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