FFmpeg: libavcodec/gsmdec_template.c Source File

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gsmdec_template.c

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1 /*

2 * gsm 06.10 decoder

4 *

5 * This file is part of FFmpeg.

6 *

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

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

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

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

11 *

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

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

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

15 * Lesser General Public License for more details.

16 *

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

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

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

20 */

22 /**

23 * @file

24 * GSM decoder

25 */

27 #include "get_bits.h"

28 #include "gsm.h"

29 #include "gsmdec_data.h"

31 static void apcm_dequant_add(GetBitContext *gb, int16_t *dst, const int *frame_bits)

32 {

33 int i, val;

34 int maxidx = get_bits(gb, 6);

35 const int16_t *tab = ff_gsm_dequant_tab[maxidx];

36 for (i = 0; i < 13; i++) {

37 val = get_bits(gb, frame_bits[i]);

38 dst[3 * i] += tab[ff_gsm_requant_tab[frame_bits[i]][val]];

39 }

40 }

42 static inline int gsm_mult(int a, int b)

43 {

44 return (int)(a * (SUINT)b + (1 << 14)) >> 15;

45 }

47 static void long_term_synth(int16_t *dst, int lag, int gain_idx)

48 {

49 int i;

50 const int16_t *src = dst - lag;

51 uint16_t gain = ff_gsm_long_term_gain_tab[gain_idx];

52 for (i = 0; i < 40; i++)

53 dst[i] = gsm_mult(gain, src[i]);

54 }

56 static inline int decode_log_area(int coded, int factor, int offset)

57 {

58 coded <<= 10;

59 coded -= offset;

60 return gsm_mult(coded, factor) * 2;

61 }

63 static av_noinline int get_rrp(int filtered)

64 {

65 int abs = FFABS(filtered);

66 if (abs < 11059) abs <<= 1;

67 else if (abs < 20070) abs += 11059;

68 else abs = (abs >> 2) + 26112;

69 return filtered < 0 ? -abs : abs;

70 }

72 static int filter_value(int in, int rrp[8], int v[9])

73 {

74 int i;

75 for (i = 7; i >= 0; i--) {

76 in -= gsm_mult(rrp[i], v[i]);

77 v[i + 1] = v[i] + gsm_mult(rrp[i], in);

78 }

79 v[0] = in;

80 return in;

81 }

83 static void short_term_synth(GSMContext *ctx, int16_t *dst, const int16_t *src)

84 {

85 int i;

86 int rrp[8];

87 int *lar = ctx->lar[ctx->lar_idx];

88 int *lar_prev = ctx->lar[ctx->lar_idx ^ 1];

89 for (i = 0; i < 8; i++)

90 rrp[i] = get_rrp((lar_prev[i] >> 2) + (lar_prev[i] >> 1) + (lar[i] >> 2));

91 for (i = 0; i < 13; i++)

92 dst[i] = filter_value(src[i], rrp, ctx->v);

94 for (i = 0; i < 8; i++)

95 rrp[i] = get_rrp((lar_prev[i] >> 1) + (lar [i] >> 1));

96 for (i = 13; i < 27; i++)

97 dst[i] = filter_value(src[i], rrp, ctx->v);

99 for (i = 0; i < 8; i++)

100 rrp[i] = get_rrp((lar_prev[i] >> 2) + (lar [i] >> 1) + (lar[i] >> 2));

101 for (i = 27; i < 40; i++)

102 dst[i] = filter_value(src[i], rrp, ctx->v);

103

104 for (i = 0; i < 8; i++)

105 rrp[i] = get_rrp(lar[i]);

106 for (i = 40; i < 160; i++)

107 dst[i] = filter_value(src[i], rrp, ctx->v);

108

109 ctx->lar_idx ^= 1;

110 }

111

112 static int postprocess(int16_t *data, int msr)

113 {

114 int i;

115 for (i = 0; i < 160; i++) {

116 msr = av_clip_int16(data[i] + gsm_mult(msr, 28180));

117 data[i] = av_clip_int16(msr * 2) & ~7;

118 }

119 return msr;

120 }

121

122 static int gsm_decode_block(AVCodecContext *avctx, int16_t *samples,

123 GetBitContext *gb, int mode)

124 {

125 GSMContext *ctx = avctx->priv_data;

126 int i;

127 int16_t *ref_dst = ctx->ref_buf + 120;

