1 files changed, 36 insertions, 0 deletions
diff --git a/libavfilter/video.c b/libavfilter/video.c
index 92b16b2b53..566b0ecb72 100644
--- a/libavfilter/video.c
+++ b/libavfilter/video.c
@@ -157,6 +157,42 @@ int ff_null_start_frame(AVFilterLink *link, AVFilterBufferRef *picref)
     return ff_start_frame(link->dst->outputs[0], buf_out);
 }
 
+// for filters that support (but don't require) outpic==inpic
+int ff_inplace_start_frame(AVFilterLink *inlink, AVFilterBufferRef *inpicref)
+{
+    AVFilterLink *outlink = inlink->dst->outputs[0];
+    AVFilterBufferRef *outpicref = NULL, *for_next_filter;
+    int ret = 0;
+
+    if ((inpicref->perms & AV_PERM_WRITE) && !(inpicref->perms & AV_PERM_PRESERVE)) {
+        outpicref = avfilter_ref_buffer(inpicref, ~0);
+        if (!outpicref)
+            return AVERROR(ENOMEM);
+    } else {
+        outpicref = ff_get_video_buffer(outlink, AV_PERM_WRITE, outlink->w, outlink->h);
+        if (!outpicref)
+            return AVERROR(ENOMEM);
+
+        avfilter_copy_buffer_ref_props(outpicref, inpicref);
+        outpicref->video->w = outlink->w;
+        outpicref->video->h = outlink->h;
+    }
+
+    for_next_filter = avfilter_ref_buffer(outpicref, ~0);
+    if (for_next_filter)
+        ret = ff_start_frame(outlink, for_next_filter);
+    else
+        ret = AVERROR(ENOMEM);
+
+    if (ret < 0) {
+        avfilter_unref_bufferp(&outpicref);
+        return ret;
+    }
+
+    outlink->out_buf = outpicref;
+    return 0;
+}
+
 static int default_start_frame(AVFilterLink *inlink, AVFilterBufferRef *picref)
 {
     AVFilterLink *outlink = NULL;