1/*
2 * G.726 ADPCM audio codec
3 * Copyright (c) 2004 Roman Shaposhnik
4 *
5 * This is a very straightforward rendition of the G.726
6 * Section 4 "Computational Details".
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#include <limits.h>
25#include "avcodec.h"
26#include "get_bits.h"
27#include "put_bits.h"
28
29/**
30 * G.726 11bit float.
31 * G.726 Standard uses rather odd 11bit floating point arithmentic for
32 * numerous occasions. It's a mistery to me why they did it this way
33 * instead of simply using 32bit integer arithmetic.
34 */
35typedef struct Float11 {
36    uint8_t sign;   /**< 1bit sign */
37    uint8_t exp;    /**< 4bit exponent */
38    uint8_t mant;   /**< 6bit mantissa */
39} Float11;
40
41static inline Float11* i2f(int i, Float11* f)
42{
43    f->sign = (i < 0);
44    if (f->sign)
45        i = -i;
46    f->exp = av_log2_16bit(i) + !!i;
47    f->mant = i? (i<<6) >> f->exp : 1<<5;
48    return f;
49}
50
51static inline int16_t mult(Float11* f1, Float11* f2)
52{
53        int res, exp;
54
55        exp = f1->exp + f2->exp;
56        res = (((f1->mant * f2->mant) + 0x30) >> 4);
57        res = exp > 19 ? res << (exp - 19) : res >> (19 - exp);
58        return (f1->sign ^ f2->sign) ? -res : res;
59}
60
61static inline int sgn(int value)
62{
63    return (value < 0) ? -1 : 1;
64}
65
66typedef struct G726Tables {
67    const int* quant;         /**< quantization table */
68    const int16_t* iquant;    /**< inverse quantization table */
69    const int16_t* W;         /**< special table #1 ;-) */
70    const uint8_t* F;         /**< special table #2 */
71} G726Tables;
72
73typedef struct G726Context {
74    G726Tables tbls;    /**< static tables needed for computation */
75
76    Float11 sr[2];      /**< prev. reconstructed samples */
77    Float11 dq[6];      /**< prev. difference */
78    int a[2];           /**< second order predictor coeffs */
79    int b[6];           /**< sixth order predictor coeffs */
80    int pk[2];          /**< signs of prev. 2 sez + dq */
81
82    int ap;             /**< scale factor control */
83    int yu;             /**< fast scale factor */
84    int yl;             /**< slow scale factor */
85    int dms;            /**< short average magnitude of F[i] */
86    int dml;            /**< long average magnitude of F[i] */
87    int td;             /**< tone detect */
88
89    int se;             /**< estimated signal for the next iteration */
90    int sez;            /**< estimated second order prediction */
91    int y;              /**< quantizer scaling factor for the next iteration */
92    int code_size;
93} G726Context;
94
95static const int quant_tbl16[] =                  /**< 16kbit/s 2bits per sample */
96           { 260, INT_MAX };
97static const int16_t iquant_tbl16[] =
98           { 116, 365, 365, 116 };
99static const int16_t W_tbl16[] =
100           { -22, 439, 439, -22 };
101static const uint8_t F_tbl16[] =
102           { 0, 7, 7, 0 };
