From b6cc8ec7ecc3bea2a84fe65fa278e22fbb26a48c Mon Sep 17 00:00:00 2001
From: Rostislav Pehlivanov <atomnuker@gmail.com>
Date: Mon, 7 Sep 2015 12:39:04 +0100
Subject: [PATCH] aaccoder: add frequency scaling and quantization correction
for PNS
This commit once again improves the PNS implementation by scaling the
thresholds with frequency. The thresholds get looser as the frequency
increases since higher frequencies are basically noise to human ears.
Also, this introduces quantization error correction for PNS. Should
the error be too much, no PNS will be used. The energy_ratio is used
to regulate the actual encoded PNS energy: if the generated PNS
energy is higher than the energy from the psy system, energy_ratio
is used to correct it so that hopefully once requantized and
transmitted the value in the decoder will be closer to what the
encoder has.
Signed-off-by: Rostislav Pehlivanov <atomnuker@gmail.com>
---
libavcodec/aaccoder.c | 28 +++++++++++++++++-----------
tests/fate/aac.mak | 2 +-
2 files changed, 18 insertions(+), 12 deletions(-)
diff --git a/libavcodec/aaccoder.c b/libavcodec/aaccoder.c
index 8a241d2c067..cf4b11b3bc9 100644
--- a/libavcodec/aaccoder.c
+++ b/libavcodec/aaccoder.c
@@ -876,36 +876,39 @@ static void search_for_pns(AACEncContext *s, AVCodecContext *avctx, SingleChanne
for (g = 0; g < sce->ics.num_swb; g++) {
int noise_sfi, try_pns = 0;
float dist1 = 0.0f, dist2 = 0.0f, noise_amp;
- float energy = 0.0f, threshold = 0.0f, spread = 0.0f;
+ float pns_energy = 0.0f, energy_ratio, dist_thresh;
+ float sfb_energy = 0.0f, threshold = 0.0f, spread = 0.0f;
+ float freq_boost = FFMAX(0.88f*start*freq_mult/NOISE_LOW_LIMIT, 1.0f);
if (start*freq_mult < NOISE_LOW_LIMIT) {
start += sce->ics.swb_sizes[g];
continue;
+ } else {
+ dist_thresh = FFMIN(0.008f*(NOISE_LOW_LIMIT/start*freq_mult), 1.11f);
}
for (w2 = 0; w2 < sce->ics.group_len[w]; w2++) {
band = &s->psy.ch[s->cur_channel].psy_bands[(w+w2)*16+g];
- energy += band->energy;
- spread += band->spread;
- threshold += band->threshold;
+ sfb_energy += band->energy;
+ spread += band->spread;
+ threshold += band->threshold;
}
- sce->pns_ener[w*16+g] = energy;
if (sce->zeroes[w*16+g]) {
try_pns = 1;
- } else if (energy < threshold) {
+ } else if (sfb_energy < threshold*freq_boost) {
try_pns = 1;
} else if (spread > spread_threshold) {
try_pns = 0;
- } else if (energy < threshold*thr_mult) {
+ } else if (sfb_energy < threshold*thr_mult*freq_boost) {
try_pns = 1;
}
- if (!try_pns || !energy) {
+ if (!try_pns || !sfb_energy) {
start += sce->ics.swb_sizes[g];
continue;
}
- noise_sfi = av_clip(roundf(log2f(energy)*2), -100, 155); /* Quantize */
- noise_amp = -ff_aac_pow2sf_tab[noise_sfi + POW_SF2_ZERO]; /* Dequantize */
+ noise_sfi = av_clip(roundf(log2f(sfb_energy)*2), -100, 155); /* Quantize */
+ noise_amp = -ff_aac_pow2sf_tab[noise_sfi + POW_SF2_ZERO]; /* Dequantize */
for (w2 = 0; w2 < sce->ics.group_len[w]; w2++) {
float band_energy, scale;
band = &s->psy.ch[s->cur_channel+0].psy_bands[(w+w2)*16+g];
@@ -914,6 +917,7 @@ static void search_for_pns(AACEncContext *s, AVCodecContext *avctx, SingleChanne
band_energy = s->fdsp->scalarproduct_float(PNS, PNS, sce->ics.swb_sizes[g]);
scale = noise_amp/sqrtf(band_energy);
s->fdsp->vector_fmul_scalar(PNS, PNS, scale, sce->ics.swb_sizes[g]);
+ pns_energy += s->fdsp->scalarproduct_float(PNS, PNS, sce->ics.swb_sizes[g]);
abs_pow34_v(NOR34, &sce->coeffs[start+(w+w2)*128], sce->ics.swb_sizes[g]);
abs_pow34_v(PNS34, PNS, sce->ics.swb_sizes[g]);
dist1 += quantize_band_cost(s, &sce->coeffs[start + (w+w2)*128],
@@ -929,7 +933,9 @@ static void search_for_pns(AACEncContext *s, AVCodecContext *avctx, SingleChanne
NOISE_BT,
lambda/band->threshold, INFINITY, NULL, 0);
}
- if (dist2 < dist1) {
+ energy_ratio = sfb_energy/pns_energy; /* Compensates for quantization error */
+ sce->pns_ener[w*16+g] = energy_ratio*sfb_energy;
+ if (energy_ratio > 0.80f && energy_ratio < 1.20f && dist1/dist2 > dist_thresh) {
sce->band_type[w*16+g] = NOISE_BT;
sce->zeroes[w*16+g] = 0;
if (sce->band_type[w*16+g-1] != NOISE_BT && /* Prevent holes */
diff --git a/tests/fate/aac.mak b/tests/fate/aac.mak
index 910bac00c82..4391106c9a5 100644
--- a/tests/fate/aac.mak
+++ b/tests/fate/aac.mak
@@ -163,7 +163,7 @@ fate-aac-pns-encode: CMD = enc_dec_pcm adts wav s16le $(TARGET_SAMPLES)/audio-re
fate-aac-pns-encode: CMP = stddev
fate-aac-pns-encode: REF = $(SAMPLES)/audio-reference/luckynight_2ch_44kHz_s16.wav
fate-aac-pns-encode: CMP_SHIFT = -4096
-fate-aac-pns-encode: CMP_TARGET = 647.11
+fate-aac-pns-encode: CMP_TARGET = 637.66
fate-aac-pns-encode: SIZE_TOLERANCE = 3560
fate-aac-pns-encode: FUZZ = 5
--
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