/*
  * Copyright (c) 2010 Stefano Sabatini
  * Copyright (c) 2010 Baptiste Coudurier
  * 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
  * overlay one video on top of another
  */
 

 /* #define DEBUG */
 

 #include "avfilter.h"

 #include "formats.h"

 #include "libavutil/common.h"

 #include "libavutil/eval.h"
 #include "libavutil/avstring.h"

 #include "libavutil/opt.h"

 #include "libavutil/pixdesc.h"

 #include "libavutil/imgutils.h"

 #include "libavutil/mathematics.h"

 #include "libavutil/timestamp.h"

 #include "internal.h"

 #include "bufferqueue.h"

 #include "drawutils.h"

 #include "video.h"

 static const char *const var_names[] = {

     "main_w",    "W", ///< width  of the main    video
     "main_h",    "H", ///< height of the main    video
     "overlay_w", "w", ///< width  of the overlay video
     "overlay_h", "h", ///< height of the overlay video
     NULL
 };
 
 enum var_name {
     VAR_MAIN_W,    VAR_MW,
     VAR_MAIN_H,    VAR_MH,
     VAR_OVERLAY_W, VAR_OW,
     VAR_OVERLAY_H, VAR_OH,
     VAR_VARS_NB
 };
 
 #define MAIN    0
 #define OVERLAY 1
 

 #define R 0
 #define G 1
 #define B 2
 #define A 3
 
 #define Y 0
 #define U 1
 #define V 2
 

 typedef struct {

     const AVClass *class;

     int x, y;                   ///< position of overlayed picture
 

     int allow_packed_rgb;

     uint8_t frame_requested;
     uint8_t overlay_eof;

     uint8_t main_is_packed_rgb;
     uint8_t main_rgba_map[4];
     uint8_t main_has_alpha;
     uint8_t overlay_is_packed_rgb;
     uint8_t overlay_rgba_map[4];
     uint8_t overlay_has_alpha;
 

     AVFilterBufferRef *overpicref;
     struct FFBufQueue queue_main;
     struct FFBufQueue queue_over;

     int main_pix_step[4];       ///< steps per pixel for each plane of the main output
     int overlay_pix_step[4];    ///< steps per pixel for each plane of the overlay

     int hsub, vsub;             ///< chroma subsampling values
 

     char *x_expr, *y_expr;

 } OverlayContext;
 

 #define OFFSET(x) offsetof(OverlayContext, x)

 #define FLAGS AV_OPT_FLAG_VIDEO_PARAM|AV_OPT_FLAG_FILTERING_PARAM

 static const AVOption overlay_options[] = {

     { "x", "set the x expression", OFFSET(x_expr), AV_OPT_TYPE_STRING, {.str = "0"}, CHAR_MIN, CHAR_MAX, FLAGS },
     { "y", "set the y expression", OFFSET(y_expr), AV_OPT_TYPE_STRING, {.str = "0"}, CHAR_MIN, CHAR_MAX, FLAGS },

     {"rgb", "force packed RGB in input and output", OFFSET(allow_packed_rgb), AV_OPT_TYPE_INT, {.i64=0}, 0, 1, FLAGS },

     {NULL},
 };
 

 AVFILTER_DEFINE_CLASS(overlay);

 static av_cold int init(AVFilterContext *ctx, const char *args)

 {
     OverlayContext *over = ctx->priv;
     char *args1 = av_strdup(args);
     char *expr, *bufptr = NULL;
     int ret = 0;
 
     over->class = &overlay_class;
     av_opt_set_defaults(over);
 
     if (expr = av_strtok(args1, ":", &bufptr)) {

         av_free(over->x_expr);

         if (!(over->x_expr = av_strdup(expr))) {
             ret = AVERROR(ENOMEM);
             goto end;
         }
     }
     if (expr = av_strtok(NULL, ":", &bufptr)) {

         av_free(over->y_expr);

         if (!(over->y_expr = av_strdup(expr))) {
             ret = AVERROR(ENOMEM);
             goto end;
         }
     }
 
     if (bufptr && (ret = av_set_options_string(over, bufptr, "=", ":")) < 0)
         goto end;
 
 end:
     av_free(args1);
     return ret;

 }
 
 static av_cold void uninit(AVFilterContext *ctx)
 {
     OverlayContext *over = ctx->priv;
 

     av_freep(&over->x_expr);
     av_freep(&over->y_expr);
 

     avfilter_unref_bufferp(&over->overpicref);

     ff_bufqueue_discard_all(&over->queue_main);
     ff_bufqueue_discard_all(&over->queue_over);

