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b237248e JR |
1 | /* |

2 | * Copyright (c) 2011 Justin Ruggles | |

3 | * | |

4 | * This file is part of Libav. | |

5 | * | |

6 | * Libav is free software; you can redistribute it and/or | |

7 | * modify it under the terms of the GNU Lesser General Public | |

8 | * License as published by the Free Software Foundation; either | |

9 | * version 2.1 of the License, or (at your option) any later version. | |

10 | * | |

11 | * Libav is distributed in the hope that it will be useful, | |

12 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |

13 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |

14 | * Lesser General Public License for more details. | |

15 | * | |

16 | * You should have received a copy of the GNU Lesser General Public | |

17 | * License along with Libav; if not, write to the Free Software | |

18 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA | |

19 | */ | |

20 | ||

21 | #include "libavutil/mathematics.h" | |

22 | #include "adx.h" | |

23 | ||

24 | void ff_adx_calculate_coeffs(int cutoff, int sample_rate, int bits, int *coeff) | |

25 | { | |

26 | double a, b, c; | |

27 | ||

28 | a = M_SQRT2 - cos(2.0 * M_PI * cutoff / sample_rate); | |

29 | b = M_SQRT2 - 1.0; | |

30 | c = (a - sqrt((a + b) * (a - b))) / b; | |

31 | ||

32 | coeff[0] = lrintf(c * 2.0 * (1 << bits)); | |

33 | coeff[1] = lrintf(-(c * c) * (1 << bits)); | |

34 | } |