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 "aac.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
40static inline void abs_pow34_v(float *out, const float *in, const int size)
41{
42    int i;
43    for (i = 0; i < size; i++) {
44        float a = fabsf(in[i]);
45        out[i] = sqrtf(a * sqrtf(a));
46    }
47}
48
49static inline float pos_pow34(float a)
50{
51    return sqrtf(a * sqrtf(a));
52}
53
54/**
55 * Quantize one coefficient.
56 * @return absolute value of the quantized coefficient
57 * @see 3GPP TS26.403 5.6.2 "Scalefactor determination"
58 */
59static inline int quant(float coef, const float Q, const float rounding)
60{
61    float a = coef * Q;
62    return sqrtf(a * sqrtf(a)) + rounding;
63}
64
65static inline void quantize_bands(int *out, const float *in, const float *scaled,
66                                  int size, int is_signed, int maxval, const float Q34,
67                                  const float rounding)
68{
69    int i;
70    for (i = 0; i < size; i++) {
71        float qc = scaled[i] * Q34;
72        int tmp = (int)FFMIN(qc + rounding, (float)maxval);
73        if (is_signed && in[i] < 0.0f) {
74            tmp = -tmp;
75        }
76        out[i] = tmp;
77    }
78}
79
80static inline float find_max_val(int group_len, int swb_size, const float *scaled)
81{
82    float maxval = 0.0f;
83    int w2, i;
84    for (w2 = 0; w2 < group_len; w2++) {
85        for (i = 0; i < swb_size; i++) {
86            maxval = FFMAX(maxval, scaled[w2*128+i]);
87        }
88    }
89    return maxval;
90}
91
92static inline int find_min_book(float maxval, int sf)
93{
94    float Q34 = ff_aac_pow34sf_tab[POW_SF2_ZERO - sf + SCALE_ONE_POS - SCALE_DIV_512];
95    int qmaxval, cb;
96    qmaxval = maxval * Q34 + C_QUANT;
97    if (qmaxval >= (FF_ARRAY_ELEMS(aac_maxval_cb)))
98        cb = 11;
99    else
100        cb = aac_maxval_cb[qmaxval];
101    return cb;
102}
103
104static inline float find_form_factor(int group_len, int swb_size, float thresh,
105                                     const float *scaled, float nzslope) {
106    const float iswb_size = 1.0f / swb_size;
107    const float iswb_sizem1 = 1.0f / (swb_size - 1);
108    const float ethresh = thresh;
109    float form = 0.0f, weight = 0.0f;
110    int w2, i;
111    for (w2 = 0; w2 < group_len; w2++) {
112        float e = 0.0f, e2 = 0.0f, var = 0.0f, maxval = 0.0f;
113        float nzl = 0;
114        for (i = 0; i < swb_size; i++) {
115            float s = fabsf(scaled[w2*128+i]);
116            maxval = FFMAX(maxval, s);
117            e += s;
118            e2 += s *= s;
119            /* We really don't want a hard non-zero-line count, since
120             * even below-threshold lines do add up towards band spectral power.
121             * So, fall steeply towards zero, but smoothly
122             */
123            if (s >= ethresh) {
124                nzl += 1.0f;
125            } else {
126                if (nzslope == 2.f)
127                    nzl += (s / ethresh) * (s / ethresh);
128                else
129                    nzl += ff_fast_powf(s / ethresh, nzslope);
130            }
131        }
132        if (e2 > thresh) {
133            float frm;
134            e *= iswb_size;
135
136            /** compute variance */
137            for (i = 0; i < swb_size; i++) {
138                float d = fabsf(scaled[w2*128+i]) - e;
139                var += d*d;
140            }
141            var = sqrtf(var * iswb_sizem1);
142
143            e2 *= iswb_size;
144            frm = e / FFMIN(e+4*var,maxval);
145            form += e2 * sqrtf(frm) / FFMAX(0.5f,nzl);
146            weight += e2;
147        }
148    }
149    if (weight > 0) {
150        return form / weight;
151    } else {
152        return 1.0f;
153    }
154}
155
156/** Return the minimum scalefactor where the quantized coef does not clip. */
157static inline uint8_t coef2minsf(float coef)
158{
159    return av_clip_uint8(log2f(coef)*4 - 69 + SCALE_ONE_POS - SCALE_DIV_512);
160}
161
162/** Return the maximum scalefactor where the quantized coef is not zero. */
163static inline uint8_t coef2maxsf(float coef)
164{
165    return av_clip_uint8(log2f(coef)*4 +  6 + SCALE_ONE_POS - SCALE_DIV_512);
166}
167
168/*
169 * Returns the closest possible index to an array of float values, given a value.
