blend filter

Signed-off-by: Paul B Mahol <onemda@gmail.com>

4 files changed, 478 insertions, 2 deletions

diff --git a/libavfilter/Makefile b/libavfilter/Makefile
index 2449da4fcd..04ed8b8857 100644
--- a/libavfilter/Makefile
+++ b/libavfilter/Makefile
@@ -100,6 +100,7 @@ OBJS-$(CONFIG_ALPHAMERGE_FILTER)             += vf_alphamerge.o
 OBJS-$(CONFIG_BBOX_FILTER)                   += bbox.o vf_bbox.o
 OBJS-$(CONFIG_BLACKDETECT_FILTER)            += vf_blackdetect.o
 OBJS-$(CONFIG_BLACKFRAME_FILTER)             += vf_blackframe.o
+OBJS-$(CONFIG_BLEND_FILTER)                  += vf_blend.o
 OBJS-$(CONFIG_BOXBLUR_FILTER)                += vf_boxblur.o
 OBJS-$(CONFIG_COLORMATRIX_FILTER)            += vf_colormatrix.o
 OBJS-$(CONFIG_COPY_FILTER)                   += vf_copy.o
diff --git a/libavfilter/allfilters.c b/libavfilter/allfilters.c
index 61f29ffaf3..f05f8ae420 100644
--- a/libavfilter/allfilters.c
+++ b/libavfilter/allfilters.c
@@ -94,6 +94,7 @@ void avfilter_register_all(void)
     REGISTER_FILTER(BBOX,           bbox,           vf);
     REGISTER_FILTER(BLACKDETECT,    blackdetect,    vf);
     REGISTER_FILTER(BLACKFRAME,     blackframe,     vf);
+    REGISTER_FILTER(BLEND,          blend,          vf);
     REGISTER_FILTER(BOXBLUR,        boxblur,        vf);
     REGISTER_FILTER(COLORMATRIX,    colormatrix,    vf);
     REGISTER_FILTER(COPY,           copy,           vf);
diff --git a/libavfilter/version.h b/libavfilter/version.h
index ae9a7348ba..4199a2746b 100644
--- a/libavfilter/version.h
+++ b/libavfilter/version.h
@@ -29,8 +29,8 @@
 #include "libavutil/avutil.h"
 
 #define LIBAVFILTER_VERSION_MAJOR  3
-#define LIBAVFILTER_VERSION_MINOR  38
-#define LIBAVFILTER_VERSION_MICRO 106
+#define LIBAVFILTER_VERSION_MINOR  39
+#define LIBAVFILTER_VERSION_MICRO 100
 
 #define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \
                                                LIBAVFILTER_VERSION_MINOR, \
diff --git a/libavfilter/vf_blend.c b/libavfilter/vf_blend.c
new file mode 100644
index 0000000000..27d94b4e4a
--- /dev/null
+++ b/libavfilter/vf_blend.c
@@ -0,0 +1,474 @@
+/*
+ * Copyright (c) 2013 Paul B Mahol
+ *
+ * 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/imgutils.h"
+#include "libavutil/eval.h"
+#include "libavutil/opt.h"
+#include "libavutil/pixfmt.h"
+#include "avfilter.h"
+#include "bufferqueue.h"
+#include "formats.h"
+#include "internal.h"
+#include "video.h"
+
+#define TOP    0
+#define BOTTOM 1
+
+enum BlendMode {
+    BLEND_UNSET = -1,
+    BLEND_NORMAL,
+    BLEND_ADDITION,
+    BLEND_AND,
+    BLEND_AVERAGE,
+    BLEND_BURN,
+    BLEND_DARKEN,
+    BLEND_DIFFERENCE,
+    BLEND_DIVIDE,
+    BLEND_DODGE,
+    BLEND_EXCLUSION,
+    BLEND_HARDLIGHT,
+    BLEND_LIGHTEN,
+    BLEND_MULTIPLY,
+    BLEND_NEGATION,
+    BLEND_OR,
+    BLEND_OVERLAY,
+    BLEND_PHOENIX,
+    BLEND_PINLIGHT,
+    BLEND_REFLECT,
+    BLEND_SCREEN,
+    BLEND_SOFTLIGHT,
+    BLEND_SUBTRACT,
+    BLEND_VIVIDLIGHT,
+    BLEND_XOR,
+    BLEND_NB
+};
+
+static const char *const var_names[] = {   "X",   "Y",   "W",   "H",   "SW",   "SH",   "T",     "A",        "B",   "TOP",   "BOTTOM",        NULL };
