lavfi/overlay: implement shortest option

Force termination when the overlay stream ends. Simplify scripting logic,
for example when an infinite source is used to generate a background for
a composite video.

1 files changed, 4 insertions, 0 deletions

diff --git a/libavfilter/vf_overlay.c b/libavfilter/vf_overlay.c
index 7c615b4f20..857fbafb06 100644
--- a/libavfilter/vf_overlay.c
+++ b/libavfilter/vf_overlay.c
@@ -91,6 +91,7 @@ typedef struct {
     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
+    int shortest;               ///< terminate stream when the shortest input terminates
 
     char *x_expr, *y_expr;
 } OverlayContext;
@@ -102,6 +103,7 @@ 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 },
+    { "shortest", "force termination when the shortest input terminates", OFFSET(shortest), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, 1, FLAGS },
     {NULL},
 };
 
@@ -560,6 +562,8 @@ static int request_frame(AVFilterLink *outlink)
         /* EOF on main is reported immediately */
         if (ret == AVERROR_EOF && input == OVERLAY) {
             over->overlay_eof = 1;
+            if (over->shortest)
+                return ret;
             if ((ret = try_filter_next_frame(ctx)) != AVERROR(EAGAIN))
                 return ret;
             ret = 0; /* continue requesting frames on main */