170 */
171static inline int quant_array_idx(const float val, const float *arr, const int num)
172{
173    int i, index = 0;
174    float quant_min_err = INFINITY;
175    for (i = 0; i < num; i++) {
176        float error = (val - arr[i])*(val - arr[i]);
177        if (error < quant_min_err) {
178            quant_min_err = error;
179            index = i;
180        }
181    }
182    return index;
183}
184
185/**
186 * approximates exp10f(-3.0f*(0.5f + 0.5f * cosf(FFMIN(b,15.5f) / 15.5f)))
187 */
188static av_always_inline float bval2bmax(float b)
189{
190    return 0.001f + 0.0035f * (b*b*b) / (15.5f*15.5f*15.5f);
191}
192
193/*
194 * Compute a nextband map to be used with SF delta constraint utilities.
195 * The nextband array should contain 128 elements, and positions that don't
196 * map to valid, nonzero bands of the form w*16+g (with w being the initial
197 * window of the window group, only) are left indetermined.
198 */
199static inline void ff_init_nextband_map(const SingleChannelElement *sce, uint8_t *nextband)
200{
201    unsigned char prevband = 0;
202    int w, g;
203    /** Just a safe default */
204    for (g = 0; g < 128; g++)
205        nextband[g] = g;
206
207    /** Now really navigate the nonzero band chain */
208    for (w = 0; w < sce->ics.num_windows; w += sce->ics.group_len[w]) {
209        for (g = 0; g < sce->ics.num_swb; g++) {
210            if (!sce->zeroes[w*16+g] && sce->band_type[w*16+g] < RESERVED_BT)
211                prevband = nextband[prevband] = w*16+g;
212        }
213    }
214    nextband[prevband] = prevband; /* terminate */
215}
216
217/*
218 * Updates nextband to reflect a removed band (equivalent to
219 * calling ff_init_nextband_map after marking a band as zero)
220 */
221static inline void ff_nextband_remove(uint8_t *nextband, int prevband, int band)
222{
223    nextband[prevband] = nextband[band];
224}
225
226/*
227 * Checks whether the specified band could be removed without inducing
228 * scalefactor delta that violates SF delta encoding constraints.
229 * prev_sf has to be the scalefactor of the previous nonzero, nonspecial
230 * band, in encoding order, or negative if there was no such band.
231 */
232static inline int ff_sfdelta_can_remove_band(const SingleChannelElement *sce,
233    const uint8_t *nextband, int prev_sf, int band)
234{
235    return prev_sf >= 0
236        && sce->sf_idx[nextband[band]] >= (prev_sf - SCALE_MAX_DIFF)
237        && sce->sf_idx[nextband[band]] <= (prev_sf + SCALE_MAX_DIFF);
238}
239
240/*
241 * Checks whether the specified band's scalefactor could be replaced
242 * with another one without violating SF delta encoding constraints.
243 * prev_sf has to be the scalefactor of the previous nonzero, nonsepcial
244 * band, in encoding order, or negative if there was no such band.
245 */
246static inline int ff_sfdelta_can_replace(const SingleChannelElement *sce,
247    const uint8_t *nextband, int prev_sf, int new_sf, int band)
248{
249    return new_sf >= (prev_sf - SCALE_MAX_DIFF)
250        && new_sf <= (prev_sf + SCALE_MAX_DIFF)
251        && sce->sf_idx[nextband[band]] >= (new_sf - SCALE_MAX_DIFF)
252        && sce->sf_idx[nextband[band]] <= (new_sf + SCALE_MAX_DIFF);
253}
254
255/**
256 * linear congruential pseudorandom number generator
257 *
258 * @param   previous_val    pointer to the current state of the generator
259 *
260 * @return  Returns a 32-bit pseudorandom integer
261 */
262static av_always_inline int lcg_random(unsigned previous_val)
263{
264    union { unsigned u; int s; } v = { previous_val * 1664525u + 1013904223 };
265    return v.s;
266}
267
268#define ERROR_IF(cond, ...) \
269    if (cond) { \
270        av_log(avctx, AV_LOG_ERROR, __VA_ARGS__); \
271        return AVERROR(EINVAL); \
272    }
273
274#define WARN_IF(cond, ...) \
275    if (cond) { \
276        av_log(avctx, AV_LOG_WARNING, __VA_ARGS__); \
277    }
278
279#endif /* AVCODEC_AACENC_UTILS_H */
280