103
104static const int quant_tbl24[] =                  /**< 24kbit/s 3bits per sample */
105           {  7, 217, 330, INT_MAX };
106static const int16_t iquant_tbl24[] =
107           { INT16_MIN, 135, 273, 373, 373, 273, 135, INT16_MIN };
108static const int16_t W_tbl24[] =
109           { -4,  30, 137, 582, 582, 137,  30, -4 };
110static const uint8_t F_tbl24[] =
111           { 0, 1, 2, 7, 7, 2, 1, 0 };
112
113static const int quant_tbl32[] =                  /**< 32kbit/s 4bits per sample */
114           { -125,  79, 177, 245, 299, 348, 399, INT_MAX };
115static const int16_t iquant_tbl32[] =
116         { INT16_MIN,   4, 135, 213, 273, 323, 373, 425,
117                 425, 373, 323, 273, 213, 135,   4, INT16_MIN };
118static const int16_t W_tbl32[] =
119           { -12,  18,  41,  64, 112, 198, 355, 1122,
120            1122, 355, 198, 112,  64,  41,  18, -12};
121static const uint8_t F_tbl32[] =
122           { 0, 0, 0, 1, 1, 1, 3, 7, 7, 3, 1, 1, 1, 0, 0, 0 };
123
124static const int quant_tbl40[] =                  /**< 40kbit/s 5bits per sample */
125           { -122, -16,  67, 138, 197, 249, 297, 338,
126              377, 412, 444, 474, 501, 527, 552, INT_MAX };
127static const int16_t iquant_tbl40[] =
128         { INT16_MIN, -66,  28, 104, 169, 224, 274, 318,
129                 358, 395, 429, 459, 488, 514, 539, 566,
130                 566, 539, 514, 488, 459, 429, 395, 358,
131                 318, 274, 224, 169, 104,  28, -66, INT16_MIN };
132static const int16_t W_tbl40[] =
133           {   14,  14,  24,  39,  40,  41,   58,  100,
134              141, 179, 219, 280, 358, 440,  529,  696,
135              696, 529, 440, 358, 280, 219,  179,  141,
136              100,  58,  41,  40,  39,  24,   14,   14 };
137static const uint8_t F_tbl40[] =
138           { 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 2, 3, 4, 5, 6, 6,
139             6, 6, 5, 4, 3, 2, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0 };
140
141static const G726Tables G726Tables_pool[] =
142           {{ quant_tbl16, iquant_tbl16, W_tbl16, F_tbl16 },
143            { quant_tbl24, iquant_tbl24, W_tbl24, F_tbl24 },
144            { quant_tbl32, iquant_tbl32, W_tbl32, F_tbl32 },
145            { quant_tbl40, iquant_tbl40, W_tbl40, F_tbl40 }};
146
147
148/**
149 * Para 4.2.2 page 18: Adaptive quantizer.
150 */
151static inline uint8_t quant(G726Context* c, int d)
152{
153    int sign, exp, i, dln;
154
155    sign = i = 0;
156    if (d < 0) {
157        sign = 1;
158        d = -d;
159    }
160    exp = av_log2_16bit(d);
161    dln = ((exp<<7) + (((d<<7)>>exp)&0x7f)) - (c->y>>2);
162
163    while (c->tbls.quant[i] < INT_MAX && c->tbls.quant[i] < dln)
164        ++i;
165
166    if (sign)
167        i = ~i;
168    if (c->code_size != 2 && i == 0) /* I'm not sure this is a good idea */
169        i = 0xff;
170
171    return i;
172}
173
174/**
175 * Para 4.2.3 page 22: Inverse adaptive quantizer.
