lavfi: add fade filter

Port fade filter from libavfilter soc repo, with minor fixes by
Stefano.
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

doc/filters.texi

@@ -353,6 +353,39 @@ drawbox
 drawbox=10:20:200:60:red@@0.5"
 @end example
 
+@section fade
+
+Apply fade-in/out effect to input video.
+
+It accepts the parameters:
+@var{type}:@var{start_frame}:@var{nb_frames}
+
+@var{type} specifies if the effect type, can be either "in" for
+fade-in, or "out" for a fade-out effect.
+
+@var{start_frame} specifies the number of the start frame for starting
+to apply the fade effect.
+
+@var{nb_frames} specifies the number of frames for which the fade
+effect has to last. At the end of the fade-in effect the output video
+will have the same intensity as the input video, at the end of the
+fade-out transition the output video will be completely black.
+
+A few usage examples follow, usable too as test scenarios.
+@example
+# fade in first 30 frames of video
+fade=in:0:30
+
+# fade out last 45 frames of a 200-frame video
+fade=out:155:45
+
+# fade in first 25 frames and fade out last 25 frames of a 1000-frame video
+fade=in:0:25, fade=out:975:25
+
+# make first 5 frames black, then fade in from frame 5-24
+fade=in:5:20
+@end example
+
 @section fifo
 
 Buffer input images and send them when they are requested.

libavfilter/Makefile

@@ -27,6 +27,7 @@ OBJS-$(CONFIG_COPY_FILTER)                   += vf_copy.o
 OBJS-$(CONFIG_CROP_FILTER)                   += vf_crop.o
 OBJS-$(CONFIG_CROPDETECT_FILTER)             += vf_cropdetect.o
 OBJS-$(CONFIG_DRAWBOX_FILTER)                += vf_drawbox.o
+OBJS-$(CONFIG_FADE_FILTER)                   += vf_fade.o
 OBJS-$(CONFIG_FIFO_FILTER)                   += vf_fifo.o
 OBJS-$(CONFIG_FORMAT_FILTER)                 += vf_format.o
 OBJS-$(CONFIG_FREI0R_FILTER)                 += vf_frei0r.o

libavfilter/allfilters.c

@@ -45,6 +45,7 @@ void avfilter_register_all(void)
     REGISTER_FILTER (CROP,        crop,        vf);
     REGISTER_FILTER (CROPDETECT,  cropdetect,  vf);
     REGISTER_FILTER (DRAWBOX,     drawbox,     vf);
+    REGISTER_FILTER (FADE,        fade,        vf);
     REGISTER_FILTER (FIFO,        fifo,        vf);
     REGISTER_FILTER (FORMAT,      format,      vf);
     REGISTER_FILTER (FREI0R,      frei0r,      vf);

libavfilter/vf_fade.c

+/*
+ * Copyright (c) 2010 Brandon Mintern
+ * 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 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)
+{
+    const static 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 < 65536) {
+        /* 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[0] && outpic->data[1]) {
+            /* 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}},
+};