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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.  
  32. #include "libavutil/channel_layout.h"
  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];
  76. } EarwaxContext;
  77.  
  78. static int query_formats(AVFilterContext *ctx)
  79. {
  80.     static const int sample_rates[] = { 44100, -1 };
  81.  
  82.     AVFilterFormats *formats = NULL;
  83.     AVFilterChannelLayouts *layout = NULL;
  84.  
  85.     ff_add_format(&formats, AV_SAMPLE_FMT_S16);
  86.     ff_set_common_formats(ctx, formats);
  87.     ff_add_channel_layout(&layout, AV_CH_LAYOUT_STEREO);
  88.     ff_set_common_channel_layouts(ctx, layout);
  89.     ff_set_common_samplerates(ctx, ff_make_format_list(sample_rates));
  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. {
  97.     int32_t sample;
  98.     int16_t j;
  99.  
  100.     while (in < endin) {
  101.         sample = 0;
  102.         for (j = 0; j < NUMTAPS; j++)
  103.             sample += in[j] * filt[j];
  104.         *out = av_clip_int16(sample >> 6);
  105.         out++;
  106.         in++;
  107.     }
  108.  
  109.     return out;
  110. }
  111.  
  112. static int filter_frame(AVFilterLink *inlink, AVFrame *insamples)
  113. {
  114.     AVFilterLink *outlink = inlink->dst->outputs[0];
  115.     int16_t *taps, *endin, *in, *out;
  116.     AVFrame *outsamples = ff_get_audio_buffer(inlink, insamples->nb_samples);
  117.     int len;
  118.  
  119.     if (!outsamples) {
  120.         av_frame_free(&insamples);
  121.         return AVERROR(ENOMEM);
  122.     }
  123.     av_frame_copy_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.     len = FFMIN(NUMTAPS, 2*insamples->nb_samples);
  130.     // copy part of new input and process with saved input
  131.     memcpy(taps+NUMTAPS, in, len * sizeof(*taps));
  132.     out   = scalarproduct(taps, taps + len, out);
  133.  
  134.     // process current input
  135.     if (2*insamples->nb_samples >= NUMTAPS ){
  136.         endin = in + insamples->nb_samples * 2 - NUMTAPS;
  137.         scalarproduct(in, endin, out);
  138.  
  139.         // save part of input for next round
  140.         memcpy(taps, endin, NUMTAPS * sizeof(*taps));
  141.     } else
  142.         memmove(taps, taps + 2*insamples->nb_samples, NUMTAPS * sizeof(*taps));
  143.  
  144.     av_frame_free(&insamples);
  145.     return ff_filter_frame(outlink, outsamples);
  146. }
  147.  
  148. static const AVFilterPad earwax_inputs[] = {
  149.     {
  150.         .name         = "default",
  151.         .type         = AVMEDIA_TYPE_AUDIO,
  152.         .filter_frame = filter_frame,
  153.     },
  154.     { NULL }
  155. };
  156.  
  157. static const AVFilterPad earwax_outputs[] = {
  158.     {
  159.         .name = "default",
  160.         .type = AVMEDIA_TYPE_AUDIO,
  161.     },
  162.     { NULL }
  163. };
  164.  
  165. AVFilter avfilter_af_earwax = {
  166.     .name           = "earwax",
  167.     .description    = NULL_IF_CONFIG_SMALL("Widen the stereo image."),
  168.     .query_formats  = query_formats,
  169.     .priv_size      = sizeof(EarwaxContext),
  170.     .inputs         = earwax_inputs,
  171.     .outputs        = earwax_outputs,
  172. };
  173.