fft-filtering

/*
 * Copyright (c) 2015 Arwa Arif <[email protected]>
 *
 * This file is part of FFmpeg.
 *
 * FFmpeg is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 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 General Public License for more details.
 *
 * You should have received a copy of the GNU 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.
 */

/**
 * @file
 * FFT domain filtering.
 */

#include "libavfilter/internal.h"
#include "libavutil/common.h"
#include "libavutil/imgutils.h"
#include "libavutil/opt.h"
#include "libavutil/pixdesc.h"
#include "libavcodec/avfft.h"

typedef struct {
    const AVClass *class;

    RDFTContext *rdft;
    int rdft_bits;
    FFTSample *rdft_data;

} FFTFILTContext;

static int filter_frame(AVFilterLink *inlink, AVFrame *in)
{
    AVFilterContext *ctx = inlink->dst;
    AVFilterLink *outlink = inlink->dst->outputs[0];
    FFTFILTContext *fftfilt = ctx->priv;
    AVFrame *out;
    int i, rdft_bits;
    size_t rdft_len, w, h;

    w = inlink->w;
    h = inlink->h;

    /* RDFT window size (precision) according to the requested output frame height */
    for (rdft_bits = 1; 1 << rdft_bits < 2 * w; rdft_bits++);
    rdft_len = 1 << rdft_bits;

    fftfilt->rdft_data = av_malloc_array(h, rdft_len);

    for (i = 0; i < h; i++)
        memset(fftfilt->rdft_data, 0, rdft_len * h);

    out = ff_get_video_buffer(outlink, inlink->w, inlink->h);
    if (!out)
        return AVERROR(ENOMEM);

    av_frame_copy_props(out, in);

    /*Horizontal pass - RDFT*/
    for (i = 0; i < h; i++)
        fftfilt->rdft_data[i] = *(in->data[0] + in->linesize[0] * i);

    for (i = 0; i < h; i++)
        av_rdft_calc(fftfilt->rdft, fftfilt->rdft_data + i * rdft_len);

    av_rdft_end(fftfilt->rdft);

    /*Horizontal pass - IRDFT*/
    fftfilt->rdft = av_rdft_init(rdft_bits, IDFT_C2R);

    for (i = 0; i < h; i++)
        av_rdft_calc(fftfilt->rdft, fftfilt->rdft_data + i*rdft_len);

    for (i = 0; i < h; i++)
        *(out->data[0] + out->linesize[0] * i) = fftfilt->rdft_data[i];

    av_rdft_end(fftfilt->rdft);
    av_free(fftfilt->rdft_data);

    av_frame_free(&in);

    return ff_filter_frame(outlink, out);
}

static int query_formats(AVFilterContext *ctx)
{
    static const enum AVPixelFormat pixel_fmts_fftfilt[] = {
        AV_PIX_FMT_GRAY8,
        AV_PIX_FMT_NONE
    };

    ff_set_common_formats(ctx, ff_make_format_list(pixel_fmts_fftfilt));

    return 0;
}

static const AVFilterPad fftfilt_inputs[] = {
    {
        .name = "default",
        .type = AVMEDIA_TYPE_VIDEO,
        .filter_frame = filter_frame,
    },
    { NULL }
};

static const AVFilterPad fftfilt_outputs[] = {
    {
        .name = "default",
        .type = AVMEDIA_TYPE_VIDEO,
    },
    { NULL }
};

AVFilter ff_vf_fftfilt = {
    .name            = "fftfilt",
    .description     = NULL_IF_CONFIG_SMALL("Adjust gain."),
    .priv_size       = sizeof(FFTFILTContext),
  //  .priv_class      = &fftfilt_class,
    .inputs          = fftfilt_inputs,
    .outputs         = fftfilt_outputs,
    .query_formats   = query_formats,
};