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>
7 * This file is part of Libav.
9 * Libav 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.
14 * Libav 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.
19 * You should have received a copy of the GNU Lesser General Public
20 * License along with Libav; if not, write to the Free Software
21 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
26 * AC-3 encoder float/fixed template
34 /* prototypes for static functions in ac3enc_fixed.c and ac3enc_float.c */
36 static void scale_coefficients(AC3EncodeContext *s);
38 static void apply_window(DSPContext *dsp, SampleType *output,
39 const SampleType *input, const SampleType *window,
42 static int normalize_samples(AC3EncodeContext *s);
44 static void clip_coefficients(DSPContext *dsp, CoefType *coef, unsigned int len);
47 int AC3_NAME(allocate_sample_buffers)(AC3EncodeContext *s)
51 FF_ALLOC_OR_GOTO(s->avctx, s->windowed_samples, AC3_WINDOW_SIZE *
52 sizeof(*s->windowed_samples), alloc_fail);
53 FF_ALLOC_OR_GOTO(s->avctx, s->planar_samples, s->channels * sizeof(*s->planar_samples),
55 for (ch = 0; ch < s->channels; ch++) {
56 FF_ALLOCZ_OR_GOTO(s->avctx, s->planar_samples[ch],
57 (AC3_FRAME_SIZE+AC3_BLOCK_SIZE) * sizeof(**s->planar_samples),
63 return AVERROR(ENOMEM);
68 * Deinterleave input samples.
69 * Channels are reordered from Libav's default order to AC-3 order.
71 static void deinterleave_input_samples(AC3EncodeContext *s,
72 const SampleType *samples)
76 /* deinterleave and remap input samples */
77 for (ch = 0; ch < s->channels; ch++) {
78 const SampleType *sptr;
81 /* copy last 256 samples of previous frame to the start of the current frame */
82 memcpy(&s->planar_samples[ch][0], &s->planar_samples[ch][AC3_FRAME_SIZE],
83 AC3_BLOCK_SIZE * sizeof(s->planar_samples[0][0]));
87 sptr = samples + s->channel_map[ch];
88 for (i = AC3_BLOCK_SIZE; i < AC3_FRAME_SIZE+AC3_BLOCK_SIZE; i++) {
89 s->planar_samples[ch][i] = *sptr;
97 * Apply the MDCT to input samples to generate frequency coefficients.
98 * This applies the KBD window and normalizes the input to reduce precision
99 * loss due to fixed-point calculations.
101 static void apply_mdct(AC3EncodeContext *s)
105 for (ch = 0; ch < s->channels; ch++) {
106 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
107 AC3Block *block = &s->blocks[blk];
108 const SampleType *input_samples = &s->planar_samples[ch][blk * AC3_BLOCK_SIZE];
110 apply_window(&s->dsp, s->windowed_samples, input_samples,
111 s->mdct_window, AC3_WINDOW_SIZE);
114 block->coeff_shift[ch+1] = normalize_samples(s);
116 s->mdct.mdct_calcw(&s->mdct, block->mdct_coef[ch+1],
117 s->windowed_samples);
124 * Calculate a single coupling coordinate.
126 static inline float calc_cpl_coord(float energy_ch, float energy_cpl)
130 coord *= sqrtf(energy_ch / energy_cpl);
136 * Calculate coupling channel and coupling coordinates.
137 * TODO: Currently this is only used for the floating-point encoder. I was
138 * able to make it work for the fixed-point encoder, but quality was
139 * generally lower in most cases than not using coupling. If a more
140 * adaptive coupling strategy were to be implemented it might be useful
141 * at that time to use coupling for the fixed-point encoder as well.
