libavfilter/af_tremolo.c

   1 /*
   2  * Copyright (c) 2015 Kyle Swanson <k@ylo.ph>.
   3  *
   4  * This file is part of FFmpeg.
   5  *
   6  * FFmpeg is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU Lesser General Public
   8  * License as published by the Free Software Foundation; either
   9  * version 2.1 of the License, or (at your option) any later version.
  10  *
  11  * FFmpeg is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14  * Lesser General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU Lesser General Public
  17  * License along with FFmpeg; if not, write to the Free Software
  18  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  19  */
  20
  21 #include "libavutil/mem.h"
  22 #include "libavutil/opt.h"
  23 #include "avfilter.h"
  24 #include "filters.h"
  25 #include "audio.h"
  26
  27 typedef struct TremoloContext {
  28     const AVClass *class;
  29     double freq;
  30     double depth;
  31     double *table;
  32     int table_size;
  33     int index;
  34 } TremoloContext;
  35
  36 #define OFFSET(x) offsetof(TremoloContext, x)
  37 #define FLAGS AV_OPT_FLAG_AUDIO_PARAM|AV_OPT_FLAG_FILTERING_PARAM
  38
  39 static const AVOption tremolo_options[] = {
  40     { "f", "set frequency in hertz",    OFFSET(freq),    AV_OPT_TYPE_DOUBLE,   {.dbl = 5.0},   0.1,   20000.0, FLAGS },
  41     { "d", "set depth as percentage",   OFFSET(depth),   AV_OPT_TYPE_DOUBLE,   {.dbl = 0.5},   0.0,   1.0,     FLAGS },
  42     { NULL }
  43 };
  44
  45 AVFILTER_DEFINE_CLASS(tremolo);
  46
  47 static int filter_frame(AVFilterLink *inlink, AVFrame *in)
  48 {
  49     AVFilterContext *ctx = inlink->dst;
  50     AVFilterLink *outlink = ctx->outputs[0];
  51     TremoloContext *s = ctx->priv;
  52     const double *src = (const double *)in->data[0];
  53     const int channels = inlink->ch_layout.nb_channels;
  54     const int nb_samples = in->nb_samples;
  55     AVFrame *out;
  56     double *dst;
  57     int n, c;
  58
  59     if (av_frame_is_writable(in)) {
  60         out = in;
  61     } else {
  62         out = ff_get_audio_buffer(outlink, in->nb_samples);
  63         if (!out) {
  64             av_frame_free(&in);
  65             return AVERROR(ENOMEM);
  66         }
  67         av_frame_copy_props(out, in);
  68     }
  69     dst = (double *)out->data[0];
  70
  71     for (n = 0; n < nb_samples; n++) {
  72         for (c = 0; c < channels; c++)
  73             dst[c] = src[c] * s->table[s->index];
  74         dst += channels;
  75         src += channels;
  76         s->index++;
  77         if (s->index >= s->table_size)
  78             s->index = 0;
  79     }
  80
  81     if (in != out)
  82         av_frame_free(&in);
  83
  84     return ff_filter_frame(outlink, out);
  85 }
  86
  87 static av_cold void uninit(AVFilterContext *ctx)
  88 {
  89     TremoloContext *s = ctx->priv;
  90     av_freep(&s->table);
  91 }
  92
  93 static int config_input(AVFilterLink *inlink)
  94 {
  95     AVFilterContext *ctx = inlink->dst;
  96     TremoloContext *s = ctx->priv;
  97     const double offset = 1. - s->depth / 2.;
  98     int i;
  99
 100     s->table_size = lrint(inlink->sample_rate / s->freq + 0.5);
 101     s->table = av_malloc_array(s->table_size, sizeof(*s->table));
 102     if (!s->table)
 103         return AVERROR(ENOMEM);
 104
 105     for (i = 0; i < s->table_size; i++) {
 106         double env = s->freq * i / inlink->sample_rate;
 107         env = sin(2 * M_PI * fmod(env + 0.25, 1.0));
 108         s->table[i] = env * (1 - fabs(offset)) + offset;
 109     }
 110
 111     s->index = 0;
 112
 113     return 0;
 114 }
 115
 116 static const AVFilterPad avfilter_af_tremolo_inputs[] = {
 117     {
 118         .name         = "default",
 119         .type         = AVMEDIA_TYPE_AUDIO,
 120         .config_props = config_input,
 121         .filter_frame = filter_frame,
 122     },
 123 };
 124
 125 const FFFilter ff_af_tremolo = {
 126     .p.name        = "tremolo",
 127     .p.description = NULL_IF_CONFIG_SMALL("Apply tremolo effect."),
 128     .p.priv_class  = &tremolo_class,
 129     .p.flags       = AVFILTER_FLAG_SUPPORT_TIMELINE_GENERIC,
 130     .priv_size     = sizeof(TremoloContext),
 131     .uninit        = uninit,
 132     FILTER_INPUTS(avfilter_af_tremolo_inputs),
 133     FILTER_OUTPUTS(ff_audio_default_filterpad),
 134     FILTER_SINGLE_SAMPLEFMT(AV_SAMPLE_FMT_DBL),
 135 };