 }
 
 static int query_formats(AVFilterContext *ctx)
 {

     OverlayContext *over = ctx->priv;
 
     /* overlay formats contains alpha, for avoiding conversion with alpha information loss */
     const enum PixelFormat main_pix_fmts_yuv[] = { PIX_FMT_YUV420P,  PIX_FMT_NONE };
     const enum PixelFormat overlay_pix_fmts_yuv[] = { PIX_FMT_YUVA420P, PIX_FMT_NONE };
     const enum PixelFormat main_pix_fmts_rgb[] = {
         PIX_FMT_ARGB,  PIX_FMT_RGBA,
         PIX_FMT_ABGR,  PIX_FMT_BGRA,
         PIX_FMT_RGB24, PIX_FMT_BGR24,
         PIX_FMT_NONE
     };
     const enum PixelFormat overlay_pix_fmts_rgb[] = {
         PIX_FMT_ARGB,  PIX_FMT_RGBA,
         PIX_FMT_ABGR,  PIX_FMT_BGRA,
         PIX_FMT_NONE
     };
 
     AVFilterFormats *main_formats;
     AVFilterFormats *overlay_formats;
 
     if (over->allow_packed_rgb) {

         main_formats    = ff_make_format_list(main_pix_fmts_rgb);
         overlay_formats = ff_make_format_list(overlay_pix_fmts_rgb);

     } else {

         main_formats    = ff_make_format_list(main_pix_fmts_yuv);
         overlay_formats = ff_make_format_list(overlay_pix_fmts_yuv);

     }

     ff_formats_ref(main_formats,    &ctx->inputs [MAIN   ]->out_formats);
     ff_formats_ref(overlay_formats, &ctx->inputs [OVERLAY]->out_formats);
     ff_formats_ref(main_formats,    &ctx->outputs[MAIN   ]->in_formats );

 
     return 0;
 }
 

 static const enum PixelFormat alpha_pix_fmts[] = {

     PIX_FMT_YUVA420P, PIX_FMT_ARGB, PIX_FMT_ABGR, PIX_FMT_RGBA,
     PIX_FMT_BGRA, PIX_FMT_NONE
 };
 

 static int config_input_main(AVFilterLink *inlink)
 {
     OverlayContext *over = inlink->dst->priv;
     const AVPixFmtDescriptor *pix_desc = &av_pix_fmt_descriptors[inlink->format];
 

     av_image_fill_max_pixsteps(over->main_pix_step,    NULL, pix_desc);
 

     over->hsub = pix_desc->log2_chroma_w;
     over->vsub = pix_desc->log2_chroma_h;
 

     over->main_is_packed_rgb =
         ff_fill_rgba_map(over->main_rgba_map, inlink->format) >= 0;
     over->main_has_alpha = ff_fmt_is_in(inlink->format, alpha_pix_fmts);

     return 0;
 }
 
 static int config_input_overlay(AVFilterLink *inlink)
 {
     AVFilterContext *ctx  = inlink->dst;
     OverlayContext  *over = inlink->dst->priv;
     char *expr;
     double var_values[VAR_VARS_NB], res;
     int ret;

     const AVPixFmtDescriptor *pix_desc = &av_pix_fmt_descriptors[inlink->format];
 
     av_image_fill_max_pixsteps(over->overlay_pix_step, NULL, pix_desc);

 
     /* Finish the configuration by evaluating the expressions
        now when both inputs are configured. */
     var_values[VAR_MAIN_W   ] = var_values[VAR_MW] = ctx->inputs[MAIN   ]->w;
     var_values[VAR_MAIN_H   ] = var_values[VAR_MH] = ctx->inputs[MAIN   ]->h;
     var_values[VAR_OVERLAY_W] = var_values[VAR_OW] = ctx->inputs[OVERLAY]->w;
     var_values[VAR_OVERLAY_H] = var_values[VAR_OH] = ctx->inputs[OVERLAY]->h;
 
     if ((ret = av_expr_parse_and_eval(&res, (expr = over->x_expr), var_names, var_values,
                                       NULL, NULL, NULL, NULL, NULL, 0, ctx)) < 0)
         goto fail;
     over->x = res;
     if ((ret = av_expr_parse_and_eval(&res, (expr = over->y_expr), var_names, var_values,
                                       NULL, NULL, NULL, NULL, NULL, 0, ctx)))
         goto fail;
     over->y = res;
     /* x may depend on y */
     if ((ret = av_expr_parse_and_eval(&res, (expr = over->x_expr), var_names, var_values,
                                       NULL, NULL, NULL, NULL, NULL, 0, ctx)) < 0)
         goto fail;
     over->x = res;
 

