FFmpeg/libavfilter/vf_fade.c

/*
 * Copyright (c) 2010 Brandon Mintern
 * Copyright (c) 2007 Bobby Bingham
 *
 * This file is part of Libav.
 *
 * Libav 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.
 *
 * Libav 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 Libav; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

/**
 * @file
 * video fade filter
 * based heavily on vf_negate.c by Bobby Bingham
 */

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

typedef struct {
    int factor, fade_per_frame;
    unsigned int frame_index, start_frame, stop_frame;
    int hsub, vsub, bpp;
} FadeContext;

static av_cold int init(AVFilterContext *ctx, const char *args, void *opaque)
{
    FadeContext *fade = ctx->priv;
    unsigned int nb_frames;
    char in_out[4];

    if (!args ||
        sscanf(args, " %3[^:]:%u:%u", in_out, &fade->start_frame, &nb_frames) != 3) {
        av_log(ctx, AV_LOG_ERROR,
               "Expected 3 arguments '(in|out):#:#':'%s'\n", args);
        return AVERROR(EINVAL);
    }

    nb_frames = nb_frames ? nb_frames : 1;
    fade->fade_per_frame = (1 << 16) / nb_frames;
    if (!strcmp(in_out, "in"))
        fade->factor = 0;
    else if (!strcmp(in_out, "out")) {
        fade->fade_per_frame = -fade->fade_per_frame;
        fade->factor = (1 << 16);
    } else {
        av_log(ctx, AV_LOG_ERROR,
               "first argument must be 'in' or 'out':'%s'\n", in_out);
        return AVERROR(EINVAL);
    }
    fade->stop_frame = fade->start_frame + nb_frames;

    av_log(ctx, AV_LOG_INFO,
           "type:%s start_frame:%d nb_frames:%d\n",
           in_out, fade->start_frame, nb_frames);
    return 0;
}

static int query_formats(AVFilterContext *ctx)
{
    static const enum PixelFormat pix_fmts[] = {
        PIX_FMT_YUV444P,  PIX_FMT_YUV422P,  PIX_FMT_YUV420P,
        PIX_FMT_YUV411P,  PIX_FMT_YUV410P,
        PIX_FMT_YUVJ444P, PIX_FMT_YUVJ422P, PIX_FMT_YUVJ420P,
        PIX_FMT_YUV440P,  PIX_FMT_YUVJ440P,
        PIX_FMT_RGB24,    PIX_FMT_BGR24,
        PIX_FMT_NONE
    };

    avfilter_set_common_formats(ctx, avfilter_make_format_list(pix_fmts));
    return 0;
}

static int config_props(AVFilterLink *inlink)
{
    FadeContext *fade = inlink->dst->priv;
    const AVPixFmtDescriptor *pixdesc = &av_pix_fmt_descriptors[inlink->format];

    fade->hsub = pixdesc->log2_chroma_w;
    fade->vsub = pixdesc->log2_chroma_h;

    fade->bpp = av_get_bits_per_pixel(pixdesc) >> 3;
    return 0;
}

static void draw_slice(AVFilterLink *inlink, int y, int h, int slice_dir)
{
    FadeContext *fade = inlink->dst->priv;
    AVFilterBufferRef *outpic = inlink->cur_buf;
    uint8_t *p;
    int i, j, plane;

    if (fade->factor < UINT16_MAX) {
        /* luma or rgb plane */
        for (i = 0; i < h; i++) {
            p = outpic->data[0] + (y+i) * outpic->linesize[0];
            for (j = 0; j < inlink->w * fade->bpp; j++) {
                /* fade->factor is using 16 lower-order bits for decimal
                 * places. 32768 = 1 << 15, it is an integer representation
                 * of 0.5 and is for rounding. */
                *p = (*p * fade->factor + 32768) >> 16;
                p++;
            }
        }

        if (outpic->data[1] && outpic->data[2]) {
            /* chroma planes */
            for (plane = 1; plane < 3; plane++) {
                for (i = 0; i < h; i++) {
                    p = outpic->data[plane] + ((y+i) >> fade->vsub) * outpic->linesize[plane];
                    for (j = 0; j < inlink->w >> fade->hsub; j++) {
                        /* 8421367 = ((128 << 1) + 1) << 15. It is an integer
                         * representation of 128.5. The .5 is for rounding
                         * purposes. */
                        *p = ((*p - 128) * fade->factor + 8421367) >> 16;
                        p++;
                    }
                }
            }
        }
    }

    avfilter_draw_slice(inlink->dst->outputs[0], y, h, slice_dir);
}

static void end_frame(AVFilterLink *inlink)
{
    FadeContext *fade = inlink->dst->priv;

    avfilter_end_frame(inlink->dst->outputs[0]);

    if (fade->frame_index >= fade->start_frame &&
        fade->frame_index <= fade->stop_frame)
        fade->factor += fade->fade_per_frame;
    fade->factor = av_clip_uint16(fade->factor);
    fade->frame_index++;
}

AVFilter avfilter_vf_fade = {
    .name          = "fade",
    .description   = NULL_IF_CONFIG_SMALL("Fade in/out input video"),
    .init          = init,
    .priv_size     = sizeof(FadeContext),
    .query_formats = query_formats,

    .inputs    = (AVFilterPad[]) {{ .name            = "default",
                                    .type            = AVMEDIA_TYPE_VIDEO,
                                    .config_props    = config_props,
                                    .get_video_buffer = avfilter_null_get_video_buffer,
                                    .start_frame      = avfilter_null_start_frame,
                                    .draw_slice      = draw_slice,
                                    .end_frame       = end_frame,
                                    .min_perms       = AV_PERM_READ | AV_PERM_WRITE,
                                    .rej_perms       = AV_PERM_PRESERVE, },
                                  { .name = NULL}},
    .outputs   = (AVFilterPad[]) {{ .name            = "default",
                                    .type            = AVMEDIA_TYPE_VIDEO, },
                                  { .name = NULL}},
};