/*

  * G.726 ADPCM audio codec

  * Copyright (c) 2004 Roman Shaposhnik

  *
  * This is a very straightforward rendition of the G.726

  * Section 4 "Computational Details".

  *

  * This file is part of FFmpeg.
  *
  * FFmpeg is free software; you can redistribute it and/or

  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either

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

  *

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

  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Lesser General Public License for more details.
  *
  * You should have received a copy of the GNU Lesser General Public

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

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

  */
 #include <limits.h>
 #include "avcodec.h"

 #include "bitstream.h"

 /**
  * G.726 11bit float.

  * G.726 Standard uses rather odd 11bit floating point arithmentic for

  * numerous occasions. It's a mistery to me why they did it this way
  * instead of simply using 32bit integer arithmetic.
  */
 typedef struct Float11 {

     uint8_t sign;   /**< 1bit sign */
     uint8_t exp;    /**< 4bit exponent */
     uint8_t mant;   /**< 6bit mantissa */

 } Float11;
 

 static inline Float11* i2f(int i, Float11* f)

 {

     f->sign = (i < 0);
     if (f->sign)
         i = -i;
     f->exp = av_log2_16bit(i) + !!i;
     f->mant = i? (i<<6) >> f->exp : 1<<5;
     return f;

 }
 
 static inline int16_t mult(Float11* f1, Float11* f2)
 {

         int res, exp;

         exp = f1->exp + f2->exp;

         res = (((f1->mant * f2->mant) + 0x30) >> 4);
         res = exp > 19 ? res << (exp - 19) : res >> (19 - exp);

         return (f1->sign ^ f2->sign) ? -res : res;

 }
 
 static inline int sgn(int value)
 {

     return (value < 0) ? -1 : 1;

 }
 
 typedef struct G726Tables {

     const int* quant;         /**< quantization table */

     const int16_t* iquant;    /**< inverse quantization table */

     const int16_t* W;         /**< special table #1 ;-) */
     const uint8_t* F;         /**< special table #2 */

 } G726Tables;
 
 typedef struct G726Context {

     G726Tables tbls;    /**< static tables needed for computation */

 
     Float11 sr[2];      /**< prev. reconstructed samples */
     Float11 dq[6];      /**< prev. difference */
     int a[2];           /**< second order predictor coeffs */
     int b[6];           /**< sixth order predictor coeffs */
     int pk[2];          /**< signs of prev. 2 sez + dq */
 
     int ap;             /**< scale factor control */
     int yu;             /**< fast scale factor */
     int yl;             /**< slow scale factor */
     int dms;            /**< short average magnitude of F[i] */
     int dml;            /**< long average magnitude of F[i] */
     int td;             /**< tone detect */
 
     int se;             /**< estimated signal for the next iteration */
     int sez;            /**< estimated second order prediction */
     int y;              /**< quantizer scaling factor for the next iteration */

     int code_size;

 } G726Context;
 

 static const int quant_tbl16[] =                  /**< 16kbit/s 2bits per sample */

            { 260, INT_MAX };

 static const int16_t iquant_tbl16[] =

            { 116, 365, 365, 116 };

 static const int16_t W_tbl16[] =

            { -22, 439, 439, -22 };

 static const uint8_t F_tbl16[] =

            { 0, 7, 7, 0 };

 static const int quant_tbl24[] =                  /**< 24kbit/s 3bits per sample */

            {  7, 217, 330, INT_MAX };

 static const int16_t iquant_tbl24[] =
            { INT16_MIN, 135, 273, 373, 373, 273, 135, INT16_MIN };

 static const int16_t W_tbl24[] =

            { -4,  30, 137, 582, 582, 137,  30, -4 };

 static const uint8_t F_tbl24[] =

            { 0, 1, 2, 7, 7, 2, 1, 0 };

 static const int quant_tbl32[] =                  /**< 32kbit/s 4bits per sample */

            { -125,  79, 177, 245, 299, 348, 399, INT_MAX };

 static const int16_t iquant_tbl32[] =
          { INT16_MIN,   4, 135, 213, 273, 323, 373, 425,
                  425, 373, 323, 273, 213, 135,   4, INT16_MIN };

 static const int16_t W_tbl32[] =

            { -12,  18,  41,  64, 112, 198, 355, 1122,

             1122, 355, 198, 112,  64,  41,  18, -12};

 static const uint8_t F_tbl32[] =

            { 0, 0, 0, 1, 1, 1, 3, 7, 7, 3, 1, 1, 1, 0, 0, 0 };

 static const int quant_tbl40[] =                  /**< 40kbit/s 5bits per sample */

            { -122, -16,  67, 138, 197, 249, 297, 338,

               377, 412, 444, 474, 501, 527, 552, INT_MAX };

 static const int16_t iquant_tbl40[] =
          { INT16_MIN, -66,  28, 104, 169, 224, 274, 318,

                  358, 395, 429, 459, 488, 514, 539, 566,
                  566, 539, 514, 488, 459, 429, 395, 358,