     over->overlay_is_packed_rgb =
         ff_fill_rgba_map(over->overlay_rgba_map, inlink->format) >= 0;
     over->overlay_has_alpha = ff_fmt_is_in(inlink->format, alpha_pix_fmts);
 

     av_log(ctx, AV_LOG_VERBOSE,

            "main w:%d h:%d fmt:%s overlay x:%d y:%d w:%d h:%d fmt:%s\n",
            ctx->inputs[MAIN]->w, ctx->inputs[MAIN]->h,
            av_pix_fmt_descriptors[ctx->inputs[MAIN]->format].name,
            over->x, over->y,
            ctx->inputs[OVERLAY]->w, ctx->inputs[OVERLAY]->h,
            av_pix_fmt_descriptors[ctx->inputs[OVERLAY]->format].name);
 
     if (over->x < 0 || over->y < 0 ||
         over->x + var_values[VAR_OVERLAY_W] > var_values[VAR_MAIN_W] ||
         over->y + var_values[VAR_OVERLAY_H] > var_values[VAR_MAIN_H]) {
         av_log(ctx, AV_LOG_ERROR,
                "Overlay area (%d,%d)<->(%d,%d) not within the main area (0,0)<->(%d,%d) or zero-sized\n",
                over->x, over->y,
                (int)(over->x + var_values[VAR_OVERLAY_W]),
                (int)(over->y + var_values[VAR_OVERLAY_H]),
                (int)var_values[VAR_MAIN_W], (int)var_values[VAR_MAIN_H]);
         return AVERROR(EINVAL);
     }
     return 0;
 
 fail:
     av_log(NULL, AV_LOG_ERROR,
            "Error when evaluating the expression '%s'\n", expr);
     return ret;
 }
 
 static int config_output(AVFilterLink *outlink)
 {
     AVFilterContext *ctx = outlink->src;
     int exact;
     // common timebase computation:
     AVRational tb1 = ctx->inputs[MAIN   ]->time_base;
     AVRational tb2 = ctx->inputs[OVERLAY]->time_base;
     AVRational *tb = &ctx->outputs[0]->time_base;
     exact = av_reduce(&tb->num, &tb->den,
                       av_gcd((int64_t)tb1.num * tb2.den,
                              (int64_t)tb2.num * tb1.den),
                       (int64_t)tb1.den * tb2.den, INT_MAX);

     av_log(ctx, AV_LOG_VERBOSE,

            "main_tb:%d/%d overlay_tb:%d/%d -> tb:%d/%d exact:%d\n",
            tb1.num, tb1.den, tb2.num, tb2.den, tb->num, tb->den, exact);
     if (!exact)
         av_log(ctx, AV_LOG_WARNING,
                "Timestamp conversion inexact, timestamp information loss may occurr\n");
 
     outlink->w = ctx->inputs[MAIN]->w;
     outlink->h = ctx->inputs[MAIN]->h;
 
     return 0;
 }
 
 static AVFilterBufferRef *get_video_buffer(AVFilterLink *link, int perms, int w, int h)
 {

     return ff_get_video_buffer(link->dst->outputs[0], perms, w, h);

 }
 

 // divide by 255 and round to nearest
 // apply a fast variant: (X+127)/255 = ((X+127)*257+257)>>16 = ((X+128)*257)>>16
 #define FAST_DIV255(x) ((((x) + 128) * 257) >> 16)
 

 static void blend_slice(AVFilterContext *ctx,
                         AVFilterBufferRef *dst, AVFilterBufferRef *src,
                         int x, int y, int w, int h,
                         int slice_y, int slice_w, int slice_h)
 {
     OverlayContext *over = ctx->priv;
     int i, j, k;
     int width, height;
     int overlay_end_y = y+h;
     int slice_end_y = slice_y+slice_h;
     int end_y, start_y;
 
     width = FFMIN(slice_w - x, w);
     end_y = FFMIN(slice_end_y, overlay_end_y);
     start_y = FFMAX(y, slice_y);
     height = end_y - start_y;
 

     if (over->main_is_packed_rgb) {
         uint8_t *dp = dst->data[0] + x * over->main_pix_step[0] +
                       start_y * dst->linesize[0];

         uint8_t *sp = src->data[0];