+enum                                   { VAR_X, VAR_Y, VAR_W, VAR_H, VAR_SW, VAR_SH, VAR_T,   VAR_A,      VAR_B, VAR_TOP, VAR_BOTTOM, VAR_VARS_NB };
+
+typedef struct FilterParams {
+    enum BlendMode mode;
+    double values[VAR_VARS_NB];
+    double opacity;
+    AVExpr *e;
+    char *expr_str;
+    void (*blend)(const uint8_t *top, int top_linesize,
+                  const uint8_t *bottom, int bottom_linesize,
+                  uint8_t *dst, int dst_linesize,
+                  int width, int height, struct FilterParams *param);
+} FilterParams;
+
+typedef struct {
+    const AVClass *class;
+    struct FFBufQueue queue_top;
+    struct FFBufQueue queue_bottom;
+    int hsub, vsub;             ///< chroma subsampling values
+    int frame_requested;
+    char *all_expr;
+    enum BlendMode all_mode;
+    double all_opacity;
+
+    FilterParams params[4];
+} BlendContext;
+
+#define OFFSET(x) offsetof(BlendContext, x)
+#define FLAGS AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_VIDEO_PARAM
+
+static const AVOption blend_options[] = {
+    { "c0_mode", "set component #0 blend mode", OFFSET(params[0].mode), AV_OPT_TYPE_INT, {.i64=0}, 0, BLEND_NB-1, FLAGS, "mode"},
+    { "c1_mode", "set component #1 blend mode", OFFSET(params[1].mode), AV_OPT_TYPE_INT, {.i64=0}, 0, BLEND_NB-1, FLAGS, "mode"},
+    { "c2_mode", "set component #2 blend mode", OFFSET(params[2].mode), AV_OPT_TYPE_INT, {.i64=0}, 0, BLEND_NB-1, FLAGS, "mode"},
+    { "c3_mode", "set component #3 blend mode", OFFSET(params[3].mode), AV_OPT_TYPE_INT, {.i64=0}, 0, BLEND_NB-1, FLAGS, "mode"},
+    { "all_mode", "set blend mode for all components", OFFSET(all_mode), AV_OPT_TYPE_INT, {.i64=-1},-1, BLEND_NB-1, FLAGS, "mode"},
+    { "addition",   "", 0, AV_OPT_TYPE_CONST, {.i64=BLEND_ADDITION},   0, 0, FLAGS, "mode" },
+    { "and",        "", 0, AV_OPT_TYPE_CONST, {.i64=BLEND_AND},        0, 0, FLAGS, "mode" },
+    { "average",    "", 0, AV_OPT_TYPE_CONST, {.i64=BLEND_AVERAGE},    0, 0, FLAGS, "mode" },
+    { "burn",       "", 0, AV_OPT_TYPE_CONST, {.i64=BLEND_BURN},       0, 0, FLAGS, "mode" },
+    { "darken",     "", 0, AV_OPT_TYPE_CONST, {.i64=BLEND_DARKEN},     0, 0, FLAGS, "mode" },
+    { "difference", "", 0, AV_OPT_TYPE_CONST, {.i64=BLEND_DIFFERENCE}, 0, 0, FLAGS, "mode" },
+    { "divide",     "", 0, AV_OPT_TYPE_CONST, {.i64=BLEND_DIVIDE},     0, 0, FLAGS, "mode" },
+    { "dodge",      "", 0, AV_OPT_TYPE_CONST, {.i64=BLEND_DODGE},      0, 0, FLAGS, "mode" },
+    { "exclusion",  "", 0, AV_OPT_TYPE_CONST, {.i64=BLEND_EXCLUSION},  0, 0, FLAGS, "mode" },
+    { "hardlight",  "", 0, AV_OPT_TYPE_CONST, {.i64=BLEND_HARDLIGHT},  0, 0, FLAGS, "mode" },
+    { "lighten",    "", 0, AV_OPT_TYPE_CONST, {.i64=BLEND_LIGHTEN},    0, 0, FLAGS, "mode" },
+    { "multiply",   "", 0, AV_OPT_TYPE_CONST, {.i64=BLEND_MULTIPLY},   0, 0, FLAGS, "mode" },
+    { "negation",   "", 0, AV_OPT_TYPE_CONST, {.i64=BLEND_NEGATION},   0, 0, FLAGS, "mode" },
+    { "normal",     "", 0, AV_OPT_TYPE_CONST, {.i64=BLEND_NORMAL},     0, 0, FLAGS, "mode" },
+    { "or",         "", 0, AV_OPT_TYPE_CONST, {.i64=BLEND_OR},         0, 0, FLAGS, "mode" },
