1 /*
2  * AC-3 encoder float/fixed template
3  * Copyright (c) 2000 Fabrice Bellard
4  * Copyright (c) 2006-2011 Justin Ruggles <justin.ruggles@gmail.com>
5  * Copyright (c) 2006-2010 Prakash Punnoor <prakash@punnoor.de>
6  *
7  * This file is part of FFmpeg.
8  *
9  * FFmpeg is free software; you can redistribute it and/or
10  * modify it under the terms of the GNU Lesser General Public
11  * License as published by the Free Software Foundation; either
12  * version 2.1 of the License, or (at your option) any later version.
13  *
14  * FFmpeg is distributed in the hope that it will be useful,
15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
17  * Lesser General Public License for more details.
18  *
19  * You should have received a copy of the GNU Lesser General Public
20  * License along with FFmpeg; if not, write to the Free Software
21  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
22  */
23 
24 /**
25  * @file
26  * AC-3 encoder float/fixed template
27  */
28 
29 #include <stdint.h>
30 
31 #include "libavutil/attributes.h"
32 #include "libavutil/internal.h"
33 #include "libavutil/mem_internal.h"
34 
35 #include "audiodsp.h"
36 #include "internal.h"
37 #include "ac3enc.h"
38 #include "eac3enc.h"
39 
40 
allocate_sample_buffers(AC3EncodeContext * s)41 static int allocate_sample_buffers(AC3EncodeContext *s)
42 {
43     int ch;
44 
45     if (!FF_ALLOC_TYPED_ARRAY(s->windowed_samples, AC3_WINDOW_SIZE) ||
46         !FF_ALLOCZ_TYPED_ARRAY(s->planar_samples,  s->channels))
47         return AVERROR(ENOMEM);
48 
49     for (ch = 0; ch < s->channels; ch++) {
50         if (!(s->planar_samples[ch] = av_mallocz((AC3_FRAME_SIZE + AC3_BLOCK_SIZE) *
51                                                   sizeof(**s->planar_samples))))
52             return AVERROR(ENOMEM);
53     }
54     return 0;
55 }
56 
57 
58 /*
59  * Copy input samples.
60  * Channels are reordered from FFmpeg's default order to AC-3 order.
61  */
copy_input_samples(AC3EncodeContext * s,SampleType ** samples)62 static void copy_input_samples(AC3EncodeContext *s, SampleType **samples)
63 {
64     int ch;
65 
66     /* copy and remap input samples */
67     for (ch = 0; ch < s->channels; ch++) {
68         /* copy last 256 samples of previous frame to the start of the current frame */
69         memcpy(&s->planar_samples[ch][0], &s->planar_samples[ch][AC3_BLOCK_SIZE * s->num_blocks],
70                AC3_BLOCK_SIZE * sizeof(s->planar_samples[0][0]));
71 
72         /* copy new samples for current frame */
73         memcpy(&s->planar_samples[ch][AC3_BLOCK_SIZE],
74                samples[s->channel_map[ch]],
75                AC3_BLOCK_SIZE * s->num_blocks * sizeof(s->planar_samples[0][0]));
76     }
77 }
78 
79 
80 /*
81  * Apply the MDCT to input samples to generate frequency coefficients.
82  * This applies the KBD window and normalizes the input to reduce precision
83  * loss due to fixed-point calculations.
84  */
apply_mdct(AC3EncodeContext * s)85 static void apply_mdct(AC3EncodeContext *s)
86 {
87     int blk, ch;
88 
89     for (ch = 0; ch < s->channels; ch++) {
90         for (blk = 0; blk < s->num_blocks; blk++) {
91             AC3Block *block = &s->blocks[blk];
92             const SampleType *input_samples = &s->planar_samples[ch][blk * AC3_BLOCK_SIZE];
93 
94             s->fdsp->vector_fmul(s->windowed_samples, input_samples,
95                                  s->mdct_window, AC3_BLOCK_SIZE);
96             s->fdsp->vector_fmul_reverse(s->windowed_samples + AC3_BLOCK_SIZE,
97                                          &input_samples[AC3_BLOCK_SIZE],
98                                          s->mdct_window, AC3_BLOCK_SIZE);
99 
100             s->mdct.mdct_calc(&s->mdct, block->mdct_coef[ch+1],
101                               s->windowed_samples);
102         }
103     }
104 }
105 
106 
107 /*
108  * Calculate coupling channel and coupling coordinates.