         uint8_t alpha;          ///< the amount of overlay to blend on to main
         const int dr = over->main_rgba_map[R];
         const int dg = over->main_rgba_map[G];
         const int db = over->main_rgba_map[B];

         const int da = over->main_rgba_map[A];

         const int dstep = over->main_pix_step[0];
         const int sr = over->overlay_rgba_map[R];
         const int sg = over->overlay_rgba_map[G];
         const int sb = over->overlay_rgba_map[B];
         const int sa = over->overlay_rgba_map[A];
         const int sstep = over->overlay_pix_step[0];

         const int main_has_alpha = over->main_has_alpha;

         if (slice_y > y)
             sp += (slice_y - y) * src->linesize[0];
         for (i = 0; i < height; i++) {
             uint8_t *d = dp, *s = sp;
             for (j = 0; j < width; j++) {

                 alpha = s[sa];

 
                 // if the main channel has an alpha channel, alpha has to be calculated
                 // to create an un-premultiplied (straight) alpha value
                 if (main_has_alpha && alpha != 0 && alpha != 255) {
                     // apply the general equation:
                     // alpha = alpha_overlay / ( (alpha_main + alpha_overlay) - (alpha_main * alpha_overlay) )
                     alpha =
                         // the next line is a faster version of: 255 * 255 * alpha
                         ( (alpha << 16) - (alpha << 9) + alpha )
                         /
                         // the next line is a faster version of: 255 * (alpha + d[da])
                         ( ((alpha + d[da]) << 8 ) - (alpha + d[da])
                           - d[da] * alpha );
                 }
 

                 switch (alpha) {
                 case 0:
                     break;
                 case 255:
                     d[dr] = s[sr];
                     d[dg] = s[sg];
                     d[db] = s[sb];
                     break;
                 default:
                     // main_value = main_value * (1 - alpha) + overlay_value * alpha
                     // since alpha is in the range 0-255, the result must divided by 255
                     d[dr] = FAST_DIV255(d[dr] * (255 - alpha) + s[sr] * alpha);
                     d[dg] = FAST_DIV255(d[dg] * (255 - alpha) + s[sg] * alpha);
                     d[db] = FAST_DIV255(d[db] * (255 - alpha) + s[sb] * alpha);
                 }

                 if (main_has_alpha) {
                     switch (alpha) {
                     case 0:
                         break;
                     case 255:
                         d[da] = s[sa];
                         break;
                     default:
                         // apply alpha compositing: main_alpha += (1-main_alpha) * overlay_alpha
                         d[da] += FAST_DIV255((255 - d[da]) * s[sa]);
                     }
                 }

                 d += dstep;
                 s += sstep;

             }
             dp += dst->linesize[0];
             sp += src->linesize[0];
         }
     } else {
         for (i = 0; i < 3; i++) {
             int hsub = i ? over->hsub : 0;
             int vsub = i ? over->vsub : 0;
             uint8_t *dp = dst->data[i] + (x >> hsub) +
                 (start_y >> vsub) * dst->linesize[i];
             uint8_t *sp = src->data[i];
             uint8_t *ap = src->data[3];
             int wp = FFALIGN(width, 1<<hsub) >> hsub;
             int hp = FFALIGN(height, 1<<vsub) >> vsub;
             if (slice_y > y) {
                 sp += ((slice_y - y) >> vsub) * src->linesize[i];
                 ap += (slice_y - y) * src->linesize[3];
             }
             for (j = 0; j < hp; j++) {
                 uint8_t *d = dp, *s = sp, *a = ap;
                 for (k = 0; k < wp; k++) {
                     // average alpha for color components, improve quality
                     int alpha_v, alpha_h, alpha;
                     if (hsub && vsub && j+1 < hp && k+1 < wp) {
                         alpha = (a[0] + a[src->linesize[3]] +
                                  a[1] + a[src->linesize[3]+1]) >> 2;
                     } else if (hsub || vsub) {
                         alpha_h = hsub && k+1 < wp ?
                             (a[0] + a[1]) >> 1 : a[0];
                         alpha_v = vsub && j+1 < hp ?
                             (a[0] + a[src->linesize[3]]) >> 1 : a[0];
                         alpha = (alpha_v + alpha_h) >> 1;
                     } else
                         alpha = a[0];

