FFmpeg/libavfilter/vf_vflip.c

/*
 * Copyright (c) 2007 Bobby Bingham
 *
 * 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
 */

/**
 * @file
 * video vertical flip filter
 */

#include "libavutil/internal.h"
#include "libavutil/pixdesc.h"
#include "avfilter.h"
#include "internal.h"
#include "video.h"

typedef struct FlipContext {
    int vsub;   ///< vertical chroma subsampling
} FlipContext;

static int config_input(AVFilterLink *link)
{
    FlipContext *flip = link->dst->priv;
    const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(link->format);

    flip->vsub = desc->log2_chroma_h;

    return 0;
}

static AVFrame *get_video_buffer(AVFilterLink *link, int w, int h)
{
    FlipContext *flip = link->dst->priv;
    AVFrame *frame;
    int i;

    frame = ff_get_video_buffer(link->dst->outputs[0], w, h);
    if (!frame)
        return NULL;

    for (i = 0; i < 4; i ++) {
        int vsub = i == 1 || i == 2 ? flip->vsub : 0;
        int height = AV_CEIL_RSHIFT(h, vsub);

        if (frame->data[i]) {
            frame->data[i] += (height - 1) * frame->linesize[i];
            frame->linesize[i] = -frame->linesize[i];
        }
    }

    return frame;
}

static int filter_frame(AVFilterLink *link, AVFrame *frame)
{
    FlipContext *flip = link->dst->priv;
    int i;

    for (i = 0; i < 4; i ++) {
        int vsub = i == 1 || i == 2 ? flip->vsub : 0;
        int height = AV_CEIL_RSHIFT(link->h, vsub);

        if (frame->data[i]) {
            frame->data[i] += (height - 1) * frame->linesize[i];
            frame->linesize[i] = -frame->linesize[i];
        }
    }

    return ff_filter_frame(link->dst->outputs[0], frame);
}
static const AVFilterPad avfilter_vf_vflip_inputs[] = {
    {
        .name             = "default",
        .type             = AVMEDIA_TYPE_VIDEO,
        .get_video_buffer = get_video_buffer,
        .filter_frame     = filter_frame,
        .config_props     = config_input,
    },
    { NULL }
};

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

AVFilter ff_vf_vflip = {
    .name        = "vflip",
    .description = NULL_IF_CONFIG_SMALL("Flip the input video vertically."),
    .priv_size   = sizeof(FlipContext),
    .inputs      = avfilter_vf_vflip_inputs,
    .outputs     = avfilter_vf_vflip_outputs,
};