                  318, 274, 224, 169, 104,  28, -66, INT16_MIN };

 static const int16_t W_tbl40[] =

            {   14,  14,  24,  39,  40,  41,   58,  100,

               141, 179, 219, 280, 358, 440,  529,  696,
               696, 529, 440, 358, 280, 219,  179,  141,
               100,  58,  41,  40,  39,  24,   14,   14 };

 static const uint8_t F_tbl40[] =

            { 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 2, 3, 4, 5, 6, 6,

              6, 6, 5, 4, 3, 2, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0 };

 static const G726Tables G726Tables_pool[] =

            {{ quant_tbl16, iquant_tbl16, W_tbl16, F_tbl16 },
             { quant_tbl24, iquant_tbl24, W_tbl24, F_tbl24 },
             { quant_tbl32, iquant_tbl32, W_tbl32, F_tbl32 },
             { quant_tbl40, iquant_tbl40, W_tbl40, F_tbl40 }};

 /**

  * Para 4.2.2 page 18: Adaptive quantizer.

  */
 static inline uint8_t quant(G726Context* c, int d)
 {

     int sign, exp, i, dln;

     sign = i = 0;
     if (d < 0) {
         sign = 1;
         d = -d;
     }
     exp = av_log2_16bit(d);
     dln = ((exp<<7) + (((d<<7)>>exp)&0x7f)) - (c->y>>2);

     while (c->tbls.quant[i] < INT_MAX && c->tbls.quant[i] < dln)

         ++i;

     if (sign)
         i = ~i;

     if (c->code_size != 2 && i == 0) /* I'm not sure this is a good idea */

         i = 0xff;

     return i;

 }
 

 /**

  * Para 4.2.3 page 22: Inverse adaptive quantizer.
  */
 static inline int16_t inverse_quant(G726Context* c, int i)
 {
     int dql, dex, dqt;

     dql = c->tbls.iquant[i] + (c->y >> 2);

     dex = (dql>>7) & 0xf;        /* 4bit exponent */
     dqt = (1<<7) + (dql & 0x7f); /* log2 -> linear */

     return (dql < 0) ? 0 : ((dqt<<dex) >> 7);

 }
 

 static int16_t g726_decode(G726Context* c, int I)

 {
     int dq, re_signal, pk0, fa1, i, tr, ylint, ylfrac, thr2, al, dq0;
     Float11 f;

     int I_sig= I >> (c->code_size - 1);

     dq = inverse_quant(c, I);
 
     /* Transition detect */
     ylint = (c->yl >> 15);
     ylfrac = (c->yl >> 10) & 0x1f;
     thr2 = (ylint > 9) ? 0x1f << 10 : (0x20 + ylfrac) << ylint;

     tr= (c->td == 1 && dq > ((3*thr2)>>2));
 

     if (I_sig)  /* get the sign */

         dq = -dq;
     re_signal = c->se + dq;

     /* Update second order predictor coefficient A2 and A1 */
     pk0 = (c->sez + dq) ? sgn(c->sez + dq) : 0;
     dq0 = dq ? sgn(dq) : 0;
     if (tr) {
         c->a[0] = 0;

         c->a[1] = 0;

         for (i=0; i<6; i++)

             c->b[i] = 0;

     } else {

         /* This is a bit crazy, but it really is +255 not +256 */

         fa1 = av_clip((-c->a[0]*c->pk[0]*pk0)>>5, -256, 255);

         c->a[1] += 128*pk0*c->pk[1] + fa1 - (c->a[1]>>7);

         c->a[1] = av_clip(c->a[1], -12288, 12288);

         c->a[0] += 64*3*pk0*c->pk[0] - (c->a[0] >> 8);

         c->a[0] = av_clip(c->a[0], -(15360 - c->a[1]), 15360 - c->a[1]);

 
         for (i=0; i<6; i++)

             c->b[i] += 128*dq0*sgn(-c->dq[i].sign) - (c->b[i]>>8);

     }
 
     /* Update Dq and Sr and Pk */
     c->pk[1] = c->pk[0];
     c->pk[0] = pk0 ? pk0 : 1;
     c->sr[1] = c->sr[0];
     i2f(re_signal, &c->sr[0]);
     for (i=5; i>0; i--)

         c->dq[i] = c->dq[i-1];

     i2f(dq, &c->dq[0]);

     c->dq[0].sign = I_sig; /* Isn't it crazy ?!?! */

     c->td = c->a[1] < -11776;

     /* Update Ap */

     c->dms += (c->tbls.F[I]<<4) + ((- c->dms) >> 5);
     c->dml += (c->tbls.F[I]<<4) + ((- c->dml) >> 7);

     if (tr)

         c->ap = 256;

     else {

         c->ap += (-c->ap) >> 4;

         if (c->y <= 1535 || c->td || abs((c->dms << 2) - c->dml) >= (c->dml >> 3))
             c->ap += 0x20;
     }

 
     /* Update Yu and Yl */

     c->yu = av_clip(c->y + c->tbls.W[I] + ((-c->y)>>5), 544, 5120);

     c->yl += c->yu + ((-c->yl)>>6);