+    { "overlay",    "", 0, AV_OPT_TYPE_CONST, {.i64=BLEND_OVERLAY},    0, 0, FLAGS, "mode" },
+    { "phoenix",    "", 0, AV_OPT_TYPE_CONST, {.i64=BLEND_PHOENIX},    0, 0, FLAGS, "mode" },
+    { "pinlight",   "", 0, AV_OPT_TYPE_CONST, {.i64=BLEND_PINLIGHT},   0, 0, FLAGS, "mode" },
+    { "reflect",    "", 0, AV_OPT_TYPE_CONST, {.i64=BLEND_REFLECT},    0, 0, FLAGS, "mode" },
+    { "screen",     "", 0, AV_OPT_TYPE_CONST, {.i64=BLEND_SCREEN},     0, 0, FLAGS, "mode" },
+    { "softlight",  "", 0, AV_OPT_TYPE_CONST, {.i64=BLEND_SOFTLIGHT},  0, 0, FLAGS, "mode" },
+    { "subtract",   "", 0, AV_OPT_TYPE_CONST, {.i64=BLEND_SUBTRACT},   0, 0, FLAGS, "mode" },
+    { "vividlight", "", 0, AV_OPT_TYPE_CONST, {.i64=BLEND_VIVIDLIGHT}, 0, 0, FLAGS, "mode" },
+    { "xor",        "", 0, AV_OPT_TYPE_CONST, {.i64=BLEND_XOR},        0, 0, FLAGS, "mode" },
+    { "c0_expr",  "set color component #0 expression", OFFSET(params[0].expr_str), AV_OPT_TYPE_STRING, {.str=NULL}, CHAR_MIN, CHAR_MAX, FLAGS },
+    { "c1_expr",  "set color component #1 expression", OFFSET(params[1].expr_str), AV_OPT_TYPE_STRING, {.str=NULL}, CHAR_MIN, CHAR_MAX, FLAGS },
+    { "c2_expr",  "set color component #2 expression", OFFSET(params[2].expr_str), AV_OPT_TYPE_STRING, {.str=NULL}, CHAR_MIN, CHAR_MAX, FLAGS },
+    { "c3_expr",  "set color component #3 expression", OFFSET(params[3].expr_str), AV_OPT_TYPE_STRING, {.str=NULL}, CHAR_MIN, CHAR_MAX, FLAGS },
+    { "all_expr", "set expression for all color components", OFFSET(all_expr), AV_OPT_TYPE_STRING, {.str=NULL}, CHAR_MIN, CHAR_MAX, FLAGS },
+    { "c0_opacity",  "set color component #0 opacity", OFFSET(params[0].opacity), AV_OPT_TYPE_DOUBLE, {.dbl=1}, 0, 1, FLAGS },
+    { "c1_opacity",  "set color component #1 opacity", OFFSET(params[1].opacity), AV_OPT_TYPE_DOUBLE, {.dbl=1}, 0, 1, FLAGS },
+    { "c2_opacity",  "set color component #2 opacity", OFFSET(params[2].opacity), AV_OPT_TYPE_DOUBLE, {.dbl=1}, 0, 1, FLAGS },
+    { "c3_opacity",  "set color component #3 opacity", OFFSET(params[3].opacity), AV_OPT_TYPE_DOUBLE, {.dbl=1}, 0, 1, FLAGS },
+    { "all_opacity", "set opacity for all color components", OFFSET(all_opacity), AV_OPT_TYPE_DOUBLE, {.dbl=1}, 0, 1, FLAGS},
+    { NULL },
+};
+
+AVFILTER_DEFINE_CLASS(blend);
+
+static void blend_normal(const uint8_t *top, int top_linesize,
+                         const uint8_t *bottom, int bottom_linesize,
+                         uint8_t *dst, int dst_linesize,
+                         int width, int height, FilterParams *param)
+{
+    av_image_copy_plane(dst, dst_linesize, top, top_linesize, width, height);
+}
+
+#define DEFINE_BLEND(name, expr)                                      \
+static void blend_## name(const uint8_t *top, int top_linesize,       \
+                          const uint8_t *bottom, int bottom_linesize, \
+                          uint8_t *dst, int dst_linesize,             \
+                          int width, int height, FilterParams *param) \
+{                                                                     \
+    double opacity = param->opacity;                                  \
