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 Libav.
9 *
10 * Libav 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 * Libav 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 Libav; 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 "libavutil/avassert.h"
26#include "libavutil/opt.h"
27#include "avcodec.h"
28#include "internal.h"
29#include "get_bits.h"
30#include "put_bits.h"
31
32/**
33 * G.726 11bit float.
34 * G.726 Standard uses rather odd 11bit floating point arithmentic for
35 * numerous occasions. It's a mistery to me why they did it this way
36 * instead of simply using 32bit integer arithmetic.
37 */
38typedef struct Float11 {
39    uint8_t sign;   /**< 1bit sign */
40    uint8_t exp;    /**< 4bit exponent */
41    uint8_t mant;   /**< 6bit mantissa */
42} Float11;
43
44static inline Float11* i2f(int i, Float11* f)
45{
46    f->sign = (i < 0);
47    if (f->sign)
48        i = -i;
49    f->exp = av_log2_16bit(i) + !!i;
50    f->mant = i? (i<<6) >> f->exp : 1<<5;
51    return f;
52}
53
54static inline int16_t mult(Float11* f1, Float11* f2)
55{
56        int res, exp;
57
58        exp = f1->exp + f2->exp;
59        res = (((f1->mant * f2->mant) + 0x30) >> 4);
60        res = exp > 19 ? res << (exp - 19) : res >> (19 - exp);
61        return (f1->sign ^ f2->sign) ? -res : res;
62}
63
64static inline int sgn(int value)
65{
66    return (value < 0) ? -1 : 1;
67}
68
69typedef struct G726Tables {
70    const int* quant;         /**< quantization table */
71    const int16_t* iquant;    /**< inverse quantization table */
72    const int16_t* W;         /**< special table #1 ;-) */
73    const uint8_t* F;         /**< special table #2 */
74} G726Tables;
75
76typedef struct G726Context {
77    AVClass *class;
78    AVFrame frame;
79    G726Tables tbls;    /**< static tables needed for computation */
80
81    Float11 sr[2];      /**< prev. reconstructed samples */
82    Float11 dq[6];      /**< prev. difference */
83    int a[2];           /**< second order predictor coeffs */
84    int b[6];           /**< sixth order predictor coeffs */
85    int pk[2];          /**< signs of prev. 2 sez + dq */
86
87    int ap;             /**< scale factor control */
88    int yu;             /**< fast scale factor */
89    int yl;             /**< slow scale factor */
90    int dms;            /**< short average magnitude of F[i] */
91    int dml;            /**< long average magnitude of F[i] */
92    int td;             /**< tone detect */
93
94    int se;             /**< estimated signal for the next iteration */
95    int sez;            /**< estimated second order prediction */
96    int y;              /**< quantizer scaling factor for the next iteration */
97    int code_size;
98} G726Context;
99
100static const int quant_tbl16[] =                  /**< 16kbit/s 2bits per sample */
101           { 260, INT_MAX };
102static const int16_t iquant_tbl16[] =
103           { 116, 365, 365, 116 };
104static const int16_t W_tbl16[] =
105           { -22, 439, 439, -22 };
106static const uint8_t F_tbl16[] =
107           { 0, 7, 7, 0 };
108
109static const int quant_tbl24[] =                  /**< 24kbit/s 3bits per sample */
110           {  7, 217, 330, INT_MAX };
111static const int16_t iquant_tbl24[] =
112           { INT16_MIN, 135, 273, 373, 373, 273, 135, INT16_MIN };
113static const int16_t W_tbl24[] =
114           { -4,  30, 137, 582, 582, 137,  30, -4 };
115static const uint8_t F_tbl24[] =
116           { 0, 1, 2, 7, 7, 2, 1, 0 };
117
118static const int quant_tbl32[] =                  /**< 32kbit/s 4bits per sample */
119           { -125,  79, 177, 245, 299, 348, 399, INT_MAX };
120static const int16_t iquant_tbl32[] =
121         { INT16_MIN,   4, 135, 213, 273, 323, 373, 425,
122                 425, 373, 323, 273, 213, 135,   4, INT16_MIN };
123static const int16_t W_tbl32[] =
124           { -12,  18,  41,  64, 112, 198, 355, 1122,
125            1122, 355, 198, 112,  64,  41,  18, -12};
126static const uint8_t F_tbl32[] =
127           { 0, 0, 0, 1, 1, 1, 3, 7, 7, 3, 1, 1, 1, 0, 0, 0 };
128
129static const int quant_tbl40[] =                  /**< 40kbit/s 5bits per sample */
130           { -122, -16,  67, 138, 197, 249, 297, 338,
131              377, 412, 444, 474, 501, 527, 552, INT_MAX };
132static const int16_t iquant_tbl40[] =
133         { INT16_MIN, -66,  28, 104, 169, 224, 274, 318,
134                 358, 395, 429, 459, 488, 514, 539, 566,
135                 566, 539, 514, 488, 459, 429, 395, 358,
136                 318, 274, 224, 169, 104,  28, -66, INT16_MIN };
137static const int16_t W_tbl40[] =
138           {   14,  14,  24,  39,  40,  41,   58,  100,
139              141, 179, 219, 280, 358, 440,  529,  696,
140              696, 529, 440, 358, 280, 219,  179,  141,
141              100,  58,  41,  40,  39,  24,   14,   14 };
142static const uint8_t F_tbl40[] =
143           { 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 2, 3, 4, 5, 6, 6,
144             6, 6, 5, 4, 3, 2, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0 };
145
146static const G726Tables G726Tables_pool[] =
147           {{ quant_tbl16, iquant_tbl16, W_tbl16, F_tbl16 },
148            { quant_tbl24, iquant_tbl24, W_tbl24, F_tbl24 },
149            { quant_tbl32, iquant_tbl32, W_tbl32, F_tbl32 },
150            { quant_tbl40, iquant_tbl40, W_tbl40, F_tbl40 }};
151
152
153/**
154 * Para 4.2.2 page 18: Adaptive quantizer.