109  */
apply_channel_coupling(AC3EncodeContext * s)110 static void apply_channel_coupling(AC3EncodeContext *s)
111 {
112     LOCAL_ALIGNED_16(CoefType, cpl_coords,      [AC3_MAX_BLOCKS], [AC3_MAX_CHANNELS][16]);
113 #if AC3ENC_FLOAT
114     LOCAL_ALIGNED_16(int32_t, fixed_cpl_coords, [AC3_MAX_BLOCKS], [AC3_MAX_CHANNELS][16]);
115 #else
116     int32_t (*fixed_cpl_coords)[AC3_MAX_CHANNELS][16] = cpl_coords;
117 #endif
118     int av_uninit(blk), ch, bnd, i, j;
119     CoefSumType energy[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][16] = {{{0}}};
120     int cpl_start, num_cpl_coefs;
121 
122     memset(cpl_coords,       0, AC3_MAX_BLOCKS * sizeof(*cpl_coords));
123 #if AC3ENC_FLOAT
124     memset(fixed_cpl_coords, 0, AC3_MAX_BLOCKS * sizeof(*cpl_coords));
125 #endif
126 
127     /* align start to 16-byte boundary. align length to multiple of 32.
128         note: coupling start bin % 4 will always be 1 */
129     cpl_start     = s->start_freq[CPL_CH] - 1;
130     num_cpl_coefs = FFALIGN(s->num_cpl_subbands * 12 + 1, 32);
131     cpl_start     = FFMIN(256, cpl_start + num_cpl_coefs) - num_cpl_coefs;
132 
133     /* calculate coupling channel from fbw channels */
134     for (blk = 0; blk < s->num_blocks; blk++) {
135         AC3Block *block = &s->blocks[blk];
136         CoefType *cpl_coef = &block->mdct_coef[CPL_CH][cpl_start];
137         if (!block->cpl_in_use)
138             continue;
139         memset(cpl_coef, 0, num_cpl_coefs * sizeof(*cpl_coef));
140         for (ch = 1; ch <= s->fbw_channels; ch++) {
141             CoefType *ch_coef = &block->mdct_coef[ch][cpl_start];
142             if (!block->channel_in_cpl[ch])
143                 continue;
144             for (i = 0; i < num_cpl_coefs; i++)
145                 cpl_coef[i] += ch_coef[i];
146         }
147 
148         /* coefficients must be clipped in order to be encoded */
149         clip_coefficients(&s->adsp, cpl_coef, num_cpl_coefs);
150     }
151 
152     /* calculate energy in each band in coupling channel and each fbw channel */
153     /* TODO: possibly use SIMD to speed up energy calculation */
154     bnd = 0;
155     i = s->start_freq[CPL_CH];
156     while (i < s->cpl_end_freq) {
157         int band_size = s->cpl_band_sizes[bnd];
158         for (ch = CPL_CH; ch <= s->fbw_channels; ch++) {
159             for (blk = 0; blk < s->num_blocks; blk++) {
160                 AC3Block *block = &s->blocks[blk];
161                 if (!block->cpl_in_use || (ch > CPL_CH && !block->channel_in_cpl[ch]))
162                     continue;
163                 for (j = 0; j < band_size; j++) {
164                     CoefType v = block->mdct_coef[ch][i+j];
165                     MAC_COEF(energy[blk][ch][bnd], v, v);
166                 }
167             }
168         }
169         i += band_size;
170         bnd++;
171     }
172 
173     /* calculate coupling coordinates for all blocks for all channels */
174     for (blk = 0; blk < s->num_blocks; blk++) {
175         AC3Block *block  = &s->blocks[blk];
176         if (!block->cpl_in_use)
177             continue;
178         for (ch = 1; ch <= s->fbw_channels; ch++) {
179             if (!block->channel_in_cpl[ch])
180                 continue;
181             for (bnd = 0; bnd < s->num_cpl_bands; bnd++) {
182                 cpl_coords[blk][ch][bnd] = calc_cpl_coord(energy[blk][ch][bnd],
183                                                           energy[blk][CPL_CH][bnd]);
184             }
185         }
186     }
187 
188     /* determine which blocks to send new coupling coordinates for */
189     for (blk = 0; blk < s->num_blocks; blk++) {
190         AC3Block *block  = &s->blocks[blk];
191         AC3Block *block0 = blk ? &s->blocks[blk-1] : NULL;
192 
193         memset(block->new_cpl_coords, 0, sizeof(block->new_cpl_coords));
194 
195         if (block->cpl_in_use) {
196             /* send new coordinates if this is the first block, if previous
197              * block did not use coupling but this block does, the channels
198              * using coupling has changed from the previous block, or the
199              * coordinate difference from the last block for any channel is
200              * greater than a threshold value. */
201             if (blk == 0 || !block0->cpl_in_use) {
202                 for (ch = 1; ch <= s->fbw_channels; ch++)
203                     block->new_cpl_coords[ch] = 1;
204             } else {
205                 for (ch = 1; ch <= s->fbw_channels; ch++) {
206                     if (!block->channel_in_cpl[ch])
