AudioKaraoke Plugin

[Howling wong]

Hi

Do someone have a paper regarding on the origin of the AudioKaraoke, most importantly on how the following function update_filter(),  is being derived

static void
update_filter (GstAudioVoice * filter, const GstAudioInfo * info)
{
  gfloat A, B, C;
  gint rate;

  if (info) {
    /// return whatever is in the information
    rate = GST_AUDIO_INFO_RATE (info);
  } else {
    /// return from the filter
    rate = GST_AUDIO_FILTER_RATE (filter);
  }

  if (rate == 0)
    return;

  C = exp (-2 * G_PI * filter->filter_width / rate);
  B = -4 * C / (1 + C) * cos (2 * G_PI * filter->filter_band / rate);
  A = sqrt (1 - B * B / (4 * C)) * (1 - C);

  filter->A = A;
  filter->B = B;
  filter->C = C;
  filter->y1 = 0.0;
  filter->y2 = 0.0;
}

Regards
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