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af_earwax.c
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1 /*
2  * Copyright (c) 2011 Mina Nagy Zaki
3  * Copyright (c) 2000 Edward Beingessner And Sundry Contributors.
4  * This source code is freely redistributable and may be used for any purpose.
5  * This copyright notice must be maintained. Edward Beingessner And Sundry
6  * Contributors are not responsible for the consequences of using this
7  * software.
8  *
9  * This file is part of FFmpeg.
10  *
11  * FFmpeg is free software; you can redistribute it and/or
12  * modify it under the terms of the GNU Lesser General Public
13  * License as published by the Free Software Foundation; either
14  * version 2.1 of the License, or (at your option) any later version.
15  *
16  * FFmpeg is distributed in the hope that it will be useful,
17  * but WITHOUT ANY WARRANTY; without even the implied warranty of
18  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
19  * Lesser General Public License for more details.
20  *
21  * You should have received a copy of the GNU Lesser General Public
22  * License along with FFmpeg; if not, write to the Free Software
23  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
24  */
25 
26 /**
27  * @file
28  * Stereo Widening Effect. Adds audio cues to move stereo image in
29  * front of the listener. Adapted from the libsox earwax effect.
30  */
31 
33 #include "avfilter.h"
34 #include "audio.h"
35 #include "formats.h"
36 
37 #define NUMTAPS 64
38 
39 static const int8_t filt[NUMTAPS] = {
40 /* 30° 330° */
41  4, -6, /* 32 tap stereo FIR filter. */
42  4, -11, /* One side filters as if the */
43  -1, -5, /* signal was from 30 degrees */
44  3, 3, /* from the ear, the other as */
45  -2, 5, /* if 330 degrees. */
46  -5, 0,
47  9, 1,
48  6, 3, /* Input */
49  -4, -1, /* Left Right */
50  -5, -3, /* __________ __________ */
51  -2, -5, /* | | | | */
52  -7, 1, /* .---| Hh,0(f) | | Hh,0(f) |---. */
53  6, -7, /* / |__________| |__________| \ */
54  30, -29, /* / \ / \ */
55  12, -3, /* / X \ */
56  -11, 4, /* / / \ \ */
57  -3, 7, /* ____V_____ __________V V__________ _____V____ */
58  -20, 23, /* | | | | | | | | */
59  2, 0, /* | Hh,30(f) | | Hh,330(f)| | Hh,330(f)| | Hh,30(f) | */
60  1, -6, /* |__________| |__________| |__________| |__________| */
61  -14, -5, /* \ ___ / \ ___ / */
62  15, -18, /* \ / \ / _____ \ / \ / */
63  6, 7, /* `->| + |<--' / \ `-->| + |<-' */
64  15, -10, /* \___/ _/ \_ \___/ */
65  -14, 22, /* \ / \ / \ / */
66  -7, -2, /* `--->| | | |<---' */
67  -4, 9, /* \_/ \_/ */
68  6, -12, /* */
69  6, -6, /* Headphones */
70  0, -11,
71  0, -5,
72  4, 0};
73 
74 typedef struct {
75  int16_t taps[NUMTAPS * 2];
77 
79 {
80  static const int sample_rates[] = { 44100, -1 };
81 
84 
86  ff_set_common_formats(ctx, formats);
88  ff_set_common_channel_layouts(ctx, layout);
90 
91  return 0;
92 }
93 
94 //FIXME: replace with DSPContext.scalarproduct_int16
95 static inline int16_t *scalarproduct(const int16_t *in, const int16_t *endin, int16_t *out)
96 {
98  int16_t j;
99 
100  while (in < endin) {
101  sample = 32;
102  for (j = 0; j < NUMTAPS; j++)
103  sample += in[j] * filt[j];
104  *out = sample >> 6;
105  out++;
106  in++;
107  }
108 
109  return out;
110 }
111 
112 static int filter_frame(AVFilterLink *inlink, AVFilterBufferRef *insamples)
113 {
114  AVFilterLink *outlink = inlink->dst->outputs[0];
115  int16_t *taps, *endin, *in, *out;
116  AVFilterBufferRef *outsamples =
118  insamples->audio->nb_samples);
119  int ret;
120 
121  if (!outsamples)
122  return AVERROR(ENOMEM);
123  avfilter_copy_buffer_ref_props(outsamples, insamples);
124 
125  taps = ((EarwaxContext *)inlink->dst->priv)->taps;
126  out = (int16_t *)outsamples->data[0];
127  in = (int16_t *)insamples ->data[0];
128 
129  // copy part of new input and process with saved input
130  memcpy(taps+NUMTAPS, in, NUMTAPS * sizeof(*taps));
131  out = scalarproduct(taps, taps + NUMTAPS, out);
132 
133  // process current input
134  endin = in + insamples->audio->nb_samples * 2 - NUMTAPS;
135  scalarproduct(in, endin, out);
136 
137  // save part of input for next round
138  memcpy(taps, endin, NUMTAPS * sizeof(*taps));
139 
140  ret = ff_filter_frame(outlink, outsamples);
141  avfilter_unref_buffer(insamples);
142  return ret;
143 }
144 
145 static const AVFilterPad earwax_inputs[] = {
146  {
147  .name = "default",
148  .type = AVMEDIA_TYPE_AUDIO,
149  .filter_frame = filter_frame,
150  .min_perms = AV_PERM_READ,
151  },
152  { NULL }
153 };
154 
155 static const AVFilterPad earwax_outputs[] = {
156  {
157  .name = "default",
158  .type = AVMEDIA_TYPE_AUDIO,
159  },
160  { NULL }
161 };
162 
164  .name = "earwax",
165  .description = NULL_IF_CONFIG_SMALL("Widen the stereo image."),
166  .query_formats = query_formats,
167  .priv_size = sizeof(EarwaxContext),
168  .inputs = earwax_inputs,
169  .outputs = earwax_outputs,
170 };