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