+    int i, j;                                                         \
+                                                                      \
+    for (i = 0; i < height; i++) {                                    \
+        for (j = 0; j < width; j++) {                                 \
+            dst[j] = top[j] + ((expr) - top[j]) * opacity;            \
+        }                                                             \
+        dst    += dst_linesize;                                       \
+        top    += top_linesize;                                       \
+        bottom += bottom_linesize;                                    \
+    }                                                                 \
+}
+
+#define A top[j]
+#define B bottom[j]
+
+#define MULTIPLY(x, a, b) (x * ((a * b) / 255))
+#define SCREEN(x, a, b)   (255 - x * ((255 - a) * (255 - b) / 255))
+#define BURN(a, b)        ((a == 0) ? a : FFMAX(0, 255 - ((255 - b) << 8) / a))
+#define DODGE(a, b)       ((a == 255) ? a : FFMIN(255, ((b << 8) / (255 - a))))
+
+DEFINE_BLEND(addition,   FFMIN(255, A + B))
+DEFINE_BLEND(average,    (A + B) / 2)
+DEFINE_BLEND(subtract,   FFMAX(0, A - B))
+DEFINE_BLEND(multiply,   MULTIPLY(1, A, B))
+DEFINE_BLEND(negation,   255 - FFABS(255 - A - B))
+DEFINE_BLEND(difference, FFABS(A - B))
+DEFINE_BLEND(screen,     SCREEN(1, A, B))
+DEFINE_BLEND(overlay,    (A < 128) ? MULTIPLY(2, A, B) : SCREEN(2, A, B))
+DEFINE_BLEND(hardlight,  (B < 128) ? MULTIPLY(2, B, A) : SCREEN(2, B, A))
+DEFINE_BLEND(darken,     FFMIN(A, B))
+DEFINE_BLEND(lighten,    FFMAX(A, B))
+DEFINE_BLEND(divide,     ((float)A / ((float)B) * 255))
+DEFINE_BLEND(dodge,      DODGE(A, B))
+DEFINE_BLEND(burn,       BURN(A, B))
+DEFINE_BLEND(softlight,  (A > 127) ? B + (255 - B) * (A - 127.5) / 127.5 * (0.5 - FFABS(B - 127.5) / 255): B - B * ((127.5 - A) / 127.5) * (0.5 - FFABS(B - 127.5)/255))
+DEFINE_BLEND(exclusion,  A + B - 2 * A * B / 255)
+DEFINE_BLEND(pinlight,   (B < 128) ? FFMIN(A, 2 * B) : FFMAX(A, 2 * (B - 128)))
+DEFINE_BLEND(phoenix,    FFMIN(A, B) - FFMAX(A, B) + 255)
+DEFINE_BLEND(reflect,    (B == 255) ? B : FFMIN(255, (A * A / (255 - B))))
+DEFINE_BLEND(and,        A & B)
+DEFINE_BLEND(or,         A | B)
+DEFINE_BLEND(xor,        A ^ B)
+DEFINE_BLEND(vividlight, (B < 128) ? BURN(A, 2 * B) : DODGE(A, 2 * (B - 128)))
+
+static void blend_expr(const uint8_t *top, int top_linesize,
+                       const uint8_t *bottom, int bottom_linesize,
+                       uint8_t *dst, int dst_linesize,
+                       int width, int height,
+                       FilterParams *param)
+{
+    AVExpr *e = param->e;
+    double *values = param->values;
+    int y, x;
+
+    for (y = 0; y < height; y++) {
+        values[VAR_Y] = y;
+        for (x = 0; x < width; x++) {
+            values[VAR_X]      = x;
+            values[VAR_TOP]    = values[VAR_A] = top[x];
+            values[VAR_BOTTOM] = values[VAR_B] = bottom[x];
+            dst[x] = av_expr_eval(e, values, NULL);
+        }
+        dst    += dst_linesize;
+        top    += top_linesize;
+        bottom += bottom_linesize;
