@@ -1485,11 +1485,19 @@ Overlay one video on top of another.

 It takes two inputs and one output, the first input is the "main"

 video on which the second input is overlayed.

-It accepts the parameters: @var{x}:@var{y}.

+This filter accepts the following parameters:

+

+@table @option

+

+@item x

+The horizontal position of the left edge of the overlaid video on the main video.

+

+@item y

+The vertical position of the top edge of the overlaid video on the main video.

+

+@end table

-@var{x} is the x coordinate of the overlayed video on the main video,

-@var{y} is the y coordinate. The parameters are expressions containing

-the following parameters:

+The parameters are expressions containing the following parameters:

 @table @option

 @item main_w, main_h

@@ -1515,15 +1523,15 @@ Follow some examples:

 @example

 # draw the overlay at 10 pixels from the bottom right

 # corner of the main video.

-overlay=main_w-overlay_w-10:main_h-overlay_h-10

+overlay=x=main_w-overlay_w-10:y=main_h-overlay_h-10

 # insert a transparent PNG logo in the bottom left corner of the input

-avconv -i input -i logo -filter_complex 'overlay=10:main_h-overlay_h-10' output

+avconv -i input -i logo -filter_complex 'overlay=x=10:y=main_h-overlay_h-10' output

 # insert 2 different transparent PNG logos (second logo on bottom

 # right corner):

 avconv -i input -i logo1 -i logo2 -filter_complex

-'overlay=10:H-h-10,overlay=W-w-10:H-h-10' output

+'overlay=x=10:y=H-h-10,overlay=x=W-w-10:y=H-h-10' output

 # add a transparent color layer on top of the main video,

 # WxH specifies the size of the main input to the overlay filter

@@ -34,6 +34,7 @@

 #include "libavutil/pixdesc.h"

 #include "libavutil/imgutils.h"

 #include "libavutil/mathematics.h"

+#include "libavutil/opt.h"

 #include "internal.h"

 #include "video.h"

@@ -63,30 +64,18 @@ enum var_name {

 #define OVERLAY 1

 typedef struct {

+    const AVClass *class;

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

     int max_plane_step[4];      ///< steps per pixel for each plane

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

-    char x_expr[256], y_expr[256];

+    char *x_expr, *y_expr;

     AVFrame *main;

     AVFrame *over_prev, *over_next;

 } OverlayContext;

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

-{

-    OverlayContext *over = ctx->priv;

-

-    av_strlcpy(over->x_expr, "0", sizeof(over->x_expr));

-    av_strlcpy(over->y_expr, "0", sizeof(over->y_expr));

-

-    if (args)

-        sscanf(args, "%255[^:]:%255[^:]", over->x_expr, over->y_expr);

-

-    return 0;

-}

-

 static av_cold void uninit(AVFilterContext *ctx)

 {

     OverlayContext *s = ctx->priv;

@@ -358,6 +347,23 @@ static int request_frame(AVFilterLink *outlink)

     return output_frame(ctx);

 }

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

+#define FLAGS AV_OPT_FLAG_VIDEO_PARAM

+static const AVOption options[] = {

+    { "x", "Horizontal position of the left edge of the overlaid video on the "

+        "main video.",          OFFSET(x_expr), AV_OPT_TYPE_STRING, { .str = "0" }, .flags = FLAGS },

+    { "y", "Vertical position of the top edge of the overlaid video on the "

+        "main video.",          OFFSET(y_expr), AV_OPT_TYPE_STRING, { .str = "0" }, .flags = FLAGS },

+    { NULL },

+};

+

+static const AVClass overlay_class = {

+    .class_name = "overlay",

+    .item_name  = av_default_item_name,

+    .option     = options,

+    .version    = LIBAVUTIL_VERSION_INT,

+};

+

 static const AVFilterPad avfilter_vf_overlay_inputs[] = {

     {

         .name         = "main",

@@ -391,10 +397,10 @@ 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),

+    .priv_class = &overlay_class,

     .query_formats = query_formats,