                     *d = FAST_DIV255(*d * (255 - alpha) + *s * alpha);
                     s++;

                     d++;
                     a += 1 << hsub;
                 }
                 dp += dst->linesize[i];
                 sp += src->linesize[i];
                 ap += (1 << vsub) * src->linesize[3];
             }
         }
     }
 }
 

 static int try_start_frame(AVFilterContext *ctx, AVFilterBufferRef *mainpic)

 {

     OverlayContext *over = ctx->priv;
     AVFilterLink *outlink = ctx->outputs[0];
     AVFilterBufferRef *next_overpic, *outpicref;

     int ret;

 
     /* Discard obsolete overlay frames: if there is a next frame with pts is
      * before the main frame, we can drop the current overlay. */
     while (1) {
         next_overpic = ff_bufqueue_peek(&over->queue_over, 0);
         if (!next_overpic || next_overpic->pts > mainpic->pts)
             break;
         ff_bufqueue_get(&over->queue_over);
         avfilter_unref_buffer(over->overpicref);
         over->overpicref = next_overpic;
     }
     /* If there is no next frame and no EOF and the overlay frame is before
      * the main frame, we can not know yet if it will be superseded. */
     if (!over->queue_over.available && !over->overlay_eof &&
         (!over->overpicref || over->overpicref->pts < mainpic->pts))
         return AVERROR(EAGAIN);
     /* At this point, we know that the current overlay frame extends to the
      * time of the main frame. */
     outlink->out_buf = outpicref = avfilter_ref_buffer(mainpic, ~0);
 
     av_dlog(ctx, "main_pts:%s main_pts_time:%s",
             av_ts2str(outpicref->pts), av_ts2timestr(outpicref->pts, &outlink->time_base));
     if (over->overpicref)
         av_dlog(ctx, " over_pts:%s over_pts_time:%s",
                 av_ts2str(over->overpicref->pts), av_ts2timestr(over->overpicref->pts, &outlink->time_base));
     av_dlog(ctx, "\n");
 

     ret = ff_start_frame(ctx->outputs[0], avfilter_ref_buffer(outpicref, ~0));

     over->frame_requested = 0;

     return ret;

 }
 
 static int try_start_next_frame(AVFilterContext *ctx)
 {
     OverlayContext *over = ctx->priv;
     AVFilterBufferRef *next_mainpic = ff_bufqueue_peek(&over->queue_main, 0);

     int ret;
 
     if (!next_mainpic)

         return AVERROR(EAGAIN);

     if ((ret = try_start_frame(ctx, next_mainpic)) == AVERROR(EAGAIN))
         return ret;

     avfilter_unref_buffer(ff_bufqueue_get(&over->queue_main));

     return ret;

 }
 
 static int try_push_frame(AVFilterContext *ctx)
 {
     OverlayContext *over = ctx->priv;

     AVFilterLink *outlink = ctx->outputs[0];

     AVFilterBufferRef *outpicref;

     int ret;

     if ((ret = try_start_next_frame(ctx)) < 0)
         return ret;

     outpicref = outlink->out_buf;
     if (over->overpicref)
         blend_slice(ctx, outpicref, over->overpicref, over->x, over->y,
                     over->overpicref->video->w, over->overpicref->video->h,
                     0, outpicref->video->w, outpicref->video->h);

     if ((ret = ff_draw_slice(outlink, 0, outpicref->video->h, +1)) < 0 ||
         (ret = ff_end_frame(outlink)) < 0)
         return ret;

     return 0;
 }
 

 static int flush_frames(AVFilterContext *ctx)

 {

     int ret;
 
     while (!(ret = try_push_frame(ctx)));
     return ret == AVERROR(EAGAIN) ? 0 : ret;

 }
 

 static int start_frame_main(AVFilterLink *inlink, AVFilterBufferRef *inpicref)

 {
     AVFilterContext *ctx = inlink->dst;
     OverlayContext *over = ctx->priv;

     int ret;

     if ((ret = flush_frames(ctx)) < 0)
         return ret;

     inpicref->pts = av_rescale_q(inpicref->pts, ctx->inputs[MAIN]->time_base,
                                  ctx->outputs[0]->time_base);

     if ((ret = try_start_frame(ctx, inpicref)) < 0) {
         if (ret != AVERROR(EAGAIN))
             return ret;

         ff_bufqueue_add(ctx, &over->queue_main, inpicref);

         av_assert1(inpicref == inlink->cur_buf);
         inlink->cur_buf = NULL;
     }

     return 0;

 }
 

 static int draw_slice_main(AVFilterLink *inlink, int y, int h, int slice_dir)

 {
     AVFilterContext *ctx = inlink->dst;

