diff options
Diffstat (limited to 'libavcodec/aacenc_tns.c')
| -rw-r--r-- | libavcodec/aacenc_tns.c | 235 |
1 files changed, 235 insertions, 0 deletions
diff --git a/libavcodec/aacenc_tns.c b/libavcodec/aacenc_tns.c new file mode 100644 index 0000000000..50ac29c05c --- /dev/null +++ b/libavcodec/aacenc_tns.c @@ -0,0 +1,235 @@ +/* + * AAC encoder TNS + * Copyright (C) 2015 Rostislav Pehlivanov + * + * This file is part of FFmpeg. + * + * FFmpeg is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public + * License as published by the Free Software Foundation; either + * version 2.1 of the License, or (at your option) any later version. + * + * FFmpeg is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with FFmpeg; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA + */ + +/** + * @file + * AAC encoder temporal noise shaping + * @author Rostislav Pehlivanov ( atomnuker gmail com ) + */ + +#include <strings.h> +#include "aacenc.h" +#include "aacenc_tns.h" +#include "aactab.h" +#include "aacenc_utils.h" +#include "aacenc_quantization.h" + +static inline void conv_to_int32(int32_t *loc, float *samples, int num, float norm) +{ + int i; + for (i = 0; i < num; i++) + loc[i] = ceilf((samples[i]/norm)*INT32_MAX); +} + +static inline void conv_to_float(float *arr, int32_t *cof, int num) +{ + int i; + for (i = 0; i < num; i++) + arr[i] = (float)cof[i]/INT32_MAX; +} + +/* Input: quantized 4 bit coef, output: 1 if first (MSB) 2 bits are the same */ +static inline int coef_test_compression(int coef) +{ + int res = 0; + coef = coef >> 3; + res += ffs(coef); + coef = coef >> 1; + res += ffs(coef); + return res == 1 ? 0 : 1; +} + +static inline int compress_coef(int *coefs, int num) +{ + int i, res = 0; + for (i = 0; i < num; i++) + res += coef_test_compression(coefs[i]); + return res != num ? 0 : 1; +} + +/** + * Encode TNS data. + * Coefficient compression saves a single bit. + */ +void encode_tns_info(AACEncContext *s, SingleChannelElement *sce) +{ + int i, w, filt, coef_len, coef_compress; + const int coef_res = MAX_LPC_PRECISION == 4 ? 1 : 0; + const int is8 = sce->ics.window_sequence[0] == EIGHT_SHORT_SEQUENCE; + + put_bits(&s->pb, 1, !!sce->tns.present); + + if (!sce->tns.present) + return; + + for (i = 0; i < sce->ics.num_windows; i++) { + put_bits(&s->pb, 2 - is8, sce->tns.n_filt[i]); + if (sce->tns.n_filt[i]) { + put_bits(&s->pb, 1, !!coef_res); + for (filt = 0; filt < sce->tns.n_filt[i]; filt++) { + put_bits(&s->pb, 6 - 2 * is8, sce->tns.length[i][filt]); + put_bits(&s->pb, 5 - 2 * is8, sce->tns.order[i][filt]); + if (sce->tns.order[i][filt]) { + coef_compress = compress_coef(sce->tns.coef_idx[i][filt], + sce->tns.order[i][filt]); + put_bits(&s->pb, 1, !!sce->tns.direction[i][filt]); + put_bits(&s->pb, 1, !!coef_compress); + coef_len = coef_res + 3 - coef_compress; + for (w = 0; w < sce->tns.order[i][filt]; w++) + put_bits(&s->pb, coef_len, sce->tns.coef_idx[i][filt][w]); + } + } + } + } +} + +static int process_tns_coeffs(TemporalNoiseShaping *tns, float *tns_coefs_raw, + int order, int w, int filt) +{ + int i, j; + int *idx = tns->coef_idx[w][filt]; + float *lpc = tns->coef[w][filt]; + const int iqfac_p = ((1 << (MAX_LPC_PRECISION-1)) - 0.5)/(M_PI/2.0); + const int iqfac_m = ((1 << (MAX_LPC_PRECISION-1)) + 0.5)/(M_PI/2.0); + float temp[TNS_MAX_ORDER] = {0.0f}, out[TNS_MAX_ORDER] = {0.0f}; + + /* Quantization */ + for (i = 0; i < order; i++) { + idx[i] = ceilf(asin(tns_coefs_raw[i])*((tns_coefs_raw[i] >= 0) ? iqfac_p : iqfac_m)); + lpc[i] = 2*sin(idx[i]/((idx[i] >= 0) ? iqfac_p : iqfac_m)); + } + + /* Trim any coeff less than 0.1f from the end */ + for (i = order; i > -1; i--) { + lpc[i] = (fabs(lpc[i]) > 0.1f) ? lpc[i] : 0.0f; + if (lpc[i] != 0.0 ) { + order = i; + break; + } + } + + if (!order) + return 0; + + /* Step up procedure, convert to LPC coeffs */ + out[0] = 1.0f; + for (i = 1; i <= order; i++) { + for (j = 1; j < i; j++) { + temp[j] = out[j] + lpc[i]*out[i-j]; + } + for (j = 1; j <= i; j++) { + out[j] = temp[j]; + } + out[i] = lpc[i-1]; + } + memcpy(lpc, out, TNS_MAX_ORDER*sizeof(float)); + + return order; +} + +static void apply_tns_filter(float *out, float *in, int order, int direction, + float *tns_coefs, int ltp_used, int w, int filt, int start_i, int len) +{ + int i, j, inc, start = start_i; + float tmp[TNS_MAX_ORDER+1]; + if (direction) { + inc = -1; + start = (start + len) - 1; + } else { + inc = 1; + } + if (!ltp_used) { /* AR filter */ + for (i = 0; i < len; i++, start += inc) + out[i] = in[start]; + for (j = 1; j <= FFMIN(i, order); j++) + out[i] += tns_coefs[j]*in[start - j*inc]; + } else { /* MA filter */ + for (i = 0; i < len; i++, start += inc) { + tmp[0] = out[i] = in[start]; + for (j = 1; j <= FFMIN(i, order); j++) + out[i] += tmp[j]*tns_coefs[j]; + for (j = order; j > 0; j--) + tmp[j] = tmp[j - 1]; + } + } +} + +void search_for_tns(AACEncContext *s, SingleChannelElement *sce) +{ + TemporalNoiseShaping *tns = &sce->tns; + int w, g, order, sfb_start, sfb_len, coef_start, shift[MAX_LPC_ORDER], count = 0; + const int is8 = sce->ics.window_sequence[0] == EIGHT_SHORT_SEQUENCE; + const int tns_max_order = is8 ? 7 : s->profile == FF_PROFILE_AAC_LOW ? 12 : TNS_MAX_ORDER; + const float freq_mult = mpeg4audio_sample_rates[s->samplerate_index]/(1024.0f/sce->ics.num_windows)/2.0f; + float max_coef = 0.0f; + + for (coef_start = 0; coef_start < 1024; coef_start++) + max_coef = FFMAX(max_coef, sce->pcoeffs[coef_start]); + + for (w = 0; w < sce->ics.num_windows; w++) { + int filters = 1, start = 0, coef_len = 0; + int32_t conv_coeff[1024] = {0}; + int32_t coefs_t[MAX_LPC_ORDER][MAX_LPC_ORDER] = {{0}}; + + /* Determine start sfb + coef - excludes anything below threshold */ + for (g = 0; g < sce->ics.num_swb; g++) { + if (start*freq_mult > TNS_LOW_LIMIT) { + sfb_start = w*16+g; + sfb_len = (w+1)*16 + g - sfb_start; + coef_start = sce->ics.swb_offset[sfb_start]; + coef_len = sce->ics.swb_offset[sfb_start + sfb_len] - coef_start; + break; + } + start += sce->ics.swb_sizes[g]; + } + + if (coef_len <= 0) + continue; + + conv_to_int32(conv_coeff, &sce->pcoeffs[coef_start], coef_len, max_coef); + + /* LPC */ + order = ff_lpc_calc_coefs(&s->lpc, conv_coeff, coef_len, + TNS_MIN_PRED_ORDER, tns_max_order, + 32, coefs_t, shift, + FF_LPC_TYPE_LEVINSON, 10, + ORDER_METHOD_EST, MAX_LPC_SHIFT, 0) - 1; + + /* Works surprisingly well, remember to tweak MAX_LPC_SHIFT if you want to play around with this */ + if (shift[order] > 3) { + int direction = 0; + float tns_coefs_raw[TNS_MAX_ORDER]; + tns->n_filt[w] = filters++; + conv_to_float(tns_coefs_raw, coefs_t[order], order); + for (g = 0; g < tns->n_filt[w]; g++) { + process_tns_coeffs(tns, tns_coefs_raw, order, w, g); + apply_tns_filter(&sce->coeffs[coef_start], sce->pcoeffs, order, direction, tns->coef[w][g], + sce->ics.ltp.present, w, g, coef_start, coef_len); + tns->order[w][g] = order; + tns->length[w][g] = sfb_len; + tns->direction[w][g] = direction; + } + count++; + } + } + + sce->tns.present = !!count; +} |