From f1dabc958e09978abdd71d3b7f1e05c742e54ab2 Mon Sep 17 00:00:00 2001
From: Michael Niedermayer <michael@niedermayer.cc>
Date: Sat, 25 Jun 2016 00:22:47 +0200
Subject: [PATCH] avfilter/dualinput: Add support to skip initial unpaired
 frames

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
---
 libavfilter/dualinput.c | 3 +++
 libavfilter/dualinput.h | 1 +
 2 files changed, 4 insertions(+)

diff --git a/libavfilter/dualinput.c b/libavfilter/dualinput.c
index 1a078a25e4..44750973a6 100644
--- a/libavfilter/dualinput.c
+++ b/libavfilter/dualinput.c
@@ -66,6 +66,9 @@ int ff_dualinput_init(AVFilterContext *ctx, FFDualInputContext *s)
         in[1].after = EXT_NULL;
         in[1].sync  = 0;
     }
+    if (s->skip_initial_unpaired) {
+        in[1].before = EXT_STOP;
+    }
 
     return ff_framesync_configure(&s->fs);
 }
diff --git a/libavfilter/dualinput.h b/libavfilter/dualinput.h
index 5ff23e6249..707b10c397 100644
--- a/libavfilter/dualinput.h
+++ b/libavfilter/dualinput.h
@@ -35,6 +35,7 @@ typedef struct {
     AVFrame *(*process)(AVFilterContext *ctx, AVFrame *main, const AVFrame *second);
     int shortest;               ///< terminate stream when the second input terminates
     int repeatlast;             ///< repeat last second frame
+    int skip_initial_unpaired;  ///< Skip initial frames that do not have a 2nd input
 } FFDualInputContext;
 
 int ff_dualinput_init(AVFilterContext *ctx, FFDualInputContext *s);