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https://github.com/FFmpeg/FFmpeg.git
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134dba9544
xHE-AAC relies on the same postfilter mechanism that Opus uses to improve clarity (albeit with a steeper deemphasis filter). The code to apply it is identical, it's still just a simple IIR low-pass filter. This commit makes it possible to use alternative constants.
69 lines
1.9 KiB
C
69 lines
1.9 KiB
C
/*
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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 "config.h"
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#include "libavutil/attributes.h"
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#include "libavutil/mem_internal.h"
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#include "opusdsp.h"
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static void postfilter_c(float *data, int period, float *gains, int len)
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{
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const float g0 = gains[0];
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const float g1 = gains[1];
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const float g2 = gains[2];
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float x4 = data[-period - 2];
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float x3 = data[-period - 1];
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float x2 = data[-period + 0];
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float x1 = data[-period + 1];
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for (int i = 0; i < len; i++) {
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float x0 = data[i - period + 2];
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data[i] += g0 * x2 +
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g1 * (x1 + x3) +
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g2 * (x0 + x4);
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x4 = x3;
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x3 = x2;
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x2 = x1;
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x1 = x0;
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}
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}
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static float deemphasis_c(float *y, float *x, float coeff, const float *weights, int len)
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{
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const float c = weights[0];
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for (int i = 0; i < len; i++)
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coeff = y[i] = x[i] + coeff*c;
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return coeff;
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}
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av_cold void ff_opus_dsp_init(OpusDSP *ctx)
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{
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ctx->postfilter = postfilter_c;
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ctx->deemphasis = deemphasis_c;
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#if ARCH_AARCH64
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ff_opus_dsp_init_aarch64(ctx);
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#elif ARCH_RISCV
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ff_opus_dsp_init_riscv(ctx);
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#elif ARCH_X86
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ff_opus_dsp_init_x86(ctx);
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#endif
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}
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