207                         continue;
208                     if (!block0->channel_in_cpl[ch]) {
209                         block->new_cpl_coords[ch] = 1;
210                     } else {
211                         CoefSumType coord_diff = 0;
212                         for (bnd = 0; bnd < s->num_cpl_bands; bnd++) {
213                             coord_diff += FFABS(cpl_coords[blk-1][ch][bnd] -
214                                                 cpl_coords[blk  ][ch][bnd]);
215                         }
216                         coord_diff /= s->num_cpl_bands;
217                         if (coord_diff > NEW_CPL_COORD_THRESHOLD)
218                             block->new_cpl_coords[ch] = 1;
219                     }
220                 }
221             }
222         }
223     }
224 
225     /* calculate final coupling coordinates, taking into account reusing of
226        coordinates in successive blocks */
227     for (bnd = 0; bnd < s->num_cpl_bands; bnd++) {
228         blk = 0;
229         while (blk < s->num_blocks) {
230             int av_uninit(blk1);
231             AC3Block *block  = &s->blocks[blk];
232 
233             if (!block->cpl_in_use) {
234                 blk++;
235                 continue;
236             }
237 
238             for (ch = 1; ch <= s->fbw_channels; ch++) {
239                 CoefSumType energy_ch, energy_cpl;
240                 if (!block->channel_in_cpl[ch])
241                     continue;
242                 energy_cpl = energy[blk][CPL_CH][bnd];
243                 energy_ch = energy[blk][ch][bnd];
244                 blk1 = blk+1;
245                 while (blk1 < s->num_blocks && !s->blocks[blk1].new_cpl_coords[ch]) {
246                     if (s->blocks[blk1].cpl_in_use) {
247                         energy_cpl += energy[blk1][CPL_CH][bnd];
248                         energy_ch += energy[blk1][ch][bnd];
249                     }
250                     blk1++;
251                 }
252                 cpl_coords[blk][ch][bnd] = calc_cpl_coord(energy_ch, energy_cpl);
253             }
254             blk = blk1;
255         }
256     }
257 
258     /* calculate exponents/mantissas for coupling coordinates */
259     for (blk = 0; blk < s->num_blocks; blk++) {
260         AC3Block *block = &s->blocks[blk];
261         if (!block->cpl_in_use)
262             continue;
263 
264 #if AC3ENC_FLOAT
265         s->ac3dsp.float_to_fixed24(fixed_cpl_coords[blk][1],
266                                    cpl_coords[blk][1],
267                                    s->fbw_channels * 16);
268 #endif
269         s->ac3dsp.extract_exponents(block->cpl_coord_exp[1],
270                                     fixed_cpl_coords[blk][1],
271                                     s->fbw_channels * 16);
272 
273         for (ch = 1; ch <= s->fbw_channels; ch++) {
274             int bnd, min_exp, max_exp, master_exp;
275 
276             if (!block->new_cpl_coords[ch])
277                 continue;
278 
279             /* determine master exponent */
280             min_exp = max_exp = block->cpl_coord_exp[ch][0];
281             for (bnd = 1; bnd < s->num_cpl_bands; bnd++) {
282                 int exp = block->cpl_coord_exp[ch][bnd];
283                 min_exp = FFMIN(exp, min_exp);
284                 max_exp = FFMAX(exp, max_exp);
285             }
286             master_exp = ((max_exp - 15) + 2) / 3;
287             master_exp = FFMAX(master_exp, 0);
288             while (min_exp < master_exp * 3)
289                 master_exp--;
290             for (bnd = 0; bnd < s->num_cpl_bands; bnd++) {
291                 block->cpl_coord_exp[ch][bnd] = av_clip(block->cpl_coord_exp[ch][bnd] -
292                                                         master_exp * 3, 0, 15);
293             }
294             block->cpl_master_exp[ch] = master_exp;
295 
296             /* quantize mantissas */
297             for (bnd = 0; bnd < s->num_cpl_bands; bnd++) {
298                 int cpl_exp  = block->cpl_coord_exp[ch][bnd];
299                 int cpl_mant = (fixed_cpl_coords[blk][ch][bnd] << (5 + cpl_exp + master_exp * 3)) >> 24;
300                 if (cpl_exp == 15)
301                     cpl_mant >>= 1;
302                 else
303                     cpl_mant -= 16;
304 
305                 block->cpl_coord_mant[ch][bnd] = cpl_mant;
306             }
307         }
308     }
309 
310     if (AC3ENC_FLOAT && CONFIG_EAC3_ENCODER && s->eac3)
311         ff_eac3_set_cpl_states(s);
312 }
313 
314 
315 /*
316  * Determine rematrixing flags for each block and band.
