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95 lines
3.5 KiB
95 lines
3.5 KiB
/* |
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* Header file for hardcoded DSD tables |
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* based on BSD licensed dsd2pcm by Sebastian Gesemann |
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* Copyright (c) 2009, 2011 Sebastian Gesemann. All rights reserved. |
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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_DSD_TABLEGEN_H |
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#define AVCODEC_DSD_TABLEGEN_H |
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#include <stdint.h> |
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#include "libavutil/attributes.h" |
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#define HTAPS 48 /** number of FIR constants */ |
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#define CTABLES ((HTAPS + 7) / 8) /** number of "8 MACs" lookup tables */ |
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#if CONFIG_HARDCODED_TABLES |
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#define dsd_ctables_tableinit() |
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#include "libavcodec/dsd_tables.h" |
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#else |
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#include "libavutil/common.h" |
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/* |
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* Properties of this 96-tap lowpass filter when applied on a signal |
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* with sampling rate of 44100*64 Hz: |
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* |
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* () has a delay of 17 microseconds. |
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* |
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* () flat response up to 48 kHz |
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* |
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* () if you downsample afterwards by a factor of 8, the |
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* spectrum below 70 kHz is practically alias-free. |
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* |
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* () stopband rejection is about 160 dB |
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* |
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* The coefficient tables ("ctables") take only 6 Kibi Bytes and |
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* should fit into a modern processor's fast cache. |
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*/ |
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/** |
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* The 2nd half (48 coeffs) of a 96-tap symmetric lowpass filter |
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*/ |
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static const double htaps[HTAPS] = { |
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0.09950731974056658, 0.09562845727714668, 0.08819647126516944, |
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0.07782552527068175, 0.06534876523171299, 0.05172629311427257, |
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0.0379429484910187, 0.02490921351762261, 0.0133774746265897, |
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0.003883043418804416, -0.003284703416210726, -0.008080250212687497, |
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-0.01067241812471033, -0.01139427235000863, -0.0106813877974587, |
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-0.009007905078766049, -0.006828859761015335, -0.004535184322001496, |
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-0.002425035959059578, -0.0006922187080790708, 0.0005700762133516592, |
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0.001353838005269448, 0.001713709169690937, 0.001742046839472948, |
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0.001545601648013235, 0.001226696225277855, 0.0008704322683580222, |
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0.0005381636200535649, 0.000266446345425276, 7.002968738383528e-05, |
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-5.279407053811266e-05, -0.0001140625650874684, -0.0001304796361231895, |
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-0.0001189970287491285, -9.396247155265073e-05, -6.577634378272832e-05, |
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-4.07492895872535e-05, -2.17407957554587e-05, -9.163058931391722e-06, |
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-2.017460145032201e-06, 1.249721855219005e-06, 2.166655190537392e-06, |
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1.930520892991082e-06, 1.319400334374195e-06, 7.410039764949091e-07, |
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3.423230509967409e-07, 1.244182214744588e-07, 3.130441005359396e-08 |
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}; |
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static float ctables[CTABLES][256]; |
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static av_cold void dsd_ctables_tableinit(void) |
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{ |
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int t, e, m, k; |
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double acc; |
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for (t = 0; t < CTABLES; ++t) { |
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k = FFMIN(HTAPS - t * 8, 8); |
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for (e = 0; e < 256; ++e) { |
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acc = 0.0; |
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for (m = 0; m < k; ++m) |
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acc += (((e >> (7 - m)) & 1) * 2 - 1) * htaps[t * 8 + m]; |
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ctables[CTABLES - 1 - t][e] = (float)acc; |
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} |
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} |
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} |
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#endif /* CONFIG_HARDCODED_TABLES */ |
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#endif /* AVCODEC_DSD_TABLEGEN_H */
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