143 static void apply_channel_coupling(AC3EncodeContext *s)
145 #if CONFIG_AC3ENC_FLOAT
146 LOCAL_ALIGNED_16(float, cpl_coords, [AC3_MAX_BLOCKS], [AC3_MAX_CHANNELS][16]);
147 LOCAL_ALIGNED_16(int32_t, fixed_cpl_coords, [AC3_MAX_BLOCKS], [AC3_MAX_CHANNELS][16]);
148 int blk, ch, bnd, i, j;
149 CoefSumType energy[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS][16] = {{{0}}};
150 int cpl_start, num_cpl_coefs;
152 memset(cpl_coords, 0, AC3_MAX_BLOCKS * sizeof(*cpl_coords));
153 memset(fixed_cpl_coords, 0, AC3_MAX_BLOCKS * sizeof(*fixed_cpl_coords));
155 /* align start to 16-byte boundary. align length to multiple of 32.
156 note: coupling start bin % 4 will always be 1 */
157 cpl_start = s->start_freq[CPL_CH] - 1;
158 num_cpl_coefs = FFALIGN(s->num_cpl_subbands * 12 + 1, 32);
159 cpl_start = FFMIN(256, cpl_start + num_cpl_coefs) - num_cpl_coefs;
161 /* calculate coupling channel from fbw channels */
162 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
163 AC3Block *block = &s->blocks[blk];
164 CoefType *cpl_coef = &block->mdct_coef[CPL_CH][cpl_start];
165 if (!block->cpl_in_use)
167 memset(cpl_coef, 0, num_cpl_coefs * sizeof(*cpl_coef));
168 for (ch = 1; ch <= s->fbw_channels; ch++) {
169 CoefType *ch_coef = &block->mdct_coef[ch][cpl_start];
170 if (!block->channel_in_cpl[ch])
172 for (i = 0; i < num_cpl_coefs; i++)
173 cpl_coef[i] += ch_coef[i];
176 /* coefficients must be clipped in order to be encoded */
177 clip_coefficients(&s->dsp, cpl_coef, num_cpl_coefs);
179 /* scale coupling coefficients from float to 24-bit fixed-point */
180 s->ac3dsp.float_to_fixed24(&block->fixed_coef[CPL_CH][cpl_start],
181 cpl_coef, num_cpl_coefs);
184 /* calculate energy in each band in coupling channel and each fbw channel */
185 /* TODO: possibly use SIMD to speed up energy calculation */
187 i = s->start_freq[CPL_CH];
188 while (i < s->cpl_end_freq) {
189 int band_size = s->cpl_band_sizes[bnd];
190 for (ch = CPL_CH; ch <= s->fbw_channels; ch++) {
191 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
192 AC3Block *block = &s->blocks[blk];
193 if (!block->cpl_in_use || (ch > CPL_CH && !block->channel_in_cpl[ch]))
195 for (j = 0; j < band_size; j++) {
196 CoefType v = block->mdct_coef[ch][i+j];
197 MAC_COEF(energy[blk][ch][bnd], v, v);
205 /* determine which blocks to send new coupling coordinates for */
206 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
207 AC3Block *block = &s->blocks[blk];
208 AC3Block *block0 = blk ? &s->blocks[blk-1] : NULL;
210 CoefSumType coord_diff[AC3_MAX_CHANNELS] = {0,};
212 if (block->cpl_in_use) {
213 /* calculate coupling coordinates for all blocks and calculate the
214 average difference between coordinates in successive blocks */
215 for (ch = 1; ch <= s->fbw_channels; ch++) {
216 if (!block->channel_in_cpl[ch])
219 for (bnd = 0; bnd < s->num_cpl_bands; bnd++) {
220 cpl_coords[blk][ch][bnd] = calc_cpl_coord(energy[blk][ch][bnd],
221 energy[blk][CPL_CH][bnd]);
222 if (blk > 0 && block0->cpl_in_use &&
223 block0->channel_in_cpl[ch]) {
224 coord_diff[ch] += fabs(cpl_coords[blk-1][ch][bnd] -