317  */
compute_rematrixing_strategy(AC3EncodeContext * s)318 static void compute_rematrixing_strategy(AC3EncodeContext *s)
319 {
320     int nb_coefs;
321     int blk, bnd;
322     AC3Block *block, *block0 = NULL;
323 
324     if (s->channel_mode != AC3_CHMODE_STEREO)
325         return;
326 
327     for (blk = 0; blk < s->num_blocks; blk++) {
328         block = &s->blocks[blk];
329         block->new_rematrixing_strategy = !blk;
330 
331         block->num_rematrixing_bands = 4;
332         if (block->cpl_in_use) {
333             block->num_rematrixing_bands -= (s->start_freq[CPL_CH] <= 61);
334             block->num_rematrixing_bands -= (s->start_freq[CPL_CH] == 37);
335             if (blk && block->num_rematrixing_bands != block0->num_rematrixing_bands)
336                 block->new_rematrixing_strategy = 1;
337         }
338         nb_coefs = FFMIN(block->end_freq[1], block->end_freq[2]);
339 
340         if (!s->rematrixing_enabled) {
341             block0 = block;
342             continue;
343         }
344 
345         for (bnd = 0; bnd < block->num_rematrixing_bands; bnd++) {
346             /* calculate sum of squared coeffs for one band in one block */
347             int start = ff_ac3_rematrix_band_tab[bnd];
348             int end   = FFMIN(nb_coefs, ff_ac3_rematrix_band_tab[bnd+1]);
349             CoefSumType sum[4];
350             sum_square_butterfly(s, sum, block->mdct_coef[1] + start,
351                                  block->mdct_coef[2] + start, end - start);
352 
353             /* compare sums to determine if rematrixing will be used for this band */
354             if (FFMIN(sum[2], sum[3]) < FFMIN(sum[0], sum[1]))
355                 block->rematrixing_flags[bnd] = 1;
356             else
357                 block->rematrixing_flags[bnd] = 0;
358 
359             /* determine if new rematrixing flags will be sent */
360             if (blk &&
361                 block->rematrixing_flags[bnd] != block0->rematrixing_flags[bnd]) {
362                 block->new_rematrixing_strategy = 1;
363             }
364         }
365         block0 = block;
366     }
367 }
368 
369 
AC3_NAME(encode_frame)370 int AC3_NAME(encode_frame)(AVCodecContext *avctx, AVPacket *avpkt,
371                            const AVFrame *frame, int *got_packet_ptr)
372 {
373     AC3EncodeContext *s = avctx->priv_data;
374     int ret;
375 
376     if (s->options.allow_per_frame_metadata) {
377         ret = ff_ac3_validate_metadata(s);
378         if (ret)
379             return ret;
380     }
381 
382     if (s->bit_alloc.sr_code == 1 || (AC3ENC_FLOAT && s->eac3))
383         ff_ac3_adjust_frame_size(s);
384 
385     copy_input_samples(s, (SampleType **)frame->extended_data);
386 
387     apply_mdct(s);
388 
389     s->cpl_on = s->cpl_enabled;
390     ff_ac3_compute_coupling_strategy(s);
391 
392     if (s->cpl_on)
393         apply_channel_coupling(s);
394 
395     compute_rematrixing_strategy(s);
396 
397 #if AC3ENC_FLOAT
398     scale_coefficients(s);
399 #endif
400 
401     return ff_ac3_encode_frame_common_end(avctx, avpkt, frame, got_packet_ptr);
402 }
403