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
35
36 #define ROUND_STANDARD 0.4054f
37 #define ROUND_TO_ZERO 0.1054f
38 #define C_QUANT 0.4054f
39
41 {
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 {
54 }
55
56 static inline float find_max_val(
int group_len,
int swb_size,
const float *scaled)
57 {
58 float maxval = 0.0f;
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
69 {
72 qmaxval = maxval * Q34 +
C_QUANT;
75 else
78 }
79
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;
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]);
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 */
100 nzl += 1.0f;
101 } else {
103 nzl += (
s / ethresh) * (
s / ethresh);
104 else
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);
123 }
124 }
127 } else {
128 return 1.0f;
129 }
130 }
131
132 /** Return the minimum scalefactor where the quantized coef does not clip. */
134 {
136 }
137
138 /** Return the maximum scalefactor where the quantized coef is not zero. */
140 {
142 }
143
144 /*
145 * Returns the closest possible index to an array of float values, given a value.
146 */
148 {
151 for (
i = 0;
i < num;
i++) {
153 if (
error < quant_min_err) {
154 quant_min_err =
error;
156 }
157 }
159 }
160
161 /**
162 * approximates exp10f(-3.0f*(0.5f + 0.5f * cosf(FFMIN(b,15.5f) / 15.5f)))
163 */
165 {
166 return 0.001f + 0.0035f * (
b*
b*
b) / (15.5
f*15.5
f*15.5
f);
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 */
176 {
177 unsigned char prevband = 0;
179 /** Just a safe default */
180 for (
g = 0;
g < 128;
g++)
182
183 /** Now really navigate the nonzero band chain */
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 */
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 */
209 const uint8_t *nextband, int prev_sf, int band)
210 {
211 return prev_sf >= 0
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 */
223 const uint8_t *nextband, int prev_sf, int new_sf, int band)
224 {
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 */
239 {
240 union {
unsigned u;
int s; } v = { previous_val * 1664525
u + 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 */