->eof() == 0)
    {
        int num, samples;

        // Read sample data from input file
        num = inFile->read(sampleBuffer, BUFF_SIZE);

        // Enter the new samples to the bpm analyzer class
        samples = num / nChannels;
        bpm.inputSamples(sampleBuffer, samples);
    }

    // Now the whole song data has been analyzed. Read the resulting bpm.
    bpmValue = bpm.getBpm();
    fprintf(stderr, "Done!\n");

    // rewind the file after bpm detection
    inFile->rewind();

    if (bpmValue > 0)
    {
        fprintf(stderr, "Detected BPM rate %.1f\n\n", bpmValue);
    }
    else
    {
        fprintf(stderr, "Couldn't detect BPM rate.\n\n");
        return;
    }

    if (params->goalBPM > 0)
    {
        // adjust tempo to given bpm
        params->tempoDelta = (params->goalBPM / bpmValue - 1.0f) * 100.0f;
        fprintf(stderr, "The file will be converted to %.1f BPM\n\n", params->goalBPM);
    }
}