155 */
156static inline uint8_t quant(G726Context* c, int d)
157{
158    int sign, exp, i, dln;
159
160    sign = i = 0;
161    if (d < 0) {
162        sign = 1;
163        d = -d;
164    }
165    exp = av_log2_16bit(d);
166    dln = ((exp<<7) + (((d<<7)>>exp)&0x7f)) - (c->y>>2);
167
168    while (c->tbls.quant[i] < INT_MAX && c->tbls.quant[i] < dln)
169        ++i;
170
171    if (sign)
172        i = ~i;
173    if (c->code_size != 2 && i == 0) /* I'm not sure this is a good idea */
174        i = 0xff;
175
176    return i;
177}
178
179/**
180 * Para 4.2.3 page 22: Inverse adaptive quantizer.
181 */
182static inline int16_t inverse_quant(G726Context* c, int i)
183{
184    int dql, dex, dqt;
185
186    dql = c->tbls.iquant[i] + (c->y >> 2);
187    dex = (dql>>7) & 0xf;        /* 4bit exponent */
188    dqt = (1<<7) + (dql & 0x7f); /* log2 -> linear */
189    return (dql < 0) ? 0 : ((dqt<<dex) >> 7);
190}
191
192static int16_t g726_decode(G726Context* c, int I)
193{
194    int dq, re_signal, pk0, fa1, i, tr, ylint, ylfrac, thr2, al, dq0;
195    Float11 f;
196    int I_sig= I >> (c->code_size - 1);
197
198    dq = inverse_quant(c, I);
199
200    /* Transition detect */
201    ylint = (c->yl >> 15);
202    ylfrac = (c->yl >> 10) & 0x1f;
203    thr2 = (ylint > 9) ? 0x1f << 10 : (0x20 + ylfrac) << ylint;
204    tr= (c->td == 1 && dq > ((3*thr2)>>2));
205
206    if (I_sig)  /* get the sign */
207        dq = -dq;
208    re_signal = c->se + dq;
209
210    /* Update second order predictor coefficient A2 and A1 */
211    pk0 = (c->sez + dq) ? sgn(c->sez + dq) : 0;
212    dq0 = dq ? sgn(dq) : 0;
213    if (tr) {
214        c->a[0] = 0;
215        c->a[1] = 0;
216        for (i=0; i<6; i++)
217            c->b[i] = 0;
218    } else {
219        /* This is a bit crazy, but it really is +255 not +256 */
220        fa1 = av_clip((-c->a[0]*c->pk[0]*pk0)>>5, -256, 255);
221
222        c->a[1] += 128*pk0*c->pk[1] + fa1 - (c->a[1]>>7);
223        c->a[1] = av_clip(c->a[1], -12288, 12288);
224        c->a[0] += 64*3*pk0*c->pk[0] - (c->a[0] >> 8);
225        c->a[0] = av_clip(c->a[0], -(15360 - c->a[1]), 15360 - c->a[1]);
226
227        for (i=0; i<6; i++)
228            c->b[i] += 128*dq0*sgn(-c->dq[i].sign) - (c->b[i]>>8);
229    }
230
231    /* Update Dq and Sr and Pk */
232    c->pk[1] = c->pk[0];
233    c->pk[0] = pk0 ? pk0 : 1;
234    c->sr[1] = c->sr[0];
235    i2f(re_signal, &c->sr[0]);
236    for (i=5; i>0; i--)
237        c->dq[i] = c->dq[i-1];
238    i2f(dq, &c->dq[0]);
239    c->dq[0].sign = I_sig; /* Isn't it crazy ?!?! */
240
241    c->td = c->a[1] < -11776;
242
243    /* Update Ap */
244    c->dms += (c->tbls.F[I]<<4) + ((- c->dms) >> 5);
245    c->dml += (c->tbls.F[I]<<4) + ((- c->dml) >> 7);
246    if (tr)
247        c->ap = 256;
248    else {
249        c->ap += (-c->ap) >> 4;
250        if (c->y <= 1535 || c->td || abs((c->dms << 2) - c->dml) >= (c->dml >> 3))
251            c->ap += 0x20;
252    }
253
254    /* Update Yu and Yl */
255    c->yu = av_clip(c->y + c->tbls.W[I] + ((-c->y)>>5), 544, 5120);
256    c->yl += c->yu + ((-c->yl)>>6);
257
258    /* Next iteration for Y */
259    al = (c->ap >= 256) ? 1<<6 : c->ap >> 2;
260    c->y = (c->yl + (c->yu - (c->yl>>6))*al) >> 6;
261
262    /* Next iteration for SE and SEZ */
263    c->se = 0;
264    for (i=0; i<6; i++)
265        c->se += mult(i2f(c->b[i] >> 2, &f), &c->dq[i]);
266    c->sez = c->se >> 1;