225 cpl_coords[blk ][ch][bnd]);
228 coord_diff[ch] /= s->num_cpl_bands;
231 /* send new coordinates if this is the first block, if previous
232 * block did not use coupling but this block does, the channels
233 * using coupling has changed from the previous block, or the
234 * coordinate difference from the last block for any channel is
235 * greater than a threshold value. */
238 } else if (!block0->cpl_in_use) {
241 for (ch = 1; ch <= s->fbw_channels; ch++) {
242 if (block->channel_in_cpl[ch] && !block0->channel_in_cpl[ch]) {
248 for (ch = 1; ch <= s->fbw_channels; ch++) {
249 if (block->channel_in_cpl[ch] && coord_diff[ch] > 0.04) {
257 block->new_cpl_coords = new_coords;
260 /* calculate final coupling coordinates, taking into account reusing of
261 coordinates in successive blocks */
262 for (bnd = 0; bnd < s->num_cpl_bands; bnd++) {
264 while (blk < AC3_MAX_BLOCKS) {
266 CoefSumType energy_cpl;
267 AC3Block *block = &s->blocks[blk];
269 if (!block->cpl_in_use) {
274 energy_cpl = energy[blk][CPL_CH][bnd];
276 while (!s->blocks[blk1].new_cpl_coords && blk1 < AC3_MAX_BLOCKS) {
277 if (s->blocks[blk1].cpl_in_use)
278 energy_cpl += energy[blk1][CPL_CH][bnd];
282 for (ch = 1; ch <= s->fbw_channels; ch++) {
284 if (!block->channel_in_cpl[ch])
286 energy_ch = energy[blk][ch][bnd];
288 while (!s->blocks[blk1].new_cpl_coords && blk1 < AC3_MAX_BLOCKS) {
289 if (s->blocks[blk1].cpl_in_use)
290 energy_ch += energy[blk1][ch][bnd];
293 cpl_coords[blk][ch][bnd] = calc_cpl_coord(energy_ch, energy_cpl);
299 /* calculate exponents/mantissas for coupling coordinates */
300 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
301 AC3Block *block = &s->blocks[blk];
302 if (!block->cpl_in_use || !block->new_cpl_coords)
305 clip_coefficients(&s->dsp, cpl_coords[blk][1], s->fbw_channels * 16);
306 s->ac3dsp.float_to_fixed24(fixed_cpl_coords[blk][1],
308 s->fbw_channels * 16);
309 s->ac3dsp.extract_exponents(block->cpl_coord_exp[1],
310 fixed_cpl_coords[blk][1],
311 s->fbw_channels * 16);
313 for (ch = 1; ch <= s->fbw_channels; ch++) {
314 int bnd, min_exp, max_exp, master_exp;
316 /* determine master exponent */
317 min_exp = max_exp = block->cpl_coord_exp[ch][0];
318 for (bnd = 1; bnd < s->num_cpl_bands; bnd++) {
319 int exp = block->cpl_coord_exp[ch][bnd];
320 min_exp = FFMIN(exp, min_exp);
321 max_exp = FFMAX(exp, max_exp);
323 master_exp = ((max_exp - 15) + 2) / 3;
324 master_exp = FFMAX(master_exp, 0);
325 while (min_exp < master_exp * 3)
327 for (bnd = 0; bnd < s->num_cpl_bands; bnd++) {
328 block->cpl_coord_exp[ch][bnd] = av_clip(block->cpl_coord_exp[ch][bnd] -
329 master_exp * 3, 0, 15);
331 block->cpl_master_exp[ch] = master_exp;
333 /* quantize mantissas */
334 for (bnd = 0; bnd < s->num_cpl_bands; bnd++) {
335 int cpl_exp = block->cpl_coord_exp[ch][bnd];
336 int cpl_mant = (fixed_cpl_coords[blk][ch][bnd] << (5 + cpl_exp + master_exp * 3)) >> 24;
342 block->cpl_coord_mant[ch][bnd] = cpl_mant;
347 if (CONFIG_EAC3_ENCODER && s->eac3)
348 ff_eac3_set_cpl_states(s);
349 #endif /* CONFIG_AC3ENC_FLOAT */
354 * Determine rematrixing flags for each block and band.
