mirror of https://git.ffmpeg.org/ffmpeg.git
101 lines
3.0 KiB
C
101 lines
3.0 KiB
C
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/*
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* AAC decoder
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* Copyright (c) 2005-2006 Oded Shimon ( ods15 ods15 dyndns org )
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* Copyright (c) 2006-2007 Maxim Gavrilov ( maxim.gavrilov gmail com )
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* Copyright (c) 2008-2013 Alex Converse <alex.converse@gmail.com>
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*
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* AAC LATM decoder
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* Copyright (c) 2008-2010 Paul Kendall <paul@kcbbs.gen.nz>
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* Copyright (c) 2010 Janne Grunau <janne-libav@jannau.net>
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*
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* AAC decoder fixed-point implementation
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* Copyright (c) 2013
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* MIPS Technologies, Inc., California.
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*
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* This file is part of FFmpeg.
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*
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* FFmpeg is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* FFmpeg is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with FFmpeg; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#ifndef AVCODEC_AAC_AACDEC_FLOAT_PREDICTION_H
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#define AVCODEC_AAC_AACDEC_FLOAT_PREDICTION_H
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static av_always_inline float flt16_round(float pf)
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{
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union av_intfloat32 tmp;
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tmp.f = pf;
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tmp.i = (tmp.i + 0x00008000U) & 0xFFFF0000U;
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return tmp.f;
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}
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static av_always_inline float flt16_even(float pf)
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{
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union av_intfloat32 tmp;
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tmp.f = pf;
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tmp.i = (tmp.i + 0x00007FFFU + (tmp.i & 0x00010000U >> 16)) & 0xFFFF0000U;
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return tmp.f;
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}
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static av_always_inline float flt16_trunc(float pf)
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{
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union av_intfloat32 pun;
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pun.f = pf;
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pun.i &= 0xFFFF0000U;
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return pun.f;
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}
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static av_always_inline void predict(PredictorState *ps, float *coef,
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int output_enable)
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{
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const float a = 0.953125; // 61.0 / 64
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const float alpha = 0.90625; // 29.0 / 32
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float e0, e1;
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float pv;
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float k1, k2;
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float r0 = ps->r0, r1 = ps->r1;
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float cor0 = ps->cor0, cor1 = ps->cor1;
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float var0 = ps->var0, var1 = ps->var1;
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k1 = var0 > 1 ? cor0 * flt16_even(a / var0) : 0;
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k2 = var1 > 1 ? cor1 * flt16_even(a / var1) : 0;
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pv = flt16_round(k1 * r0 + k2 * r1);
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if (output_enable)
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*coef += pv;
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e0 = *coef;
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e1 = e0 - k1 * r0;
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ps->cor1 = flt16_trunc(alpha * cor1 + r1 * e1);
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ps->var1 = flt16_trunc(alpha * var1 + 0.5f * (r1 * r1 + e1 * e1));
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ps->cor0 = flt16_trunc(alpha * cor0 + r0 * e0);
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ps->var0 = flt16_trunc(alpha * var0 + 0.5f * (r0 * r0 + e0 * e0));
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ps->r1 = flt16_trunc(a * (r0 - k1 * e0));
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ps->r0 = flt16_trunc(a * e0);
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}
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static av_always_inline void reset_predict_state(PredictorState *ps)
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{
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ps->r0 = 0.0f;
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ps->r1 = 0.0f;
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ps->cor0 = 0.0f;
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ps->cor1 = 0.0f;
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ps->var0 = 1.0f;
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ps->var1 = 1.0f;
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}
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#endif /* AVCODEC_AAC_AACDEC_FLOAT_PREDICTION_H */
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