+    }
+}
+
+static av_cold int init(AVFilterContext *ctx, const char *args)
+{
+    BlendContext *b = ctx->priv;
+    int ret, plane;
+
+    b->class = &blend_class;
+    av_opt_set_defaults(b);
+
+    if ((ret = av_set_options_string(b, args, "=", ":")) < 0)
+        return ret;
+
+    for (plane = 0; plane < FF_ARRAY_ELEMS(b->params); plane++) {
+        FilterParams *param = &b->params[plane];
+
+        if (b->all_mode >= 0)
+            param->mode = b->all_mode;
+        if (b->all_opacity < 1)
+            param->opacity = b->all_opacity;
+
+        switch (param->mode) {
+        case BLEND_ADDITION:   param->blend = blend_addition;   break;
+        case BLEND_AND:        param->blend = blend_and;        break;
+        case BLEND_AVERAGE:    param->blend = blend_average;    break;
+        case BLEND_BURN:       param->blend = blend_burn;       break;
+        case BLEND_DARKEN:     param->blend = blend_darken;     break;
+        case BLEND_DIFFERENCE: param->blend = blend_difference; break;
+        case BLEND_DIVIDE:     param->blend = blend_divide;     break;
+        case BLEND_DODGE:      param->blend = blend_dodge;      break;
+        case BLEND_EXCLUSION:  param->blend = blend_exclusion;  break;
+        case BLEND_HARDLIGHT:  param->blend = blend_hardlight;  break;
+        case BLEND_LIGHTEN:    param->blend = blend_lighten;    break;
+        case BLEND_MULTIPLY:   param->blend = blend_multiply;   break;
+        case BLEND_NEGATION:   param->blend = blend_negation;   break;
+        case BLEND_NORMAL:     param->blend = blend_normal;     break;
+        case BLEND_OR:         param->blend = blend_or;         break;
+        case BLEND_OVERLAY:    param->blend = blend_overlay;    break;
+        case BLEND_PHOENIX:    param->blend = blend_phoenix;    break;
+        case BLEND_PINLIGHT:   param->blend = blend_pinlight;   break;
+        case BLEND_REFLECT:    param->blend = blend_reflect;    break;
+        case BLEND_SCREEN:     param->blend = blend_screen;     break;
+        case BLEND_SOFTLIGHT:  param->blend = blend_softlight;  break;
+        case BLEND_SUBTRACT:   param->blend = blend_subtract;   break;
+        case BLEND_VIVIDLIGHT: param->blend = blend_vividlight; break;
+        case BLEND_XOR:        param->blend = blend_xor;        break;
+        }
+
+        if (b->all_expr && !param->expr_str) {
+            param->expr_str = av_strdup(b->all_expr);
+            if (!param->expr_str)
+                return AVERROR(ENOMEM);
+        }
+        if (param->expr_str) {
+            ret = av_expr_parse(&param->e, param->expr_str, var_names,
+                                NULL, NULL, NULL, NULL, 0, ctx);
+            if (ret < 0)
+                return ret;
+            param->blend = blend_expr;
+        }
+    }
+
+    return 0;
+}
+
+static int query_formats(AVFilterContext *ctx)
+{
+    static const enum AVPixelFormat pix_fmts[] = {
+        AV_PIX_FMT_YUVA444P, AV_PIX_FMT_YUVA422P, AV_PIX_FMT_YUVA420P,
+        AV_PIX_FMT_YUV444P, AV_PIX_FMT_YUV422P, AV_PIX_FMT_YUV420P,
+        AV_PIX_FMT_GBRP, AV_PIX_FMT_GRAY8, AV_PIX_FMT_NONE
+    };