267    for (i=0; i<2; i++)
268        c->se += mult(i2f(c->a[i] >> 2, &f), &c->sr[i]);
269    c->se >>= 1;
270
271    return av_clip(re_signal << 2, -0xffff, 0xffff);
272}
273
274static av_cold int g726_reset(G726Context *c)
275{
276    int i;
277
278    c->tbls = G726Tables_pool[c->code_size - 2];
279    for (i=0; i<2; i++) {
280        c->sr[i].mant = 1<<5;
281        c->pk[i] = 1;
282    }
283    for (i=0; i<6; i++) {
284        c->dq[i].mant = 1<<5;
285    }
286    c->yu = 544;
287    c->yl = 34816;
288
289    c->y = 544;
290
291    return 0;
292}
293
294#if CONFIG_ADPCM_G726_ENCODER
295static int16_t g726_encode(G726Context* c, int16_t sig)
296{
297    uint8_t i;
298
299    i = quant(c, sig/4 - c->se) & ((1<<c->code_size) - 1);
300    g726_decode(c, i);
301    return i;
302}
303
304/* Interfacing to the libavcodec */
305
306static av_cold int g726_encode_init(AVCodecContext *avctx)
307{
308    G726Context* c = avctx->priv_data;
309
310    if (avctx->strict_std_compliance > FF_COMPLIANCE_UNOFFICIAL &&
311        avctx->sample_rate != 8000) {
312        av_log(avctx, AV_LOG_ERROR, "Sample rates other than 8kHz are not "
313               "allowed when the compliance level is higher than unofficial. "
314               "Resample or reduce the compliance level.\n");
315        return AVERROR(EINVAL);
316    }
317    av_assert0(avctx->sample_rate > 0);
318
319    if(avctx->channels != 1){
320        av_log(avctx, AV_LOG_ERROR, "Only mono is supported\n");
321        return AVERROR(EINVAL);
322    }
323
324    if (avctx->bit_rate)
325        c->code_size = (avctx->bit_rate + avctx->sample_rate/2) / avctx->sample_rate;
326
327    c->code_size = av_clip(c->code_size, 2, 5);
328    avctx->bit_rate = c->code_size * avctx->sample_rate;
329    avctx->bits_per_coded_sample = c->code_size;
330
331    g726_reset(c);
332
333    avctx->coded_frame = avcodec_alloc_frame();
334    if (!avctx->coded_frame)
335        return AVERROR(ENOMEM);
336    avctx->coded_frame->key_frame = 1;
337
338    /* select a frame size that will end on a byte boundary and have a size of
339       approximately 1024 bytes */
340    avctx->frame_size = ((int[]){ 4096, 2736, 2048, 1640 })[c->code_size - 2];
341
342    return 0;
343}
344
345static av_cold int g726_encode_close(AVCodecContext *avctx)
346{
347    av_freep(&avctx->coded_frame);
348    return 0;
349}
350
351static int g726_encode_frame(AVCodecContext *avctx,
352                            uint8_t *dst, int buf_size, void *data)
353{
354    G726Context *c = avctx->priv_data;
355    const int16_t *samples = data;
356    PutBitContext pb;
357    int i;
358
359    init_put_bits(&pb, dst, 1024*1024);
360
361    for (i = 0; i < avctx->frame_size; i++)
362        put_bits(&pb, c->code_size, g726_encode(c, *samples++));
363
364    flush_put_bits(&pb);
365
366    return put_bits_count(&pb)>>3;
367}
368
369#define OFFSET(x) offsetof(G726Context, x)
370#define AE AV_OPT_FLAG_AUDIO_PARAM | AV_OPT_FLAG_ENCODING_PARAM
371static const AVOption options[] = {
372    { "code_size", "Bits per code", OFFSET(code_size), AV_OPT_TYPE_INT, { 4 }, 2, 5, AE },
373    { NULL },
374};
375
376static const AVClass class = {
377    .class_name = "g726",
378    .item_name  = av_default_item_name,
379    .option     = options,
380    .version    = LIBAVUTIL_VERSION_INT,
381};
382
383static const AVCodecDefault defaults[] = {
384    { "b", "0" },
