/* * Copyright (c) 2000 Chris Ausbrooks <weed@bucket.pp.ualr.edu> * Copyright (c) 2000 Fabien COELHO <fabien@coelho.net> * * This file is part of FFmpeg. * * FFmpeg is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public * License as published by the Free Software Foundation; either * version 2.1 of the License, or (at your option) any later version. * * FFmpeg is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with FFmpeg; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA */ #include "libavutil/opt.h"#include "libavutil/samplefmt.h"#include "avfilter.h"#include "audio.h"#include "internal.h" typedef struct DCShiftContext {    const AVClass *class;    double dcshift;    double limiterthreshold;    double limitergain;} DCShiftContext; #define OFFSET(x) offsetof(DCShiftContext, x)#define A AV_OPT_FLAG_AUDIO_PARAM|AV_OPT_FLAG_FILTERING_PARAM static const AVOption dcshift_options[] = {    { "shift",       "set DC shift",     OFFSET(dcshift),       AV_OPT_TYPE_DOUBLE, {.dbl=0}, -1, 1, A },    { "limitergain", "set limiter gain", OFFSET(limitergain), AV_OPT_TYPE_DOUBLE, {.dbl=0}, 0, 1, A },    { NULL }}; AVFILTER_DEFINE_CLASS(dcshift); static av_cold int init(AVFilterContext *ctx){    DCShiftContext *s = ctx->priv;     s->limiterthreshold = INT32_MAX * (1.0 - (fabs(s->dcshift) - s->limitergain));     return 0;} static int filter_frame(AVFilterLink *inlink, AVFrame *in){    AVFilterContext *ctx = inlink->dst;    AVFilterLink *outlink = ctx->outputs[0];    AVFrame *out;    DCShiftContext *s = ctx->priv;    int i, j;    double dcshift = s->dcshift;     if (av_frame_is_writable(in)) {        out = in;    } else {        out = ff_get_audio_buffer(outlink, in->nb_samples);        if (!out) {            av_frame_free(&in);            return AVERROR(ENOMEM);        }        av_frame_copy_props(out, in);    }     if (s->limitergain > 0) {        for (i = 0; i < inlink->ch_layout.nb_channels; i++) {            const int32_t *src = (int32_t *)in->extended_data[i];            int32_t *dst = (int32_t *)out->extended_data[i];             for (j = 0; j < in->nb_samples; j++) {                double d;                 d = src[j];                 if (d > s->limiterthreshold && dcshift > 0) {                    d = (d - s->limiterthreshold) * s->limitergain /                             (INT32_MAX - s->limiterthreshold) +                             s->limiterthreshold + dcshift;                } else if (d < -s->limiterthreshold && dcshift < 0) {                    d = (d + s->limiterthreshold) * s->limitergain /                             (INT32_MAX - s->limiterthreshold) -                             s->limiterthreshold + dcshift;                } else {                    d = dcshift * INT32_MAX + d;                }                 dst[j] = av_clipl_int32(d);            }        }    } else {        for (i = 0; i < inlink->ch_layout.nb_channels; i++) {            const int32_t *src = (int32_t *)in->extended_data[i];            int32_t *dst = (int32_t *)out->extended_data[i];             for (j = 0; j < in->nb_samples; j++) {                double d = dcshift * (INT32_MAX + 1.) + src[j];                 dst[j] = av_clipl_int32(d);            }        }    }     if (out != in)        av_frame_free(&in);    return ff_filter_frame(outlink, out);}static const AVFilterPad dcshift_inputs[] = {    {        .name         = "default",        .type         = AVMEDIA_TYPE_AUDIO,        .filter_frame = filter_frame,    },}; static const AVFilterPad dcshift_outputs[] = {    {        .name = "default",        .type = AVMEDIA_TYPE_AUDIO,    },}; const AVFilter ff_af_dcshift = {    .name           = "dcshift",    .description    = NULL_IF_CONFIG_SMALL("Apply a DC shift to the audio."),    .priv_size      = sizeof(DCShiftContext),    .priv_class     = &dcshift_class,    .init           = init,    FILTER_INPUTS(dcshift_inputs),    FILTER_OUTPUTS(dcshift_outputs),    FILTER_SINGLE_SAMPLEFMT(AV_SAMPLE_FMT_S32P),    .flags          = AVFILTER_FLAG_SUPPORT_TIMELINE_GENERIC,};