+
+    ff_set_common_formats(ctx, ff_make_format_list(pix_fmts));
+    return 0;
+}
+
+static int config_output(AVFilterLink *outlink)
+{
+    AVFilterContext *ctx = outlink->src;
+    AVFilterLink *toplink = ctx->inputs[TOP];
+    AVFilterLink *bottomlink = ctx->inputs[BOTTOM];
+
+    if (toplink->format != bottomlink->format) {
+        av_log(ctx, AV_LOG_ERROR, "inputs must be of same pixel format\n");
+        return AVERROR(EINVAL);
+    }
+    if (toplink->w                        != bottomlink->w ||
+        toplink->h                        != bottomlink->h ||
+        toplink->sample_aspect_ratio.num != bottomlink->sample_aspect_ratio.num ||
+        toplink->sample_aspect_ratio.den != bottomlink->sample_aspect_ratio.den) {
+        av_log(ctx, AV_LOG_ERROR, "First input link %s parameters "
+               "(size %dx%d, SAR %d:%d) do not match the corresponding "
+               "second input link %s parameters (%dx%d, SAR %d:%d)\n",
+               ctx->input_pads[TOP].name, toplink->w, toplink->h,
+               toplink->sample_aspect_ratio.num,
+               toplink->sample_aspect_ratio.den,
+               ctx->input_pads[BOTTOM].name, bottomlink->w, bottomlink->h,
+               bottomlink->sample_aspect_ratio.num,
+               bottomlink->sample_aspect_ratio.den);
+        return AVERROR(EINVAL);
+    }
+
+    outlink->w = toplink->w;
+    outlink->h = bottomlink->h;
+    outlink->time_base = toplink->time_base;
+    outlink->sample_aspect_ratio = toplink->sample_aspect_ratio;
+    outlink->frame_rate = toplink->frame_rate;
+    return 0;
+}
+
+static int config_input_top(AVFilterLink *inlink)
+{
+    BlendContext *b = inlink->dst->priv;
+    const AVPixFmtDescriptor *pix_desc = av_pix_fmt_desc_get(inlink->format);
+
+    b->hsub = pix_desc->log2_chroma_w;
+    b->vsub = pix_desc->log2_chroma_h;
+    return 0;
+}
+
+static av_cold void uninit(AVFilterContext *ctx)
+{
+    BlendContext *b = ctx->priv;
+    int i;
+
+    av_opt_free(b);
+    ff_bufqueue_discard_all(&b->queue_top);
+    ff_bufqueue_discard_all(&b->queue_bottom);
+
+    for (i = 0; i < FF_ARRAY_ELEMS(b->params); i++)
+        av_expr_free(b->params[i].e);
+}
+
+static int request_frame(AVFilterLink *outlink)
+{
+    AVFilterContext *ctx = outlink->src;
+    BlendContext *b = ctx->priv;
+    int in, ret;
+
+    b->frame_requested = 1;
+    while (b->frame_requested) {
+        in = ff_bufqueue_peek(&b->queue_top, TOP) ? BOTTOM : TOP;
+        ret = ff_request_frame(ctx->inputs[in]);
+        if (ret < 0)
+            return ret;
+    }
+    return 0;
+}
+
+static void blend_frame(AVFilterContext *ctx,
+                        AVFilterBufferRef *top_buf,
+                        AVFilterBufferRef *bottom_buf,
+                        AVFilterBufferRef *dst_buf)
+{
+    BlendContext *b = ctx->priv;
+    AVFilterLink *inlink = ctx->inputs[0];
+    FilterParams *param;
+    int plane;
+
+    for (plane = 0; dst_buf->data[plane]; plane++) {
+        int hsub = plane == 1 || plane == 2 ? b->hsub : 0;
+        int vsub = plane == 1 || plane == 2 ? b->vsub : 0;
+        int outw = dst_buf->video->w >> hsub;