     /* Next iteration for Y */
     al = (c->ap >= 256) ? 1<<6 : c->ap >> 2;
     c->y = (c->yl + (c->yu - (c->yl>>6))*al) >> 6;

     /* Next iteration for SE and SEZ */
     c->se = 0;
     for (i=0; i<6; i++)

         c->se += mult(i2f(c->b[i] >> 2, &f), &c->dq[i]);

     c->sez = c->se >> 1;
     for (i=0; i<2; i++)

         c->se += mult(i2f(c->a[i] >> 2, &f), &c->sr[i]);

     c->se >>= 1;
 

     return av_clip(re_signal << 2, -0xffff, 0xffff);

 }
 

 static av_cold int g726_reset(G726Context* c, int index)

 {
     int i;
 

     c->tbls = G726Tables_pool[index];

     for (i=0; i<2; i++) {

         c->sr[i].mant = 1<<5;

         c->pk[i] = 1;

     }
     for (i=0; i<6; i++) {

         c->dq[i].mant = 1<<5;

     }
     c->yu = 544;
     c->yl = 34816;
 
     c->y = 544;
 
     return 0;
 }
 

 #if CONFIG_ADPCM_G726_ENCODER

 static int16_t g726_encode(G726Context* c, int16_t sig)
 {

     uint8_t i;

     i = quant(c, sig/4 - c->se) & ((1<<c->code_size) - 1);

     g726_decode(c, i);

     return i;

 }

 #endif

 
 /* Interfacing to the libavcodec */
 

 static av_cold int g726_init(AVCodecContext * avctx)

 {

     G726Context* c = avctx->priv_data;

     unsigned int index;
 
     if (avctx->sample_rate <= 0) {
         av_log(avctx, AV_LOG_ERROR, "Samplerate is invalid\n");
         return -1;
     }
 
     index = (avctx->bit_rate + avctx->sample_rate/2) / avctx->sample_rate - 2;

     if (avctx->bit_rate % avctx->sample_rate && avctx->codec->encode) {
         av_log(avctx, AV_LOG_ERROR, "Bitrate - Samplerate combination is invalid\n");

         return -1;

     }

     if(avctx->channels != 1){
         av_log(avctx, AV_LOG_ERROR, "Only mono is supported\n");
         return -1;
     }

     if(index>3){
         av_log(avctx, AV_LOG_ERROR, "Unsupported number of bits %d\n", index+2);
         return -1;
     }

     g726_reset(c, index);

     c->code_size = index+2;

     avctx->coded_frame = avcodec_alloc_frame();
     if (!avctx->coded_frame)

         return AVERROR(ENOMEM);

     avctx->coded_frame->key_frame = 1;
 

     if (avctx->codec->decode)
         avctx->sample_fmt = SAMPLE_FMT_S16;
 

     return 0;
 }
 

 static av_cold int g726_close(AVCodecContext *avctx)

 {
     av_freep(&avctx->coded_frame);

     return 0;
 }
 

 #if CONFIG_ADPCM_G726_ENCODER

 static int g726_encode_frame(AVCodecContext *avctx,
                             uint8_t *dst, int buf_size, void *data)
 {

     G726Context *c = avctx->priv_data;

     short *samples = data;
     PutBitContext pb;
 
     init_put_bits(&pb, dst, 1024*1024);
 
     for (; buf_size; buf_size--)

         put_bits(&pb, c->code_size, g726_encode(c, *samples++));

 
     flush_put_bits(&pb);
 

     return put_bits_count(&pb)>>3;
 }

 #endif

 
 static int g726_decode_frame(AVCodecContext *avctx,
                              void *data, int *data_size,

                              const uint8_t *buf, int buf_size)

 {

     G726Context *c = avctx->priv_data;

     short *samples = data;

     GetBitContext gb;
 

     init_get_bits(&gb, buf, buf_size * 8);

     while (get_bits_count(&gb) + c->code_size <= buf_size*8)

         *samples++ = g726_decode(c, get_bits(&gb, c->code_size));

     if(buf_size*8 != get_bits_count(&gb))
         av_log(avctx, AV_LOG_ERROR, "Frame invalidly split, missing parser?\n");

     *data_size = (uint8_t*)samples - (uint8_t*)data;
     return buf_size;
 }
 

 #if CONFIG_ADPCM_G726_ENCODER

 AVCodec adpcm_g726_encoder = {
     "g726",
     CODEC_TYPE_AUDIO,
     CODEC_ID_ADPCM_G726,

     sizeof(G726Context),

     g726_init,
     g726_encode_frame,

     g726_close,

     NULL,

     .sample_fmts = (enum SampleFormat[]){SAMPLE_FMT_S16,SAMPLE_FMT_NONE},

     .long_name = NULL_IF_CONFIG_SMALL("G.726 ADPCM"),

 };

 #endif

 
 AVCodec adpcm_g726_decoder = {
     "g726",
     CODEC_TYPE_AUDIO,
     CODEC_ID_ADPCM_G726,

     sizeof(G726Context),

     g726_init,
     NULL,

     g726_close,

     g726_decode_frame,

     .long_name = NULL_IF_CONFIG_SMALL("G.726 ADPCM"),

 };