2 * Header file for hardcoded DSD tables
3 * based on BSD licensed dsd2pcm by Sebastian Gesemann
4 * Copyright (c) 2009, 2011 Sebastian Gesemann. All rights reserved.
6 * This file is part of FFmpeg.
8 * FFmpeg is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU Lesser General Public
10 * License as published by the Free Software Foundation; either
11 * version 2.1 of the License, or (at your option) any later version.
13 * FFmpeg is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 * Lesser General Public License for more details.
18 * You should have received a copy of the GNU Lesser General Public
19 * License along with FFmpeg; if not, write to the Free Software
20 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
23 #ifndef AVCODEC_DSD_TABLEGEN_H
24 #define AVCODEC_DSD_TABLEGEN_H
27 #include "libavutil/attributes.h"
29 #define HTAPS 48 /** number of FIR constants */
30 #define CTABLES ((HTAPS + 7) / 8) /** number of "8 MACs" lookup tables */
32 #if CONFIG_HARDCODED_TABLES
33 #define dsd_ctables_tableinit()
34 #include "libavcodec/dsd_tables.h"
36 #include "libavutil/common.h"
39 * Properties of this 96-tap lowpass filter when applied on a signal
40 * with sampling rate of 44100*64 Hz:
42 * () has a delay of 17 microseconds.
44 * () flat response up to 48 kHz
46 * () if you downsample afterwards by a factor of 8, the
47 * spectrum below 70 kHz is practically alias-free.
49 * () stopband rejection is about 160 dB
51 * The coefficient tables ("ctables") take only 6 Kibi Bytes and
52 * should fit into a modern processor's fast cache.
56 * The 2nd half (48 coeffs) of a 96-tap symmetric lowpass filter
58 static const double htaps
[HTAPS
] = {
59 0.09950731974056658, 0.09562845727714668, 0.08819647126516944,
60 0.07782552527068175, 0.06534876523171299, 0.05172629311427257,
61 0.0379429484910187, 0.02490921351762261, 0.0133774746265897,
62 0.003883043418804416, -0.003284703416210726, -0.008080250212687497,
63 -0.01067241812471033, -0.01139427235000863, -0.0106813877974587,
64 -0.009007905078766049, -0.006828859761015335, -0.004535184322001496,
65 -0.002425035959059578, -0.0006922187080790708, 0.0005700762133516592,
66 0.001353838005269448, 0.001713709169690937, 0.001742046839472948,
67 0.001545601648013235, 0.001226696225277855, 0.0008704322683580222,
68 0.0005381636200535649, 0.000266446345425276, 7.002968738383528e-05,
69 -5.279407053811266e-05, -0.0001140625650874684, -0.0001304796361231895,
70 -0.0001189970287491285, -9.396247155265073e-05, -6.577634378272832e-05,
71 -4.07492895872535e-05, -2.17407957554587e-05, -9.163058931391722e-06,
72 -2.017460145032201e-06, 1.249721855219005e-06, 2.166655190537392e-06,
73 1.930520892991082e-06, 1.319400334374195e-06, 7.410039764949091e-07,
74 3.423230509967409e-07, 1.244182214744588e-07, 3.130441005359396e-08
77 static float ctables
[CTABLES
][256];
79 static av_cold
void dsd_ctables_tableinit(void)
83 for (t
= 0; t
< CTABLES
; ++t
) {
84 k
= FFMIN(HTAPS
- t
* 8, 8);
85 for (e
= 0; e
< 256; ++e
) {
87 for (m
= 0; m
< k
; ++m
)
88 acc
+= (((e
>> (7 - m
)) & 1) * 2 - 1) * htaps
[t
* 8 + m
];
89 ctables
[CTABLES
- 1 - t
][e
] = (float)acc
;
93 #endif /* CONFIG_HARDCODED_TABLES */
95 #endif /* AVCODEC_DSD_TABLEGEN_H */