385    { NULL },
386};
387
388AVCodec ff_adpcm_g726_encoder = {
389    .name           = "g726",
390    .type           = AVMEDIA_TYPE_AUDIO,
391    .id             = CODEC_ID_ADPCM_G726,
392    .priv_data_size = sizeof(G726Context),
393    .init           = g726_encode_init,
394    .encode         = g726_encode_frame,
395    .close          = g726_encode_close,
396    .capabilities = CODEC_CAP_SMALL_LAST_FRAME,
397    .sample_fmts = (const enum AVSampleFormat[]){AV_SAMPLE_FMT_S16,AV_SAMPLE_FMT_NONE},
398    .long_name = NULL_IF_CONFIG_SMALL("G.726 ADPCM"),
399    .priv_class     = &class,
400    .defaults       = defaults,
401};
402#endif
403
404#if CONFIG_ADPCM_G726_DECODER
405static av_cold int g726_decode_init(AVCodecContext *avctx)
406{
407    G726Context* c = avctx->priv_data;
408
409    if (avctx->strict_std_compliance >= FF_COMPLIANCE_STRICT &&
410        avctx->sample_rate != 8000) {
411        av_log(avctx, AV_LOG_ERROR, "Only 8kHz sample rate is allowed when "
412               "the compliance level is strict. Reduce the compliance level "
413               "if you wish to decode the stream anyway.\n");
414        return AVERROR(EINVAL);
415    }
416
417    if(avctx->channels != 1){
418        av_log(avctx, AV_LOG_ERROR, "Only mono is supported\n");
419        return AVERROR(EINVAL);
420    }
421
422    c->code_size = avctx->bits_per_coded_sample;
423    if (c->code_size < 2 || c->code_size > 5) {
424        av_log(avctx, AV_LOG_ERROR, "Invalid number of bits %d\n", c->code_size);
425        return AVERROR(EINVAL);
426    }
427    g726_reset(c);
428
429    avctx->sample_fmt = AV_SAMPLE_FMT_S16;
430
431    avcodec_get_frame_defaults(&c->frame);
432    avctx->coded_frame = &c->frame;
433
434    return 0;
435}
436
437static int g726_decode_frame(AVCodecContext *avctx, void *data,
438                             int *got_frame_ptr, AVPacket *avpkt)
439{
440    const uint8_t *buf = avpkt->data;
441    int buf_size = avpkt->size;
442    G726Context *c = avctx->priv_data;
443    int16_t *samples;
444    GetBitContext gb;
445    int out_samples, ret;
446
447    out_samples = buf_size * 8 / c->code_size;
448
449    /* get output buffer */
450    c->frame.nb_samples = out_samples;
451    if ((ret = avctx->get_buffer(avctx, &c->frame)) < 0) {
452        av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
453        return ret;
454    }
455    samples = (int16_t *)c->frame.data[0];
456
457    init_get_bits(&gb, buf, buf_size * 8);
458
459    while (out_samples--)
460        *samples++ = g726_decode(c, get_bits(&gb, c->code_size));
461
462    if (get_bits_left(&gb) > 0)
463        av_log(avctx, AV_LOG_ERROR, "Frame invalidly split, missing parser?\n");
464
465    *got_frame_ptr   = 1;
466    *(AVFrame *)data = c->frame;
467
468    return buf_size;
469}
470
471static void g726_decode_flush(AVCodecContext *avctx)
472{
473    G726Context *c = avctx->priv_data;
474    g726_reset(c);
475}
476
477AVCodec ff_adpcm_g726_decoder = {
478    .name           = "g726",
479    .type           = AVMEDIA_TYPE_AUDIO,
480    .id             = CODEC_ID_ADPCM_G726,
481    .priv_data_size = sizeof(G726Context),
482    .init           = g726_decode_init,
483    .decode         = g726_decode_frame,
484    .flush          = g726_decode_flush,
485    .capabilities   = CODEC_CAP_DR1,
486    .long_name = NULL_IF_CONFIG_SMALL("G.726 ADPCM"),
487};
488#endif
489