lavfi/overlay: add logic for avoiding overlaying frames with PTS > main frame PTS

Also add debug logging messages for helping tracking down similar
issues.

Fix trac ticket #467.

libavfilter/version.h

@@ -30,7 +30,7 @@
 
 #define LIBAVFILTER_VERSION_MAJOR  2
 #define LIBAVFILTER_VERSION_MINOR 62
-#define LIBAVFILTER_VERSION_MICRO 100
+#define LIBAVFILTER_VERSION_MICRO 101
 
 #define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \
                                                LIBAVFILTER_VERSION_MINOR, \

libavfilter/vf_overlay.c

@@ -25,6 +25,8 @@
  * overlay one video on top of another
  */
 
+/* #define DEBUG */
+
 #include "avfilter.h"
 #include "libavutil/eval.h"
 #include "libavutil/avstring.h"
@@ -32,6 +34,7 @@
 #include "libavutil/pixdesc.h"
 #include "libavutil/imgutils.h"
 #include "libavutil/mathematics.h"
+#include "libavutil/timestamp.h"
 #include "internal.h"
 #include "drawutils.h"
 
@@ -75,7 +78,7 @@ typedef struct {
     uint8_t overlay_rgba_map[4];
     uint8_t overlay_has_alpha;
 
-    AVFilterBufferRef *overpicref;
+    AVFilterBufferRef *overpicref, *overpicref_next;
 
     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
@@ -146,6 +149,8 @@ static av_cold void uninit(AVFilterContext *ctx)
 
     if (over->overpicref)
         avfilter_unref_buffer(over->overpicref);
+    if (over->overpicref_next)
+        avfilter_unref_buffer(over->overpicref_next);
 }
 
 static int query_formats(AVFilterContext *ctx)
@@ -304,22 +309,31 @@ static void start_frame(AVFilterLink *inlink, AVFilterBufferRef *inpicref)
     AVFilterBufferRef *outpicref = avfilter_ref_buffer(inpicref, ~0);
     AVFilterContext *ctx = inlink->dst;
     OverlayContext *over = ctx->priv;
+    av_unused AVFilterLink *outlink = ctx->outputs[0];
 
     inlink->dst->outputs[0]->out_buf = outpicref;
     outpicref->pts = av_rescale_q(outpicref->pts, ctx->inputs[MAIN]->time_base,
                                   ctx->outputs[0]->time_base);
 
     if (!over->overpicref || over->overpicref->pts < outpicref->pts) {
-        AVFilterBufferRef *old = over->overpicref;
-        over->overpicref = NULL;
-        avfilter_request_frame(ctx->inputs[OVERLAY]);
-        if (over->overpicref) {
-            if (old)
-                avfilter_unref_buffer(old);
-        } else
-            over->overpicref = old;
+        if (!over->overpicref_next)
+            avfilter_request_frame(ctx->inputs[OVERLAY]);
+
+        if (over->overpicref && over->overpicref_next &&
+            over->overpicref_next->pts <= outpicref->pts) {
+            avfilter_unref_buffer(over->overpicref);
+            over->overpicref = over->overpicref_next;
+            over->overpicref_next = NULL;
+        }
     }
 
+    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");
+
     avfilter_start_frame(inlink->dst->outputs[0], outpicref);
 }
 
@@ -328,9 +342,11 @@ static void start_frame_overlay(AVFilterLink *inlink, AVFilterBufferRef *inpicre
     AVFilterContext *ctx = inlink->dst;
     OverlayContext *over = ctx->priv;
 
-    over->overpicref = inpicref;
-    over->overpicref->pts = av_rescale_q(inpicref->pts, ctx->inputs[OVERLAY]->time_base,
-                                         ctx->outputs[0]->time_base);
+    inpicref->pts = av_rescale_q(inpicref->pts, ctx->inputs[OVERLAY]->time_base,
+                                 ctx->outputs[0]->time_base);
+
+    if (!over->overpicref) over->overpicref      = inpicref;
+    else                   over->overpicref_next = inpicref;
 }
 
 // divide by 255 and round to nearest