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This increases the accuracy of coefficients, leading to improved quality. Rescaling of the coefficients to full 25-bit accuracy is done rather than offsetting the exponent values. This requires coefficient scaling to be done before determining the rematrixing strategy. Also, the rematrixing strategy calculation must use 64-bit math to prevent overflow due to the higher precision coefficients.
48 lines
1.4 KiB
C
48 lines
1.4 KiB
C
/*
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* The simplest AC-3 encoder
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* Copyright (c) 2000 Fabrice Bellard
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* Copyright (c) 2006-2010 Justin Ruggles <justin.ruggles@gmail.com>
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* Copyright (c) 2006-2010 Prakash Punnoor <prakash@punnoor.de>
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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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/**
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* @file
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* floating-point AC-3 encoder header.
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*/
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#ifndef AVCODEC_AC3ENC_FLOAT_H
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#define AVCODEC_AC3ENC_FLOAT_H
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#include "fft.h"
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typedef float SampleType;
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typedef float CoefType;
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typedef float CoefSumType;
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#define MAC_COEF(d,a,b) ((d)+=(a)*(b))
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typedef struct AC3MDCTContext {
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const float *window; ///< MDCT window function
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FFTContext fft; ///< FFT context for MDCT calculation
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} AC3MDCTContext;
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#endif /* AVCODEC_AC3ENC_FLOAT_H */
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