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 {
45 out[
i] = sqrtf(
a * sqrtf(
a));
46 }
47 }
48
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 */
59 static inline int quant(
float coef,
const float Q,
const float rounding)
60 {
62 return sqrtf(
a * sqrtf(
a)) + rounding;
63 }
64
66 int size,
int is_signed,
int maxval,
const float Q34,
67 const float rounding)
68 {
71 float qc = scaled[
i] * Q34;
73 if (is_signed && in[
i] < 0.0
f) {
75 }
77 }
78 }
79
80 static inline float find_max_val(
int group_len,
int swb_size,
const float *scaled)
81 {
82 float maxval = 0.0f;
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
93 {
96 qmaxval = maxval * Q34 +
C_QUANT;
99 else
102 }
103
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;
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);
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 */
124 nzl += 1.0f;
125 } else {
127 nzl += (
s / ethresh) * (
s / ethresh);
128 else
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;
140 }
141 var = sqrtf(var * iswb_sizem1);
142
143 e2 *= iswb_size;
144 frm = e /
FFMIN(e+4*var,maxval);
147 }
148 }
151 } else {
152 return 1.0f;
153 }
154 }
155
156 /** Return the minimum scalefactor where the quantized coef does not clip. */
158 {
160 }
161
162 /** Return the maximum scalefactor where the quantized coef is not zero. */
164 {
166 }
167
168 /*
169 * Returns the closest possible index to an array of float values, given a value.
170 */
172 {
175 for (
i = 0;
i < num;
i++) {
177 if (
error < quant_min_err) {
178 quant_min_err =
error;
180 }
181 }
183 }
184
185 /**
186 * approximates exp10f(-3.0f*(0.5f + 0.5f * cosf(FFMIN(b,15.5f) / 15.5f)))
187 */
189 {
190 return 0.001f + 0.0035f * (
b*
b*
b) / (15.5
f*15.5
f*15.5
f);
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 */
200 {
201 unsigned char prevband = 0;
203 /** Just a safe default */
204 for (
g = 0;
g < 128;
g++)
206
207 /** Now really navigate the nonzero band chain */
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 */
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 */
233 const uint8_t *nextband, int prev_sf, int band)
234 {
235 return prev_sf >= 0
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 */
247 const uint8_t *nextband, int prev_sf, int new_sf, int band)
248 {
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 */
263 {
264 union {
unsigned u;
int s; } v = { previous_val * 1664525
u + 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 */