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FFmpeg/libavcodec/ac3enc_float.h
Justin 323e6fead0 ac3enc: do not right-shift fixed-point coefficients in the final MDCT stage.
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.
2011-03-14 08:45:26 -04:00

48 lines
1.4 KiB
C

/*
* The simplest AC-3 encoder
* Copyright (c) 2000 Fabrice Bellard
* Copyright (c) 2006-2010 Justin Ruggles <justin.ruggles@gmail.com>
* Copyright (c) 2006-2010 Prakash Punnoor <prakash@punnoor.de>
*
* 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
* floating-point AC-3 encoder header.
*/
#ifndef AVCODEC_AC3ENC_FLOAT_H
#define AVCODEC_AC3ENC_FLOAT_H
#include "fft.h"
typedef float SampleType;
typedef float CoefType;
typedef float CoefSumType;
#define MAC_COEF(d,a,b) ((d)+=(a)*(b))
typedef struct AC3MDCTContext {
const float *window; ///< MDCT window function
FFTContext fft; ///< FFT context for MDCT calculation
} AC3MDCTContext;
#endif /* AVCODEC_AC3ENC_FLOAT_H */