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4349 | Serge | 1 | /* |
2 | * various filters for ACELP-based codecs |
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3 | * |
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4 | * Copyright (c) 2008 Vladimir Voroshilov |
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5 | * |
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6 | * This file is part of FFmpeg. |
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7 | * |
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8 | * FFmpeg is free software; you can redistribute it and/or |
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9 | * modify it under the terms of the GNU Lesser General Public |
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10 | * License as published by the Free Software Foundation; either |
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11 | * version 2.1 of the License, or (at your option) any later version. |
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12 | * |
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13 | * FFmpeg is distributed in the hope that it will be useful, |
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14 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
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15 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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16 | * Lesser General Public License for more details. |
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17 | * |
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18 | * You should have received a copy of the GNU Lesser General Public |
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19 | * License along with FFmpeg; if not, write to the Free Software |
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20 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
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21 | */ |
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22 | |||
23 | #ifndef AVCODEC_ACELP_FILTERS_H |
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24 | #define AVCODEC_ACELP_FILTERS_H |
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25 | |||
26 | #include |
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27 | |||
28 | typedef struct ACELPFContext { |
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29 | /** |
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30 | * Floating point version of ff_acelp_interpolate() |
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31 | */ |
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32 | void (*acelp_interpolatef)(float *out, const float *in, |
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33 | const float *filter_coeffs, int precision, |
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34 | int frac_pos, int filter_length, int length); |
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35 | |||
36 | /** |
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37 | * Apply an order 2 rational transfer function in-place. |
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38 | * |
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39 | * @param out output buffer for filtered speech samples |
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40 | * @param in input buffer containing speech data (may be the same as out) |
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41 | * @param zero_coeffs z^-1 and z^-2 coefficients of the numerator |
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42 | * @param pole_coeffs z^-1 and z^-2 coefficients of the denominator |
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43 | * @param gain scale factor for final output |
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44 | * @param mem intermediate values used by filter (should be 0 initially) |
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45 | * @param n number of samples (should be a multiple of eight) |
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46 | */ |
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47 | void (*acelp_apply_order_2_transfer_function)(float *out, const float *in, |
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48 | const float zero_coeffs[2], |
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49 | const float pole_coeffs[2], |
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50 | float gain, |
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51 | float mem[2], int n); |
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52 | |||
53 | }ACELPFContext; |
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54 | |||
55 | /** |
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56 | * Initialize ACELPFContext. |
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57 | */ |
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58 | void ff_acelp_filter_init(ACELPFContext *c); |
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59 | void ff_acelp_filter_init_mips(ACELPFContext *c); |
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60 | |||
61 | /** |
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62 | * low-pass Finite Impulse Response filter coefficients. |
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63 | * |
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64 | * Hamming windowed sinc filter with cutoff freq 3/40 of the sampling freq, |
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65 | * the coefficients are scaled by 2^15. |
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66 | * This array only contains the right half of the filter. |
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67 | * This filter is likely identical to the one used in G.729, though this |
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68 | * could not be determined from the original comments with certainty. |
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69 | */ |
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70 | extern const int16_t ff_acelp_interp_filter[61]; |
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71 | |||
72 | /** |
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73 | * Generic FIR interpolation routine. |
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74 | * @param[out] out buffer for interpolated data |
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75 | * @param in input data |
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76 | * @param filter_coeffs interpolation filter coefficients (0.15) |
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77 | * @param precision sub sample factor, that is the precision of the position |
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78 | * @param frac_pos fractional part of position [0..precision-1] |
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79 | * @param filter_length filter length |
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80 | * @param length length of output |
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81 | * |
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82 | * filter_coeffs contains coefficients of the right half of the symmetric |
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83 | * interpolation filter. filter_coeffs[0] should the central (unpaired) coefficient. |
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84 | * See ff_acelp_interp_filter for an example. |
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85 | * |
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86 | */ |
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87 | void ff_acelp_interpolate(int16_t* out, const int16_t* in, |
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88 | const int16_t* filter_coeffs, int precision, |
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89 | int frac_pos, int filter_length, int length); |
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90 | |||
91 | /** |
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92 | * Floating point version of ff_acelp_interpolate() |
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93 | */ |
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94 | void ff_acelp_interpolatef(float *out, const float *in, |
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95 | const float *filter_coeffs, int precision, |
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96 | int frac_pos, int filter_length, int length); |
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97 | |||
98 | |||
99 | /** |
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100 | * high-pass filtering and upscaling (4.2.5 of G.729). |
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101 | * @param[out] out output buffer for filtered speech data |
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102 | * @param[in,out] hpf_f past filtered data from previous (2 items long) |
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103 | * frames (-0x20000000 <= (14.13) < 0x20000000) |
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104 | * @param in speech data to process |
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105 | * @param length input data size |
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106 | * |
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107 | * out[i] = 0.93980581 * in[i] - 1.8795834 * in[i-1] + 0.93980581 * in[i-2] + |
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108 | * 1.9330735 * out[i-1] - 0.93589199 * out[i-2] |
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109 | * |
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110 | * The filter has a cut-off frequency of 1/80 of the sampling freq |
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111 | * |
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112 | * @note Two items before the top of the in buffer must contain two items from the |
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113 | * tail of the previous subframe. |
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114 | * |
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115 | * @remark It is safe to pass the same array in in and out parameters. |
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116 | * |
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117 | * @remark AMR uses mostly the same filter (cut-off frequency 60Hz, same formula, |
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118 | * but constants differs in 5th sign after comma). Fortunately in |
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119 | * fixed-point all coefficients are the same as in G.729. Thus this |
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120 | * routine can be used for the fixed-point AMR decoder, too. |
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121 | */ |
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122 | void ff_acelp_high_pass_filter(int16_t* out, int hpf_f[2], |
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123 | const int16_t* in, int length); |
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124 | |||
125 | /** |
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126 | * Apply an order 2 rational transfer function in-place. |
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127 | * |
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128 | * @param out output buffer for filtered speech samples |
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129 | * @param in input buffer containing speech data (may be the same as out) |
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130 | * @param zero_coeffs z^-1 and z^-2 coefficients of the numerator |
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131 | * @param pole_coeffs z^-1 and z^-2 coefficients of the denominator |
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132 | * @param gain scale factor for final output |
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133 | * @param mem intermediate values used by filter (should be 0 initially) |
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134 | * @param n number of samples |
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135 | */ |
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136 | void ff_acelp_apply_order_2_transfer_function(float *out, const float *in, |
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137 | const float zero_coeffs[2], |
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138 | const float pole_coeffs[2], |
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139 | float gain, |
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140 | float mem[2], int n); |
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141 | |||
142 | /** |
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143 | * Apply tilt compensation filter, 1 - tilt * z-1. |
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144 | * |
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145 | * @param mem pointer to the filter's state (one single float) |
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146 | * @param tilt tilt factor |
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147 | * @param samples array where the filter is applied |
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148 | * @param size the size of the samples array |
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149 | */ |
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150 | void ff_tilt_compensation(float *mem, float tilt, float *samples, int size); |
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151 | |||
152 | |||
153 | #endif /* AVCODEC_ACELP_FILTERS_H */>=> |