/**
* Convert sample data to different bits per sample.
*
* @param int $bitsPerSample (Required) The new number of bits per sample;
*
* @throws Yop_Poll_WavFileException
*/
public function convertBitsPerSample($bitsPerSample)
{
if ($this->getBitsPerSample() == $bitsPerSample) {
return $this;
}
$tempWav = new Yop_Poll_WavFile($this->getNumChannels(), $this->getSampleRate(), $bitsPerSample);
$tempWav->filter(array(self::FILTER_MIX => $this), 0, $this->getNumBlocks());
$this->setSamples()->setBitsPerSample($bitsPerSample);
// implicit setValidBitsPerSample(), setAudioFormat(), setAudioSubFormat(), setFmtChunkSize(), setFactChunkSize(), setSize(), setActualSize(), setDataOffset(), setByteRate(), setBlockAlign(), setNumBlocks()
$this->_samples = $tempWav->_samples;
$this->setDataSize();
// implicit setSize(), setActualSize(), setNumBlocks()
return $this;
}
/**
* Generate a wav file given the $letters in the code
* @todo Add ability to merge 2 sound files together to have random background sounds
* @param array $letters
* @return string The binary contents of the wav file
*/
protected function generateWAV($letters)
{
$wavCaptcha = new Yop_Poll_WavFile();
$first = true;
// reading first wav file
foreach ($letters as $letter) {
$letter = strtoupper($letter);
try {
$l = new Yop_Poll_WavFile($this->audio_path . '/' . $letter . '.wav');
if ($first) {
// set sample rate, bits/sample, and # of channels for file based on first letter
$wavCaptcha->setSampleRate($l->getSampleRate())->setBitsPerSample($l->getBitsPerSample())->setNumChannels($l->getNumChannels());
$first = false;
}
// append letter to the captcha audio
$wavCaptcha->appendWav($l);
// random length of silence between $audio_gap_min and $audio_gap_max
if ($this->audio_gap_max > 0 && $this->audio_gap_max > $this->audio_gap_min) {
$wavCaptcha->insertSilence(mt_rand($this->audio_gap_min, $this->audio_gap_max) / 1000.0);
}
} catch (Exception $ex) {
// failed to open file, or the wav file is broken or not supported
// 2 wav files were not compatible, different # channels, bits/sample, or sample rate
throw $ex;
}
}
/********* Set up audio filters *****************************/
$filters = array();
if ($this->audio_use_noise == true) {
// use background audio - find random file
$noiseFile = $this->getRandomNoiseFile();
if ($noiseFile !== false && is_readable($noiseFile)) {
try {
$wavNoise = new Yop_Poll_WavFile($noiseFile, false);
} catch (Exception $ex) {
throw $ex;
}
// start at a random offset from the beginning of the Yop_Poll_WavFile
// in order to add more randomness
$randOffset = 0;
if ($wavNoise->getNumBlocks() > 2 * $wavCaptcha->getNumBlocks()) {
$randBlock = rand(0, $wavNoise->getNumBlocks() - $wavCaptcha->getNumBlocks());
$wavNoise->readWavData($randBlock * $wavNoise->getBlockAlign(), $wavCaptcha->getNumBlocks() * $wavNoise->getBlockAlign());
} else {
$wavNoise->readWavData();
$randOffset = rand(0, $wavNoise->getNumBlocks() - 1);
}
$mixOpts = array('wav' => $wavNoise, 'loop' => true, 'blockOffset' => $randOffset);
$filters[Yop_Poll_WavFile::FILTER_MIX] = $mixOpts;
$filters[Yop_Poll_WavFile::FILTER_NORMALIZE] = $this->audio_mix_normalization;
}
}
if ($this->degrade_audio == true) {
// add random noise.
// any noise level below 95% is intensely distorted and not pleasant to the ear
$filters[Yop_Poll_WavFile::FILTER_DEGRADE] = rand(95, 98) / 100.0;
}
if (!empty($filters)) {
$wavCaptcha->filter($filters);
// apply filters to captcha audio
}
return $wavCaptcha->__toString();
}