176 */
177static inline int16_t inverse_quant(G726Context* c, int i)
178{
179    int dql, dex, dqt;
180
181    dql = c->tbls.iquant[i] + (c->y >> 2);
182    dex = (dql>>7) & 0xf;        /* 4bit exponent */
183    dqt = (1<<7) + (dql & 0x7f); /* log2 -> linear */
184    return (dql < 0) ? 0 : ((dqt<<dex) >> 7);
185}
186
187static int16_t g726_decode(G726Context* c, int I)
188{
189    int dq, re_signal, pk0, fa1, i, tr, ylint, ylfrac, thr2, al, dq0;
190    Float11 f;
191    int I_sig= I >> (c->code_size - 1);
192
193    dq = inverse_quant(c, I);
194
195    /* Transition detect */
196    ylint = (c->yl >> 15);
197    ylfrac = (c->yl >> 10) & 0x1f;
198    thr2 = (ylint > 9) ? 0x1f << 10 : (0x20 + ylfrac) << ylint;
199    tr= (c->td == 1 && dq > ((3*thr2)>>2));
200
201    if (I_sig)  /* get the sign */
202        dq = -dq;
203    re_signal = c->se + dq;
204
205    /* Update second order predictor coefficient A2 and A1 */
206    pk0 = (c->sez + dq) ? sgn(c->sez + dq) : 0;
207    dq0 = dq ? sgn(dq) : 0;
208    if (tr) {
209        c->a[0] = 0;
210        c->a[1] = 0;
211        for (i=0; i<6; i++)
212            c->b[i] = 0;
213    } else {
214        /* This is a bit crazy, but it really is +255 not +256 */
215        fa1 = av_clip((-c->a[0]*c->pk[0]*pk0)>>5, -256, 255);
216
217        c->a[1] += 128*pk0*c->pk[1] + fa1 - (c->a[1]>>7);
218        c->a[1] = av_clip(c->a[1], -12288, 12288);
219        c->a[0] += 64*3*pk0*c->pk[0] - (c->a[0] >> 8);
220        c->a[0] = av_clip(c->a[0], -(15360 - c->a[1]), 15360 - c->a[1]);
221
222        for (i=0; i<6; i++)
223            c->b[i] += 128*dq0*sgn(-c->dq[i].sign) - (c->b[i]>>8);
224    }
225
226    /* Update Dq and Sr and Pk */
227    c->pk[1] = c->pk[0];
228    c->pk[0] = pk0 ? pk0 : 1;
229    c->sr[1] = c->sr[0];
230    i2f(re_signal, &c->sr[0]);
231    for (i=5; i>0; i--)
232        c->dq[i] = c->dq[i-1];
233    i2f(dq, &c->dq[0]);
234    c->dq[0].sign = I_sig; /* Isn't it crazy ?!?! */
235
236    c->td = c->a[1] < -11776;
237
238    /* Update Ap */
239    c->dms += (c->tbls.F[I]<<4) + ((- c->dms) >> 5);
240    c->dml += (c->tbls.F[I]<<4) + ((- c->dml) >> 7);
241    if (tr)
242        c->ap = 256;
243    else {
244        c->ap += (-c->ap) >> 4;
245        if (c->y <= 1535 || c->td || abs((c->dms << 2) - c->dml) >= (c->dml >> 3))
246            c->ap += 0x20;
247    }
248
249    /* Update Yu and Yl */
250    c->yu = av_clip(c->y + c->tbls.W[I] + ((-c->y)>>5), 544, 5120);
251    c->yl += c->yu + ((-c->yl)>>6);
252
253    /* Next iteration for Y */
254    al = (c->ap >= 256) ? 1<<6 : c->ap >> 2;
255    c->y = (c->yl + (c->yu - (c->yl>>6))*al) >> 6;
256
257    /* Next iteration for SE and SEZ */
258    c->se = 0;
259    for (i=0; i<6; i++)
260        c->se += mult(i2f(c->b[i] >> 2, &f), &c->dq[i]);
261    c->sez = c->se >> 1;
262    for (i=0; i<2; i++)
263        c->se += mult(i2f(c->a[i] >> 2, &f), &c->sr[i]);
264    c->se >>= 1;
265
266    return av_clip(re_signal << 2, -0xffff, 0xffff);
267}
268
269static av_cold int g726_reset(G726Context* c, int index)
270{
271    int i;
272
273    c->tbls = G726Tables_pool[index];
274    for (i=0; i<2; i++) {
275        c->sr[i].mant = 1<<5;
276        c->pk[i] = 1;
277    }
278    for (i=0; i<6; i++) {
279        c->dq[i].mant = 1<<5;
280    }
281    c->yu = 544;
282    c->yl = 34816;
283
284    c->y = 544;
285
286    return 0;
287}
288
289#if CONFIG_ADPCM_G726_ENCODER
290static int16_t g726_encode(G726Context* c, int16_t sig)
