Add okayed chunks of AAC encoder psychoacoustic model

Originally committed as revision 14822 to svn://svn.ffmpeg.org/ffmpeg/trunk

1 files changed, 104 insertions, 0 deletions

diff --git a/libavcodec/aacpsy.c b/libavcodec/aacpsy.c
new file mode 100644
index 0000000000..5a8a8522e9
--- /dev/null
+++ b/libavcodec/aacpsy.c
@@ -0,0 +1,104 @@
+/*
+ * AAC encoder psychoacoustic model
+ * Copyright (C) 2008 Konstantin Shishkov
+ *
+ * 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 aacpsy.c
+ * AAC encoder psychoacoustic model
+ */
+
+#include "avcodec.h"
+#include "aacpsy.h"
+#include "aactab.h"
+
+/***********************************
+ *              TODOs:
+ * General:
+ * better audio preprocessing (add DC highpass filter?)
+ * more psy models
+ * maybe improve coefficient quantization function in some way
+ *
+ * 3GPP-based psy model:
+ * thresholds linearization after their modifications for attaining given bitrate
+ * try other bitrate controlling mechanism (maybe use ratecontrol.c?)
+ * control quality for quality-based output
+ **********************************/
+
+/**
+ * Quantize one coefficient.
+ * @return absolute value of the quantized coefficient
+ * @see 3GPP TS26.403 5.6.2 "Scalefactor determination"
+ */
+static av_always_inline int quant(float coef, const float Q)
+{
+    return av_clip((int)(pow(fabsf(coef) * Q, 0.75) + 0.4054), 0, 8191);
+}
+
+static inline float get_approximate_quant_error(float *c, int size, int scale_idx)
+{
+    int i;
+    int q;
+    float coef, unquant, sum = 0.0f;
+    const float Q  = ff_aac_pow2sf_tab[200 - scale_idx + SCALE_ONE_POS - SCALE_DIV_512];
+    const float IQ = ff_aac_pow2sf_tab[200 + scale_idx - SCALE_ONE_POS + SCALE_DIV_512];
+    for(i = 0; i < size; i++){
+        coef = fabs(c[i]);
+        q = quant(c[i], Q);
+        unquant = (q * cbrt(q)) * IQ;
+        sum += (coef - unquant) * (coef - unquant);
+    }
+    return sum;
+}
+
+/**
+ * constants for 3GPP AAC psychoacoustic model
+ * @{
+ */
+#define PSY_3GPP_SPREAD_LOW  1.5f // spreading factor for ascending threshold spreading  (15 dB/Bark)
+#define PSY_3GPP_SPREAD_HI   3.0f // spreading factor for descending threshold spreading (30 dB/Bark)
+/**
+ * @}
+ */
+
+/**
+ * information for single band used by 3GPP TS26.403-inspired psychoacoustic model
+ */
+typedef struct Psy3gppBand{
+    float energy;    ///< band energy
+    float ffac;      ///< form factor
+}Psy3gppBand;
+
+/**
+ * psychoacoustic model frame type-dependent coefficients
+ */
+typedef struct Psy3gppCoeffs{
+    float ath       [64]; ///< absolute threshold of hearing per bands
+    float barks     [64]; ///< Bark value for each spectral band in long frame
+    float spread_low[64]; ///< spreading factor for low-to-high threshold spreading in long frame
+    float spread_hi [64]; ///< spreading factor for high-to-low threshold spreading in long frame
+}Psy3gppCoeffs;
+
+/**
+ * Calculate Bark value for given line.
+ */
+static inline float calc_bark(float f)
+{
+    return 13.3f * atanf(0.00076f * f) + 3.5f * atanf((f / 7500.0f) * (f / 7500.0f));
+}