128 int *lar = ctx->lar[ctx->lar_idx];

129 lar[0] = decode_log_area(get_bits(gb, 6), 13107, 1 << 15);

130 lar[1] = decode_log_area(get_bits(gb, 6), 13107, 1 << 15);

131 lar[2] = decode_log_area(get_bits(gb, 5), 13107, (1 << 14) + 2048*2);

132 lar[3] = decode_log_area(get_bits(gb, 5), 13107, (1 << 14) - 2560*2);

133 lar[4] = decode_log_area(get_bits(gb, 4), 19223, (1 << 13) + 94*2);

134 lar[5] = decode_log_area(get_bits(gb, 4), 17476, (1 << 13) - 1792*2);

135 lar[6] = decode_log_area(get_bits(gb, 3), 31454, (1 << 12) - 341*2);

136 lar[7] = decode_log_area(get_bits(gb, 3), 29708, (1 << 12) - 1144*2);

137

138 for (i = 0; i < 4; i++) {

139 int lag = get_bits(gb, 7);

140 int gain_idx = get_bits(gb, 2);

141 int offset = get_bits(gb, 2);

142 lag = av_clip(lag, 40, 120);

143 long_term_synth(ref_dst, lag, gain_idx);

144 apcm_dequant_add(gb, ref_dst + offset, ff_gsm_apcm_bits[mode][i]);

145 ref_dst += 40;

146 }

147 memcpy(ctx->ref_buf, ctx->ref_buf + 160, 120 * sizeof(*ctx->ref_buf));

148 short_term_synth(ctx, samples, ctx->ref_buf + 120);

149 // for optimal speed this could be merged with short_term_synth,

150 // not done yet because it is a bit ugly

151 ctx->msr = postprocess(samples, ctx->msr);

152 return 0;

153 }

av_clip

#define av_clip

Definition: common.h:98

#define b

Definition: input.c:41

data

const char data[16]

Definition: mxf.c:148

short_term_synth

static void short_term_synth(GSMContext *ctx, int16_t *dst, const int16_t *src)

Definition: gsmdec_template.c:83

gsmdec_data.h

get_bits

static unsigned int get_bits(GetBitContext *s, int n)

Read 1-25 bits.

Definition: get_bits.h:335

GetBitContext

Definition: get_bits.h:108

tab

static const struct twinvq_data tab

Definition: twinvq_data.h:10345

val

static double val(void *priv, double ch)

Definition: aeval.c:78

av_noinline

#define av_noinline

Definition: attributes.h:72

get_rrp

static av_noinline int get_rrp(int filtered)

Definition: gsmdec_template.c:63

gsm_mult

static int gsm_mult(int a, int b)

Definition: gsmdec_template.c:42

gsm.h

ff_gsm_apcm_bits

const int *const ff_gsm_apcm_bits[][4]

Definition: gsmdec_data.c:117

ctx

AVFormatContext * ctx

Definition: movenc.c:48

get_bits.h

FFABS

#define FFABS(a)

Absolute value, Note, INT_MIN / INT64_MIN result in undefined behavior as they are not representable ...

Definition: common.h:72

av_clip_int16

#define av_clip_int16

Definition: common.h:113

abs

#define abs(x)

Definition: cuda_runtime.h:35

ff_gsm_requant_tab

const uint8_t ff_gsm_requant_tab[4][8]

Definition: gsmdec_data.c:29

filter_value

static int filter_value(int in, int rrp[8], int v[9])

Definition: gsmdec_template.c:72

ff_gsm_long_term_gain_tab

const uint16_t ff_gsm_long_term_gain_tab[4]

Definition: gsmdec_data.c:25

The reader does not expect b to be semantically here and if the code is changed by maybe adding a a division or other the signedness will almost certainly be mistaken To avoid this confusion a new type was SUINT is the C unsigned type but it holds a signed int to use the same example SUINT a

Definition: undefined.txt:41

postprocess

static int postprocess(int16_t *data, int msr)

Definition: gsmdec_template.c:112

offset

it s the only field you need to keep assuming you have a context There is some magic you don t need to care about around this just let it vf offset

Definition: writing_filters.txt:86

#define i(width, name, range_min, range_max)

Definition: cbs_h2645.c:255

gsm_decode_block

static int gsm_decode_block(AVCodecContext *avctx, int16_t *samples, GetBitContext *gb, int mode)

Definition: gsmdec_template.c:122