FFmpeg: libavcodec/g722.c Source File

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g722.c

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1 /*

2 * G.722 ADPCM audio encoder/decoder

3 *

4 * Copyright (c) CMU 1993 Computer Science, Speech Group

5 * Chengxiang Lu and Alex Hauptmann

9 *

10 * This file is part of FFmpeg.

11 *

12 * FFmpeg is free software; you can redistribute it and/or

13 * modify it under the terms of the GNU Lesser General Public

14 * License as published by the Free Software Foundation; either

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

16 *

17 * FFmpeg is distributed in the hope that it will be useful,

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

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

20 * Lesser General Public License for more details.

21 *

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

23 * License along with FFmpeg; if not, write to the Free Software

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

25 */

27 /**

28 * @file

29 * G.722 ADPCM audio codec

30 *

31 * This G.722 decoder is a bit-exact implementation of the ITU G.722

32 * specification for all three specified bitrates - 64000bps, 56000bps

33 * and 48000bps. It passes the ITU tests.

34 *

35 * @note For the 56000bps and 48000bps bitrates, the lowest 1 or 2 bits

36 * respectively of each byte are ignored.

37 */

39 #include "mathops.h"

40 #include "g722.h"

42 static const int8_t sign_lookup[2] = { -1, 1 };

44 static const int16_t inv_log2_table[32] = {

45 2048, 2093, 2139, 2186, 2233, 2282, 2332, 2383,

46 2435, 2489, 2543, 2599, 2656, 2714, 2774, 2834,

47 2896, 2960, 3025, 3091, 3158, 3228, 3298, 3371,

48 3444, 3520, 3597, 3676, 3756, 3838, 3922, 4008

49 };

50 static const int16_t high_log_factor_step[2] = { 798, -214 };

51 const int16_t ff_g722_high_inv_quant[4] = { -926, -202, 926, 202 };

52 /**

53 * low_log_factor_step[index] == wl[rl42[index]]

54 */

55 static const int16_t low_log_factor_step[16] = {

56 -60, 3042, 1198, 538, 334, 172, 58, -30,

57 3042, 1198, 538, 334, 172, 58, -30, -60

58 };

59 const int16_t ff_g722_low_inv_quant4[16] = {

60 0, -2557, -1612, -1121, -786, -530, -323, -150,

61 2557, 1612, 1121, 786, 530, 323, 150, 0

62 };

63 const int16_t ff_g722_low_inv_quant6[64] = {

64 -17, -17, -17, -17, -3101, -2738, -2376, -2088,

65 -1873, -1689, -1535, -1399, -1279, -1170, -1072, -982,

66 -899, -822, -750, -682, -618, -558, -501, -447,

67 -396, -347, -300, -254, -211, -170, -130, -91,

68 3101, 2738, 2376, 2088, 1873, 1689, 1535, 1399,

69 1279, 1170, 1072, 982, 899, 822, 750, 682,

70 618, 558, 501, 447, 396, 347, 300, 254,

71 211, 170, 130, 91, 54, 17, -54, -17

72 };

74 /**

75 * quadrature mirror filter (QMF) coefficients

76 *

77 * ITU-T G.722 Table 11

78 */

79 static const int16_t qmf_coeffs[12] = {

80 3, -11, 12, 32, -210, 951, 3876, -805, 362, -156, 53, -11,

81 };

84 /**

85 * adaptive predictor

86 *

87 * @param cur_diff the dequantized and scaled delta calculated from the

88 * current codeword

89 */

90 static void do_adaptive_prediction(struct G722Band *band, const int cur_diff)

91 {

92 int sg[2], limit, i, cur_qtzd_reconst;

94 const int cur_part_reconst = band->s_zero + cur_diff < 0;

96 sg[0] = sign_lookup[cur_part_reconst != band->part_reconst_mem[0]];

97 sg[1] = sign_lookup[cur_part_reconst == band->part_reconst_mem[1]];

98 band->part_reconst_mem[1] = band->part_reconst_mem[0];

99 band->part_reconst_mem[0] = cur_part_reconst;

100

101 band->pole_mem[1] = av_clip((sg[0] * av_clip(band->pole_mem[0], -8191, 8191) >> 5) +

102 (sg[1] << 7) + (band->pole_mem[1] * 127 >> 7), -12288, 12288);

103

104 limit = 15360 - band->pole_mem[1];

105 band->pole_mem[0] = av_clip(-192 * sg[0] + (band->pole_mem[0] * 255 >> 8), -limit, limit);

106

107

108 if (cur_diff) {

109 for (i = 0; i < 6; i++)

110 band->zero_mem[i] = ((band->zero_mem[i]*255) >> 8) +

111 ((band->diff_mem[i]^cur_diff) < 0 ? -128 : 128);

112 } else

113 for (i = 0; i < 6; i++)

114 band->zero_mem[i] = (band->zero_mem[i]*255) >> 8;

115

116 for (i = 5; i > 0; i--)

117 band->diff_mem[i] = band->diff_mem[i-1];

118 band->diff_mem[0] = av_clip_int16(cur_diff << 1);

119

120 band->s_zero = 0;

121 for (i = 5; i >= 0; i--)

122 band->s_zero += (band->zero_mem[i]*band->diff_mem[i]) >> 15;

123

124

125 cur_qtzd_reconst = av_clip_int16((band->s_predictor + cur_diff) << 1);

126 band->s_predictor = av_clip_int16(band->s_zero +

127 (band->pole_mem[0] * cur_qtzd_reconst >> 15) +

128 (band->pole_mem[1] * band->prev_qtzd_reconst >> 15));

129 band->prev_qtzd_reconst = cur_qtzd_reconst;

130 }

131

132 static inline int linear_scale_factor(const int log_factor)

133 {

134 const int wd1 = inv_log2_table[(log_factor >> 6) & 31];

135 const int shift = log_factor >> 11;

136 return shift < 0 ? wd1 >> -shift : wd1 << shift;

137 }

138

139 void ff_g722_update_low_predictor(struct G722Band *band, const int ilow)

140 {

141 do_adaptive_prediction(band,

142 band->scale_factor * ff_g722_low_inv_quant4[ilow] >> 10);

143

144 // quantizer adaptation

145 band->log_factor = av_clip((band->log_factor * 127 >> 7) +

146 low_log_factor_step[ilow], 0, 18432);

147 band->scale_factor = linear_scale_factor(band->log_factor - (8 << 11));

148 }

149

150 void ff_g722_update_high_predictor(struct G722Band *band, const int dhigh,

151 const int ihigh)

152 {

153 do_adaptive_prediction(band, dhigh);

154

155 // quantizer adaptation

156 band->log_factor = av_clip((band->log_factor * 127 >> 7) +

157 high_log_factor_step[ihigh&1], 0, 22528);

158 band->scale_factor = linear_scale_factor(band->log_factor - (10 << 11));

159 }

160

161 void ff_g722_apply_qmf(const int16_t *prev_samples, int *xout1, int *xout2)

162 {

163 int i;

164

165 *xout1 = 0;

166 *xout2 = 0;

167 for (i = 0; i < 12; i++) {

168 MAC16(*xout2, prev_samples[2*i ], qmf_coeffs[i ]);

169 MAC16(*xout1, prev_samples[2*i+1], qmf_coeffs[11-i]);

170 }

171 }

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