libavcodec/aacenc_utils.h

   1 /*
   2  * AAC encoder utilities
   3  * Copyright (C) 2015 Rostislav Pehlivanov
   4  *
   5  * This file is part of FFmpeg.
   6  *
   7  * FFmpeg is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU Lesser General Public
   9  * License as published by the Free Software Foundation; either
  10  * version 2.1 of the License, or (at your option) any later version.
  11  *
  12  * FFmpeg is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15  * Lesser General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU Lesser General Public
  18  * License along with FFmpeg; if not, write to the Free Software
  19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  20  */
  21
  22 /**
  23  * @file
  24  * AAC encoder utilities
  25  * @author Rostislav Pehlivanov ( atomnuker gmail com )
  26  */
  27
  28 #ifndef AVCODEC_AACENC_UTILS_H
  29 #define AVCODEC_AACENC_UTILS_H
  30
  31 #include "libavutil/ffmath.h"
  32 #include "aacenc.h"
  33 #include "aacenctab.h"
  34 #include "aactab.h"
  35
  36 #define ROUND_STANDARD 0.4054f
  37 #define ROUND_TO_ZERO 0.1054f
  38 #define C_QUANT 0.4054f
  39
  40 static inline float pos_pow34(float a)
  41 {
  42     return sqrtf(a * sqrtf(a));
  43 }
  44
  45 /**
  46  * Quantize one coefficient.
  47  * @return absolute value of the quantized coefficient
  48  * @see 3GPP TS26.403 5.6.2 "Scalefactor determination"
  49  */
  50 static inline int quant(float coef, const float Q, const float rounding)
  51 {
  52     float a = coef * Q;
  53     return sqrtf(a * sqrtf(a)) + rounding;
  54 }
  55
  56 static inline float find_max_val(int group_len, int swb_size, const float *scaled)
  57 {
  58     float maxval = 0.0f;
  59     int w2, i;
  60     for (w2 = 0; w2 < group_len; w2++) {
  61         for (i = 0; i < swb_size; i++) {
  62             maxval = FFMAX(maxval, scaled[w2*128+i]);
  63         }
  64     }
  65     return maxval;
  66 }
  67
  68 static inline int find_min_book(float maxval, int sf)
  69 {
  70     float Q34 = ff_aac_pow34sf_tab[POW_SF2_ZERO - sf + SCALE_ONE_POS - SCALE_DIV_512];
  71     int qmaxval, cb;
  72     qmaxval = maxval * Q34 + C_QUANT;
  73     if (qmaxval >= (FF_ARRAY_ELEMS(aac_maxval_cb)))
  74         cb = 11;
  75     else
  76         cb = aac_maxval_cb[qmaxval];
  77     return cb;
  78 }
  79
  80 static inline float find_form_factor(int group_len, int swb_size, float thresh,
  81                                      const float *scaled, float nzslope) {
  82     const float iswb_size = 1.0f / swb_size;
  83     const float iswb_sizem1 = 1.0f / (swb_size - 1);
  84     const float ethresh = thresh;
  85     float form = 0.0f, weight = 0.0f;
  86     int w2, i;
  87     for (w2 = 0; w2 < group_len; w2++) {
  88         float e = 0.0f, e2 = 0.0f, var = 0.0f, maxval = 0.0f;
  89         float nzl = 0;
  90         for (i = 0; i < swb_size; i++) {
  91             float s = fabsf(scaled[w2*128+i]);
  92             maxval = FFMAX(maxval, s);
  93             e += s;
  94             e2 += s *= s;
  95             /* We really don't want a hard non-zero-line count, since
  96              * even below-threshold lines do add up towards band spectral power.
  97              * So, fall steeply towards zero, but smoothly
  98              */
  99             if (s >= ethresh) {
 100                 nzl += 1.0f;
 101             } else {
 102                 if (nzslope == 2.f)
 103                     nzl += (s / ethresh) * (s / ethresh);
 104                 else
 105                     nzl += ff_fast_powf(s / ethresh, nzslope);
 106             }
 107         }
 108         if (e2 > thresh) {
 109             float frm;
 110             e *= iswb_size;
 111
 112             /** compute variance */
 113             for (i = 0; i < swb_size; i++) {
 114                 float d = fabsf(scaled[w2*128+i]) - e;
 115                 var += d*d;
 116             }
 117             var = sqrtf(var * iswb_sizem1);
 118
 119             e2 *= iswb_size;
 120             frm = e / FFMIN(e+4*var,maxval);
 121             form += e2 * sqrtf(frm) / FFMAX(0.5f,nzl);
 122             weight += e2;
 123         }
 124     }
 125     if (weight > 0) {
 126         return form / weight;
 127     } else {
 128         return 1.0f;
 129     }
 130 }
 131
 132 /** Return the minimum scalefactor where the quantized coef does not clip. */
 133 static inline uint8_t coef2minsf(float coef)
 134 {
 135     return av_clip_uint8(log2f(coef)*4 - 69 + SCALE_ONE_POS - SCALE_DIV_512);
 136 }
 137
 138 /** Return the maximum scalefactor where the quantized coef is not zero. */
 139 static inline uint8_t coef2maxsf(float coef)
 140 {
 141     return av_clip_uint8(log2f(coef)*4 +  6 + SCALE_ONE_POS - SCALE_DIV_512);
 142 }
 143
 144 /*
 145  * Returns the closest possible index to an array of float values, given a value.