291{
292    uint8_t i;
293
294    i = quant(c, sig/4 - c->se) & ((1<<c->code_size) - 1);
295    g726_decode(c, i);
296    return i;
297}
298#endif
299
300/* Interfacing to the libavcodec */
301
302static av_cold int g726_init(AVCodecContext * avctx)
303{
304    G726Context* c = avctx->priv_data;
305    unsigned int index;
306
307    if (avctx->sample_rate <= 0) {
308        av_log(avctx, AV_LOG_ERROR, "Samplerate is invalid\n");
309        return -1;
310    }
311
312    index = (avctx->bit_rate + avctx->sample_rate/2) / avctx->sample_rate - 2;
313
314    if (avctx->bit_rate % avctx->sample_rate && avctx->codec->encode) {
315        av_log(avctx, AV_LOG_ERROR, "Bitrate - Samplerate combination is invalid\n");
316        return -1;
317    }
318    if(avctx->channels != 1){
319        av_log(avctx, AV_LOG_ERROR, "Only mono is supported\n");
320        return -1;
321    }
322    if(index>3){
323        av_log(avctx, AV_LOG_ERROR, "Unsupported number of bits %d\n", index+2);
324        return -1;
325    }
326    g726_reset(c, index);
327    c->code_size = index+2;
328
329    avctx->coded_frame = avcodec_alloc_frame();
330    if (!avctx->coded_frame)
331        return AVERROR(ENOMEM);
332    avctx->coded_frame->key_frame = 1;
333
334    if (avctx->codec->decode)
335        avctx->sample_fmt = SAMPLE_FMT_S16;
336
337    return 0;
338}
339
340static av_cold int g726_close(AVCodecContext *avctx)
341{
342    av_freep(&avctx->coded_frame);
343    return 0;
344}
345
346#if CONFIG_ADPCM_G726_ENCODER
347static int g726_encode_frame(AVCodecContext *avctx,
348                            uint8_t *dst, int buf_size, void *data)
349{
350    G726Context *c = avctx->priv_data;
351    short *samples = data;
352    PutBitContext pb;
353
354    init_put_bits(&pb, dst, 1024*1024);
355
356    for (; buf_size; buf_size--)
357        put_bits(&pb, c->code_size, g726_encode(c, *samples++));
358
359    flush_put_bits(&pb);
360
361    return put_bits_count(&pb)>>3;
362}
363#endif
364
365static int g726_decode_frame(AVCodecContext *avctx,
366                             void *data, int *data_size,
367                             AVPacket *avpkt)
368{
369    const uint8_t *buf = avpkt->data;
370    int buf_size = avpkt->size;
371    G726Context *c = avctx->priv_data;
372    short *samples = data;
373    GetBitContext gb;
374
375    init_get_bits(&gb, buf, buf_size * 8);
376
377    while (get_bits_count(&gb) + c->code_size <= buf_size*8)
378        *samples++ = g726_decode(c, get_bits(&gb, c->code_size));
379
380    if(buf_size*8 != get_bits_count(&gb))
381        av_log(avctx, AV_LOG_ERROR, "Frame invalidly split, missing parser?\n");
382
383    *data_size = (uint8_t*)samples - (uint8_t*)data;
384    return buf_size;
385}
386
387#if CONFIG_ADPCM_G726_ENCODER
388AVCodec adpcm_g726_encoder = {
389    "g726",
390    AVMEDIA_TYPE_AUDIO,
391    CODEC_ID_ADPCM_G726,
392    sizeof(G726Context),
393    g726_init,
394    g726_encode_frame,
395    g726_close,
396    NULL,
397    .sample_fmts = (const enum SampleFormat[]){SAMPLE_FMT_S16,SAMPLE_FMT_NONE},
398    .long_name = NULL_IF_CONFIG_SMALL("G.726 ADPCM"),
399};
400#endif
401
402AVCodec adpcm_g726_decoder = {
403    "g726",
404    AVMEDIA_TYPE_AUDIO,
405    CODEC_ID_ADPCM_G726,
406    sizeof(G726Context),
407    g726_init,
408    NULL,
409    g726_close,
410    g726_decode_frame,
411    .long_name = NULL_IF_CONFIG_SMALL("G.726 ADPCM"),
412};
413