From a83a8d70681a7093ff4bd8232b8f75fed3d6af48 Mon Sep 17 00:00:00 2001 From: Rostislav Pehlivanov Date: Sat, 12 Sep 2015 13:04:27 +0100 Subject: aacenc_tns: redo coefficient quantization and decision making This finally (and again) gets rid of basically everything the specifications say about how TNS should be done. The main problem used to be that a single filter was used for all coefficients which despite being explicitly recommended by the specifications usually sounds wrong, therefore it's a corner case in the current TNS implementation. This commit also changes the coefficient bit size, as apparently it's better to use lower precision in case the windows are eight short. This is apparently what fdk_aac uses, looking at the bit stream and makes sense. Also the order when 8 SHORT windows happen is important as 7 was too much and according to PSNR was worse while 5 is just about correct. Signed-off-by: Rostislav Pehlivanov --- libavcodec/aacenc_tns.c | 60 ++++++++++++++++++++++++++++--------------------- 1 file changed, 34 insertions(+), 26 deletions(-) (limited to 'libavcodec/aacenc_tns.c') diff --git a/libavcodec/aacenc_tns.c b/libavcodec/aacenc_tns.c index 637b813..da353d6 100644 --- a/libavcodec/aacenc_tns.c +++ b/libavcodec/aacenc_tns.c @@ -67,20 +67,6 @@ void ff_aac_encode_tns_info(AACEncContext *s, SingleChannelElement *sce) } } -static inline void quantize_coefs(double *coef, int *idx, float *lpc, int order) -{ - int i; - uint8_t u_coef; - const float *quant_arr = tns_tmp2_map[TNS_Q_BITS == 4]; - const double iqfac_p = ((1 << (TNS_Q_BITS-1)) - 0.5)/(M_PI/2.0); - const double iqfac_m = ((1 << (TNS_Q_BITS-1)) + 0.5)/(M_PI/2.0); - for (i = 0; i < order; i++) { - idx[i] = ceilf(asin(coef[i])*((coef[i] >= 0) ? iqfac_p : iqfac_m)); - u_coef = (idx[i])&(~(~0<tns; int w, w2, g, count = 0; const int mmm = FFMIN(sce->ics.tns_max_bands, sce->ics.max_sfb); const int is8 = sce->ics.window_sequence[0] == EIGHT_SHORT_SEQUENCE; - const int order = is8 ? 7 : s->profile == FF_PROFILE_AAC_LOW ? 12 : TNS_MAX_ORDER; + const int c_bits = is8 ? TNS_Q_BITS_SHORT == 4 : TNS_Q_BITS == 4; int sfb_start = av_clip(tns_min_sfb[is8][s->samplerate_index], 0, mmm); int sfb_end = av_clip(sce->ics.num_swb, 0, mmm); for (w = 0; w < sce->ics.num_windows; w++) { - float e_ratio = 0.0f, threshold = 0.0f, spread = 0.0f, en[2] = {0.0, 0.0f}; - double gain = 0.0f, coefs[MAX_LPC_ORDER] = {0}; + int use_tns; + int order = is8 ? 5 : s->profile == FF_PROFILE_AAC_LOW ? 12 : TNS_MAX_ORDER; int coef_start = w*sce->ics.num_swb + sce->ics.swb_offset[sfb_start]; int coef_len = sce->ics.swb_offset[sfb_end] - sce->ics.swb_offset[sfb_start]; + float e_ratio = 0.0f, threshold = 0.0f, spread = 0.0f, en[2] = {0.0, 0.0f}; + double gain = 0.0f, coefs[MAX_LPC_ORDER] = {0}; for (g = 0; g < sce->ics.num_swb; g++) { if (w*16+g < sfb_start || w*16+g > sfb_end) @@ -149,22 +154,26 @@ void ff_aac_search_for_tns(AACEncContext *s, SingleChannelElement *sce) else en[0] += band->energy; threshold += band->threshold; - spread += band->spread; + spread += band->spread; } } if (coef_len <= 0 || (sfb_end - sfb_start) <= 0) continue; - else - e_ratio = en[0]/en[1]; /* LPC */ gain = ff_lpc_calc_ref_coefs_f(&s->lpc, &sce->coeffs[coef_start], coef_len, order, coefs); - if (gain > TNS_GAIN_THRESHOLD_LOW && gain < TNS_GAIN_THRESHOLD_HIGH && - (en[0]+en[1]) > TNS_GAIN_THRESHOLD_LOW*threshold && - spread < TNS_SPREAD_THRESHOLD && order) { + if (!order || gain < TNS_GAIN_THRESHOLD_LOW || gain > TNS_GAIN_THRESHOLD_HIGH) + use_tns = 0; + else if ((en[0]+en[1]) < TNS_GAIN_THRESHOLD_LOW*threshold || spread < TNS_SPREAD_THRESHOLD) + use_tns = 0; + else + use_tns = 1; + + if (use_tns) { + e_ratio = en[0]/en[1]; if (is8 || order < 2 || (e_ratio > TNS_E_RATIO_LOW && e_ratio < TNS_E_RATIO_HIGH)) { tns->n_filt[w] = 1; for (g = 0; g < tns->n_filt[w]; g++) { @@ -172,7 +181,7 @@ void ff_aac_search_for_tns(AACEncContext *s, SingleChannelElement *sce) tns->direction[w][g] = en[0] < en[1]; tns->order[w][g] = order; quantize_coefs(coefs, tns->coef_idx[w][g], tns->coef[w][g], - order); + order, c_bits); } } else { /* 2 filters due to energy disbalance */ tns->n_filt[w] = 2; @@ -183,12 +192,11 @@ void ff_aac_search_for_tns(AACEncContext *s, SingleChannelElement *sce) (sfb_end - sfb_start) - tns->length[w][g-1]; quantize_coefs(&coefs[!g ? 0 : order - tns->order[w][g-1]], tns->coef_idx[w][g], tns->coef[w][g], - tns->order[w][g]); + tns->order[w][g], c_bits); } } count++; } } - sce->tns.present = !!count; } -- cgit v1.1