 146  */
 147 static inline int quant_array_idx(const float val, const float *arr, const int num)
 148 {
 149     int i, index = 0;
 150     float quant_min_err = INFINITY;
 151     for (i = 0; i < num; i++) {
 152         float error = (val - arr[i])*(val - arr[i]);
 153         if (error < quant_min_err) {
 154             quant_min_err = error;
 155             index = i;
 156         }
 157     }
 158     return index;
 159 }
 160
 161 /**
 162  * approximates exp10f(-3.0f*(0.5f + 0.5f * cosf(FFMIN(b,15.5f) / 15.5f)))
 163  */
 164 static av_always_inline float bval2bmax(float b)
 165 {
 166     return 0.001f + 0.0035f * (b*b*b) / (15.5f*15.5f*15.5f);
 167 }
 168
 169 /*
 170  * Compute a nextband map to be used with SF delta constraint utilities.
 171  * The nextband array should contain 128 elements, and positions that don't
 172  * map to valid, nonzero bands of the form w*16+g (with w being the initial
 173  * window of the window group, only) are left indetermined.
 174  */
 175 static inline void ff_init_nextband_map(const SingleChannelElement *sce, uint8_t *nextband)
 176 {
 177     unsigned char prevband = 0;
 178     int w, g;
 179     /** Just a safe default */
 180     for (g = 0; g < 128; g++)
 181         nextband[g] = g;
 182
 183     /** Now really navigate the nonzero band chain */
 184     for (w = 0; w < sce->ics.num_windows; w += sce->ics.group_len[w]) {
 185         for (g = 0; g < sce->ics.num_swb; g++) {
 186             if (!sce->zeroes[w*16+g] && sce->band_type[w*16+g] < RESERVED_BT)
 187                 prevband = nextband[prevband] = w*16+g;
 188         }
 189     }
 190     nextband[prevband] = prevband; /* terminate */
 191 }
 192
 193 /*
 194  * Updates nextband to reflect a removed band (equivalent to
 195  * calling ff_init_nextband_map after marking a band as zero)
 196  */
 197 static inline void ff_nextband_remove(uint8_t *nextband, int prevband, int band)
 198 {
 199     nextband[prevband] = nextband[band];
 200 }
 201
 202 /*
 203  * Checks whether the specified band could be removed without inducing
 204  * scalefactor delta that violates SF delta encoding constraints.
 205  * prev_sf has to be the scalefactor of the previous nonzero, nonspecial
 206  * band, in encoding order, or negative if there was no such band.
 207  */
 208 static inline int ff_sfdelta_can_remove_band(const SingleChannelElement *sce,
 209     const uint8_t *nextband, int prev_sf, int band)
 210 {
 211     return prev_sf >= 0
 212         && sce->sf_idx[nextband[band]] >= (prev_sf - SCALE_MAX_DIFF)
 213         && sce->sf_idx[nextband[band]] <= (prev_sf + SCALE_MAX_DIFF);
 214 }
 215
 216 /*
 217  * Checks whether the specified band's scalefactor could be replaced
 218  * with another one without violating SF delta encoding constraints.
 219  * prev_sf has to be the scalefactor of the previous nonzero, nonsepcial
 220  * band, in encoding order, or negative if there was no such band.
 221  */
 222 static inline int ff_sfdelta_can_replace(const SingleChannelElement *sce,
 223     const uint8_t *nextband, int prev_sf, int new_sf, int band)
 224 {
 225     return new_sf >= (prev_sf - SCALE_MAX_DIFF)
 226         && new_sf <= (prev_sf + SCALE_MAX_DIFF)
 227         && sce->sf_idx[nextband[band]] >= (new_sf - SCALE_MAX_DIFF)
 228         && sce->sf_idx[nextband[band]] <= (new_sf + SCALE_MAX_DIFF);
 229 }
 230
 231 /**
 232  * linear congruential pseudorandom number generator
 233  *
 234  * @param   previous_val    pointer to the current state of the generator
 235  *
 236  * @return  Returns a 32-bit pseudorandom integer
 237  */
 238 static av_always_inline int lcg_random(unsigned previous_val)
 239 {
 240     union { unsigned u; int s; } v = { previous_val * 1664525u + 1013904223 };
 241     return v.s;
 242 }
 243
 244 #define ERROR_IF(cond, ...) \
 245     if (cond) { \
 246         av_log(avctx, AV_LOG_ERROR, __VA_ARGS__); \
 247         return AVERROR(EINVAL); \
 248     }
 249
 250 #define WARN_IF(cond, ...) \
 251     if (cond) { \
 252         av_log(avctx, AV_LOG_WARNING, __VA_ARGS__); \
 253     }
 254
 255 #endif /* AVCODEC_AACENC_UTILS_H */