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g722dec.c
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1 /*
2  * Copyright (c) CMU 1993 Computer Science, Speech Group
3  * Chengxiang Lu and Alex Hauptmann
4  * Copyright (c) 2005 Steve Underwood <steveu at coppice.org>
5  * Copyright (c) 2009 Kenan Gillet
6  * Copyright (c) 2010 Martin Storsjo
7  *
8  * This file is part of FFmpeg.
9  *
10  * FFmpeg is free software; you can redistribute it and/or
11  * modify it under the terms of the GNU Lesser General Public
12  * License as published by the Free Software Foundation; either
13  * version 2.1 of the License, or (at your option) any later version.
14  *
15  * FFmpeg is distributed in the hope that it will be useful,
16  * but WITHOUT ANY WARRANTY; without even the implied warranty of
17  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
18  * Lesser General Public License for more details.
19  *
20  * You should have received a copy of the GNU Lesser General Public
21  * License along with FFmpeg; if not, write to the Free Software
22  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
23  */
24 
25 /**
26  * @file
27  * G.722 ADPCM audio decoder
28  *
29  * This G.722 decoder is a bit-exact implementation of the ITU G.722
30  * specification for all three specified bitrates - 64000bps, 56000bps
31  * and 48000bps. It passes the ITU tests.
32  *
33  * @note For the 56000bps and 48000bps bitrates, the lowest 1 or 2 bits
34  * respectively of each byte are ignored.
35  */
36 
38 #include "libavutil/opt.h"
39 #include "avcodec.h"
40 #include "get_bits.h"
41 #include "g722.h"
42 #include "internal.h"
43 
44 #define OFFSET(x) offsetof(G722Context, x)
45 #define AD AV_OPT_FLAG_AUDIO_PARAM | AV_OPT_FLAG_DECODING_PARAM
46 static const AVOption options[] = {
47  { "bits_per_codeword", "Bits per G722 codeword", OFFSET(bits_per_codeword), AV_OPT_TYPE_FLAGS, { .i64 = 8 }, 6, 8, AD },
48  { NULL }
49 };
50 
51 static const AVClass g722_decoder_class = {
52  .class_name = "g722 decoder",
53  .item_name = av_default_item_name,
54  .option = options,
55  .version = LIBAVUTIL_VERSION_INT,
56 };
57 
59 {
60  G722Context *c = avctx->priv_data;
61 
62  avctx->channels = 1;
65 
66  c->band[0].scale_factor = 8;
67  c->band[1].scale_factor = 2;
68  c->prev_samples_pos = 22;
69 
71  avctx->coded_frame = &c->frame;
72 
73  return 0;
74 }
75 
76 static const int16_t low_inv_quant5[32] = {
77  -35, -35, -2919, -2195, -1765, -1458, -1219, -1023,
78  -858, -714, -587, -473, -370, -276, -190, -110,
79  2919, 2195, 1765, 1458, 1219, 1023, 858, 714,
80  587, 473, 370, 276, 190, 110, 35, -35
81 };
82 
83 static const int16_t *low_inv_quants[3] = { ff_g722_low_inv_quant6,
86 
87 static int g722_decode_frame(AVCodecContext *avctx, void *data,
88  int *got_frame_ptr, AVPacket *avpkt)
89 {
90  G722Context *c = avctx->priv_data;
91  int16_t *out_buf;
92  int j, ret;
93  const int skip = 8 - c->bits_per_codeword;
94  const int16_t *quantizer_table = low_inv_quants[skip];
95  GetBitContext gb;
96 
97  /* get output buffer */
98  c->frame.nb_samples = avpkt->size * 2;
99  if ((ret = ff_get_buffer(avctx, &c->frame)) < 0) {
100  av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
101  return ret;
102  }
103  out_buf = (int16_t *)c->frame.data[0];
104 
105  init_get_bits(&gb, avpkt->data, avpkt->size * 8);
106 
107  for (j = 0; j < avpkt->size; j++) {
108  int ilow, ihigh, rlow, rhigh, dhigh;
109  int xout1, xout2;
110 
111  ihigh = get_bits(&gb, 2);
112  ilow = get_bits(&gb, 6 - skip);
113  skip_bits(&gb, skip);
114 
115  rlow = av_clip((c->band[0].scale_factor * quantizer_table[ilow] >> 10)
116  + c->band[0].s_predictor, -16384, 16383);
117 
118  ff_g722_update_low_predictor(&c->band[0], ilow >> (2 - skip));
119 
120  dhigh = c->band[1].scale_factor * ff_g722_high_inv_quant[ihigh] >> 10;
121  rhigh = av_clip(dhigh + c->band[1].s_predictor, -16384, 16383);
122 
123  ff_g722_update_high_predictor(&c->band[1], dhigh, ihigh);
124 
125  c->prev_samples[c->prev_samples_pos++] = rlow + rhigh;
126  c->prev_samples[c->prev_samples_pos++] = rlow - rhigh;
128  &xout1, &xout2);
129  *out_buf++ = av_clip_int16(xout1 >> 11);
130  *out_buf++ = av_clip_int16(xout2 >> 11);
132  memmove(c->prev_samples, c->prev_samples + c->prev_samples_pos - 22,
133  22 * sizeof(c->prev_samples[0]));
134  c->prev_samples_pos = 22;
135  }
136  }
137 
138  *got_frame_ptr = 1;
139  *(AVFrame *)data = c->frame;
140 
141  return avpkt->size;
142 }
143 
145  .name = "g722",
146  .type = AVMEDIA_TYPE_AUDIO,
148  .priv_data_size = sizeof(G722Context),
151  .capabilities = CODEC_CAP_DR1,
152  .long_name = NULL_IF_CONFIG_SMALL("G.722 ADPCM"),
153  .priv_class = &g722_decoder_class,
154 };