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  1. /*
  2.  * Copyright (c) 2000 Chris Ausbrooks <weed@bucket.pp.ualr.edu>
  3.  * Copyright (c) 2000 Fabien COELHO <fabien@coelho.net>
  4.  *
  5.  * This file is part of FFmpeg.
  6.  *
  7.  * FFmpeg is free software; you can redistribute it and/or
  8.  * modify it under the terms of the GNU Lesser General Public
  9.  * License as published by the Free Software Foundation; either
  10.  * version 2.1 of the License, or (at your option) any later version.
  11.  *
  12.  * FFmpeg is distributed in the hope that it will be useful,
  13.  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14.  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15.  * Lesser General Public License for more details.
  16.  *
  17.  * You should have received a copy of the GNU Lesser General Public
  18.  * License along with FFmpeg; if not, write to the Free Software
  19.  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  20.  */
  21.  
  22. #include "libavutil/opt.h"
  23. #include "libavutil/samplefmt.h"
  24. #include "avfilter.h"
  25. #include "audio.h"
  26. #include "internal.h"
  27.  
  28. typedef struct DCShiftContext {
  29.     const AVClass *class;
  30.     double dcshift;
  31.     double limiterthreshhold;
  32.     double limitergain;
  33. } DCShiftContext;
  34.  
  35. #define OFFSET(x) offsetof(DCShiftContext, x)
  36. #define A AV_OPT_FLAG_AUDIO_PARAM|AV_OPT_FLAG_FILTERING_PARAM
  37.  
  38. static const AVOption dcshift_options[] = {
  39.     { "shift",       "set DC shift",     OFFSET(dcshift),       AV_OPT_TYPE_DOUBLE, {.dbl=0}, -1, 1, A },
  40.     { "limitergain", "set limiter gain", OFFSET(limitergain), AV_OPT_TYPE_DOUBLE, {.dbl=0}, 0, 1, A },
  41.     { NULL }
  42. };
  43.  
  44. AVFILTER_DEFINE_CLASS(dcshift);
  45.  
  46. static av_cold int init(AVFilterContext *ctx)
  47. {
  48.     DCShiftContext *s = ctx->priv;
  49.  
  50.     s->limiterthreshhold = INT32_MAX * (1.0 - (fabs(s->dcshift) - s->limitergain));
  51.  
  52.     return 0;
  53. }
  54.  
  55. static int query_formats(AVFilterContext *ctx)
  56. {
  57.     AVFilterChannelLayouts *layouts;
  58.     AVFilterFormats *formats;
  59.     static const enum AVSampleFormat sample_fmts[] = {
  60.         AV_SAMPLE_FMT_S32P, AV_SAMPLE_FMT_NONE
  61.     };
  62.     int ret;
  63.  
  64.     layouts = ff_all_channel_layouts();
  65.     if (!layouts)
  66.         return AVERROR(ENOMEM);
  67.     ret = ff_set_common_channel_layouts(ctx, layouts);
  68.     if (ret < 0)
  69.         return ret;
  70.  
  71.     formats = ff_make_format_list(sample_fmts);
  72.     if (!formats)
  73.         return AVERROR(ENOMEM);
  74.     ret = ff_set_common_formats(ctx, formats);
  75.     if (ret < 0)
  76.         return ret;
  77.  
  78.     formats = ff_all_samplerates();
  79.     if (!formats)
  80.         return AVERROR(ENOMEM);
  81.     return ff_set_common_samplerates(ctx, formats);
  82. }
  83.  
  84. static int filter_frame(AVFilterLink *inlink, AVFrame *in)
  85. {
  86.     AVFilterContext *ctx = inlink->dst;
  87.     AVFilterLink *outlink = ctx->outputs[0];
  88.     AVFrame *out = ff_get_audio_buffer(inlink, in->nb_samples);
  89.     DCShiftContext *s = ctx->priv;
  90.     int i, j;
  91.     double dcshift = s->dcshift;
  92.  
  93.     if (!out) {
  94.         av_frame_free(&in);
  95.         return AVERROR(ENOMEM);
  96.     }
  97.     av_frame_copy_props(out, in);
  98.  
  99.     if (s->limitergain > 0) {
  100.         for (i = 0; i < inlink->channels; i++) {
  101.             const int32_t *src = (int32_t *)in->extended_data[i];
  102.             int32_t *dst = (int32_t *)out->extended_data[i];
  103.  
  104.             for (j = 0; j < in->nb_samples; j++) {
  105.                 double d;
  106.  
  107.                 d = src[j];
  108.  
  109.                 if (d > s->limiterthreshhold && dcshift > 0) {
  110.                     d = (d - s->limiterthreshhold) * s->limitergain /
  111.                              (INT32_MAX - s->limiterthreshhold) +
  112.                              s->limiterthreshhold + dcshift;
  113.                 } else if (d < -s->limiterthreshhold && dcshift < 0) {
  114.                     d = (d + s->limiterthreshhold) * s->limitergain /
  115.                              (INT32_MAX - s->limiterthreshhold) -
  116.                              s->limiterthreshhold + dcshift;
  117.                 } else {
  118.                     d = dcshift * INT32_MAX + d;
  119.                 }
  120.  
  121.                 dst[j] = av_clipl_int32(d);
  122.             }
  123.         }
  124.     } else {
  125.         for (i = 0; i < inlink->channels; i++) {
  126.             const int32_t *src = (int32_t *)in->extended_data[i];
  127.             int32_t *dst = (int32_t *)out->extended_data[i];
  128.  
  129.             for (j = 0; j < in->nb_samples; j++) {
  130.                 double d = dcshift * (INT32_MAX + 1.) + src[j];
  131.  
  132.                 dst[j] = av_clipl_int32(d);
  133.             }
  134.         }
  135.     }
  136.  
  137.     av_frame_free(&in);
  138.     return ff_filter_frame(outlink, out);
  139. }
  140. static const AVFilterPad dcshift_inputs[] = {
  141.     {
  142.         .name         = "default",
  143.         .type         = AVMEDIA_TYPE_AUDIO,
  144.         .filter_frame = filter_frame,
  145.     },
  146.     { NULL }
  147. };
  148.  
  149. static const AVFilterPad dcshift_outputs[] = {
  150.     {
  151.         .name = "default",
  152.         .type = AVMEDIA_TYPE_AUDIO,
  153.     },
  154.     { NULL }
  155. };
  156.  
  157. AVFilter ff_af_dcshift = {
  158.     .name           = "dcshift",
  159.     .description    = NULL_IF_CONFIG_SMALL("Apply a DC shift to the audio."),
  160.     .query_formats  = query_formats,
  161.     .priv_size      = sizeof(DCShiftContext),
  162.     .priv_class     = &dcshift_class,
  163.     .init           = init,
  164.     .inputs         = dcshift_inputs,
  165.     .outputs        = dcshift_outputs,
  166.     .flags          = AVFILTER_FLAG_SUPPORT_TIMELINE_GENERIC,
  167. };
  168.