+        int outh = dst_buf->video->h >> vsub;
+        uint8_t *dst    = dst_buf->data[plane];
+        uint8_t *top    = top_buf->data[plane];
+        uint8_t *bottom = bottom_buf->data[plane];
+
+        param = &b->params[plane];
+        param->values[VAR_T]  = dst_buf->pts == AV_NOPTS_VALUE ? NAN : dst_buf->pts * av_q2d(inlink->time_base);
+        param->values[VAR_W]  = outw;
+        param->values[VAR_H]  = outh;
+        param->values[VAR_SW] = outw / dst_buf->video->w;
+        param->values[VAR_SH] = outh / dst_buf->video->h;
+        param->blend(top, top_buf->linesize[plane],
+                     bottom, bottom_buf->linesize[plane],
+                     dst, dst_buf->linesize[plane], outw, outh, param);
+    }
+}
+
+static int filter_frame(AVFilterLink *inlink, AVFilterBufferRef *buf)
+{
+    AVFilterContext *ctx = inlink->dst;
+    AVFilterLink *outlink = ctx->outputs[0];
+    BlendContext *b = ctx->priv;
+
+    int ret = 0;
+    int is_bottom = (inlink == ctx->inputs[BOTTOM]);
+    struct FFBufQueue *queue =
+        (is_bottom ? &b->queue_bottom : &b->queue_top);
+    ff_bufqueue_add(ctx, queue, buf);
+
+    while (1) {
+        AVFilterBufferRef *top_buf, *bottom_buf, *out_buf;
+
+        if (!ff_bufqueue_peek(&b->queue_top, TOP) ||
+            !ff_bufqueue_peek(&b->queue_bottom, BOTTOM)) break;
+
+        top_buf = ff_bufqueue_get(&b->queue_top);
+        bottom_buf = ff_bufqueue_get(&b->queue_bottom);
+
+        out_buf = ff_get_video_buffer(outlink, AV_PERM_WRITE,
+                                      outlink->w, outlink->h);
+        if (!out_buf) {
+            return AVERROR(ENOMEM);
+        }
+        avfilter_copy_buffer_ref_props(out_buf, top_buf);
+
+        b->frame_requested = 0;
+        blend_frame(ctx, top_buf, bottom_buf, out_buf);
+        ret = ff_filter_frame(ctx->outputs[0], out_buf);
+        avfilter_unref_buffer(top_buf);
+        avfilter_unref_buffer(bottom_buf);
+    }
+    return ret;
+}
+
+static const AVFilterPad blend_inputs[] = {
+    {
+        .name             = "top",
+        .type             = AVMEDIA_TYPE_VIDEO,
+        .config_props     = config_input_top,
+        .filter_frame     = filter_frame,
+        .min_perms        = AV_PERM_READ | AV_PERM_PRESERVE,
+    },{
+        .name             = "bottom",
+        .type             = AVMEDIA_TYPE_VIDEO,
+        .filter_frame     = filter_frame,
+        .min_perms        = AV_PERM_READ | AV_PERM_PRESERVE,
+    },
+    { NULL }
+};
+
+static const AVFilterPad blend_outputs[] = {
+    {
+        .name          = "default",
+        .type          = AVMEDIA_TYPE_VIDEO,
+        .config_props  = config_output,
+        .request_frame = request_frame,
+    },
+    { NULL }
+};
+
+AVFilter avfilter_vf_blend = {
+    .name          = "blend",
+    .description   = NULL_IF_CONFIG_SMALL("Blend two video frames into each other."),
+    .init          = init,
+    .uninit        = uninit,
+    .priv_size     = sizeof(BlendContext),
+    .query_formats = query_formats,
+    .inputs        = blend_inputs,
+    .outputs       = blend_outputs,
+    .priv_class    = &blend_class,
+};