     OverlayContext *over = ctx->priv;

     AVFilterLink *outlink = ctx->outputs[0];
     AVFilterBufferRef *outpicref = outlink->out_buf;

     if (!outpicref)

         return 0;

     if (over->overpicref &&

         y + h > over->y && y < over->y + over->overpicref->video->h) {

         blend_slice(ctx, outpicref, over->overpicref, over->x, over->y,
                     over->overpicref->video->w, over->overpicref->video->h,
                     y, outpicref->video->w, h);
     }

     return ff_draw_slice(outlink, y, h, slice_dir);

 }
 

 static int end_frame_main(AVFilterLink *inlink)

 {

     AVFilterContext *ctx = inlink->dst;
     AVFilterLink *outlink = ctx->outputs[0];
     AVFilterBufferRef *outpicref = outlink->out_buf;
     flush_frames(ctx);

     if (!outpicref)

         return 0;
     return ff_end_frame(ctx->outputs[0]);

 }

 static int start_frame_over(AVFilterLink *inlink, AVFilterBufferRef *inpicref)

 {

     return 0;

 }

 static int end_frame_over(AVFilterLink *inlink)

 {

     AVFilterContext *ctx = inlink->dst;
     OverlayContext *over = ctx->priv;
     AVFilterBufferRef *inpicref = inlink->cur_buf;

     int ret;
 

     inlink->cur_buf = NULL;

     if ((ret = flush_frames(ctx)) < 0)
         return ret;

     inpicref->pts = av_rescale_q(inpicref->pts, ctx->inputs[OVERLAY]->time_base,
                                  ctx->outputs[0]->time_base);
     ff_bufqueue_add(ctx, &over->queue_over, inpicref);

     ret = try_push_frame(ctx);
     return ret == AVERROR(EAGAIN) ? 0 : ret;

 }

 static int request_frame(AVFilterLink *outlink)
 {
     AVFilterContext *ctx = outlink->src;
     OverlayContext *over = ctx->priv;
     int input, ret;
 
     if (!try_push_frame(ctx))
         return 0;
     over->frame_requested = 1;
     while (over->frame_requested) {
         /* TODO if we had a frame duration, we could guess more accurately */
         input = !over->overlay_eof && (over->queue_main.available ||
                                        over->queue_over.available < 2) ?
                 OVERLAY : MAIN;

         ret = ff_request_frame(ctx->inputs[input]);

         /* EOF on main is reported immediately */
         if (ret == AVERROR_EOF && input == OVERLAY) {
             over->overlay_eof = 1;

             if ((ret = try_start_next_frame(ctx)) != AVERROR(EAGAIN))
                 return ret;

             ret = 0; /* continue requesting frames on main */
         }
         if (ret < 0)
             return ret;
     }
     return 0;

 }
 

 static int null_draw_slice(AVFilterLink *inlink, int y, int h, int slice_dir)
 {
     return 0;

 }

 AVFilter avfilter_vf_overlay = {
     .name      = "overlay",
     .description = NULL_IF_CONFIG_SMALL("Overlay a video source on top of the input."),
 
     .init      = init,
     .uninit    = uninit,
 
     .priv_size = sizeof(OverlayContext),
 
     .query_formats = query_formats,
 

     .inputs    = (const AVFilterPad[]) {{ .name            = "main",
                                           .type            = AVMEDIA_TYPE_VIDEO,
                                           .get_video_buffer= get_video_buffer,
                                           .config_props    = config_input_main,

                                           .start_frame     = start_frame_main,
                                           .draw_slice      = draw_slice_main,
                                           .end_frame       = end_frame_main,

                                           .min_perms       = AV_PERM_READ | AV_PERM_WRITE | AV_PERM_PRESERVE },

                                         { .name            = "overlay",
                                           .type            = AVMEDIA_TYPE_VIDEO,
                                           .config_props    = config_input_overlay,

                                           .start_frame     = start_frame_over,

                                           .draw_slice      = null_draw_slice,

                                           .end_frame       = end_frame_over,

                                           .min_perms       = AV_PERM_READ | AV_PERM_PRESERVE },

                                         { .name = NULL}},
     .outputs   = (const AVFilterPad[]) {{ .name            = "default",
                                           .type            = AVMEDIA_TYPE_VIDEO,

                                           .rej_perms       = AV_PERM_WRITE,

                                           .config_props    = config_output,

                                           .request_frame   = request_frame, },

                                         { .name = NULL}},

     .priv_class = &overlay_class,

 };