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https://github.com/FFmpeg/FFmpeg.git
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64ab577954
To avoid data dependencies, this does the following unroll, which
requires one extra but probably free addition:
coeff = (b * left_weight) >> decorr_shift;
b += a;
a -= coeff;
b -= coeff;
swap(a, b);
67 lines
1.9 KiB
C
67 lines
1.9 KiB
C
/*
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* ALAC (Apple Lossless Audio Codec) decoder
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* Copyright (c) 2005 David Hammerton
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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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#include "libavutil/attributes.h"
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#include "alacdsp.h"
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#include "config.h"
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static void decorrelate_stereo(int32_t *buffer[2], int nb_samples,
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int decorr_shift, int decorr_left_weight)
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{
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int i;
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for (i = 0; i < nb_samples; i++) {
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uint32_t a, b;
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a = buffer[0][i];
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b = buffer[1][i];
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a -= (int)(b * decorr_left_weight) >> decorr_shift;
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b += a;
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buffer[0][i] = b;
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buffer[1][i] = a;
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}
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}
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static void append_extra_bits(int32_t *buffer[2], int32_t *extra_bits_buffer[2],
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int extra_bits, int channels, int nb_samples)
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{
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int i, ch;
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for (ch = 0; ch < channels; ch++)
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for (i = 0; i < nb_samples; i++)
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buffer[ch][i] = ((unsigned)buffer[ch][i] << extra_bits) | extra_bits_buffer[ch][i];
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}
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av_cold void ff_alacdsp_init(ALACDSPContext *c)
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{
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c->decorrelate_stereo = decorrelate_stereo;
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c->append_extra_bits[0] =
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c->append_extra_bits[1] = append_extra_bits;
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#if ARCH_RISCV
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ff_alacdsp_init_riscv(c);
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#elif ARCH_X86
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ff_alacdsp_init_x86(c);
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#endif
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}
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