356 static void compute_rematrixing_strategy(AC3EncodeContext *s)
360 AC3Block *block, *av_uninit(block0);
362 if (s->channel_mode != AC3_CHMODE_STEREO)
365 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
366 block = &s->blocks[blk];
367 block->new_rematrixing_strategy = !blk;
369 if (!s->rematrixing_enabled) {
374 block->num_rematrixing_bands = 4;
375 if (block->cpl_in_use) {
376 block->num_rematrixing_bands -= (s->start_freq[CPL_CH] <= 61);
377 block->num_rematrixing_bands -= (s->start_freq[CPL_CH] == 37);
378 if (blk && block->num_rematrixing_bands != block0->num_rematrixing_bands)
379 block->new_rematrixing_strategy = 1;
381 nb_coefs = FFMIN(block->end_freq[1], block->end_freq[2]);
383 for (bnd = 0; bnd < block->num_rematrixing_bands; bnd++) {
384 /* calculate calculate sum of squared coeffs for one band in one block */
385 int start = ff_ac3_rematrix_band_tab[bnd];
386 int end = FFMIN(nb_coefs, ff_ac3_rematrix_band_tab[bnd+1]);
387 CoefSumType sum[4] = {0,};
388 for (i = start; i < end; i++) {
389 CoefType lt = block->mdct_coef[1][i];
390 CoefType rt = block->mdct_coef[2][i];
391 CoefType md = lt + rt;
392 CoefType sd = lt - rt;
393 MAC_COEF(sum[0], lt, lt);
394 MAC_COEF(sum[1], rt, rt);
395 MAC_COEF(sum[2], md, md);
396 MAC_COEF(sum[3], sd, sd);
399 /* compare sums to determine if rematrixing will be used for this band */
400 if (FFMIN(sum[2], sum[3]) < FFMIN(sum[0], sum[1]))
401 block->rematrixing_flags[bnd] = 1;
403 block->rematrixing_flags[bnd] = 0;
405 /* determine if new rematrixing flags will be sent */
407 block->rematrixing_flags[bnd] != block0->rematrixing_flags[bnd]) {
408 block->new_rematrixing_strategy = 1;
417 * Encode a single AC-3 frame.
419 int AC3_NAME(encode_frame)(AVCodecContext *avctx, unsigned char *frame,
420 int buf_size, void *data)
422 AC3EncodeContext *s = avctx->priv_data;
423 const SampleType *samples = data;
426 if (!s->eac3 && s->options.allow_per_frame_metadata) {
427 ret = ff_ac3_validate_metadata(s);
432 if (s->bit_alloc.sr_code == 1 || s->eac3)
433 ff_ac3_adjust_frame_size(s);
435 deinterleave_input_samples(s, samples);
440 scale_coefficients(s);
442 clip_coefficients(&s->dsp, s->blocks[0].mdct_coef[1],
443 AC3_MAX_COEFS * AC3_MAX_BLOCKS * s->channels);
445 s->cpl_on = s->cpl_enabled;
446 ff_ac3_compute_coupling_strategy(s);
449 apply_channel_coupling(s);
451 compute_rematrixing_strategy(s);
454 scale_coefficients(s);
456 ff_ac3_apply_rematrixing(s);
458 ff_ac3_process_exponents(s);
460 ret = ff_ac3_compute_bit_allocation(s);
462 av_log(avctx, AV_LOG_ERROR, "Bit allocation failed. Try increasing the bitrate.\n");
466 ff_ac3_quantize_mantissas(s);
468 ff_ac3_output_frame(s, frame);
470 return s->frame_size;